上海贵族宝贝自荐419

The future of disease tracking is going down the drain — literally. Flushed with success over detecting coronavirus in wastewater, and even specific variants of SARS-CoV-2, the virus that causes COVID-19, researchers are now eyeing our collective poop to monitor a wide variety of health threats.

Before the pandemic, wastewater surveillance was a smaller field, primarily focused on testing for drugs or mapping microbial ecosystems. But these researchers were tracking specific health threats in specific places — opioids in parts of Arizona, polio in Israel — and hadn’t quite realized the potential for national or global public health.
Then COVID-19 hit.

The pandemic triggered an “incredible acceleration” of wastewater science, says Adam Gushgari, an environmental engineer who before 2020 worked on testing wastewater for opioids. He now develops a range of wastewater surveillance projects for Eurofins Scientific, a global laboratory testing and research company headquartered in Luxembourg.

A subfield that was once a few handfuls of specialists has grown into more than enough scientists to pack a stadium, he says. And they come from a wide variety of fields — environmental science, analytical chemistry, microbiology, epidemiology and more — all collaborating to track the coronavirus, interpret the data and communicate results to the public. With other methods of monitoring COVID-19 on the decline, wastewater surveillance has become one of health experts’ primary sources for spotting new surges.

Hundreds of wastewater treatment plants across the United States are now part of COVID-19 testing programs, sending their data to the National Wastewater Surveillance System, or NWSS, a monitoring program launched in fall 2020 by the U.S. Centers for Disease Control and Prevention. Hundreds more such testing programs have launched globally, as tracked by the COVIDPoops19 dashboard run by researchers at the University of California, Merced.

In the last year, wastewater scientists have started to consider what else could be tracked through this new infrastructure. They’re looking at seasonal diseases like the flu, recently emerging diseases like bird flu and mpox, formerly called monkeypox, as well as drug-resistant pathogens like the fungus Candida auris. The scientists are even considering how to identify entirely new threats.

Wastewater surveillance will have health impacts “far broader than COVID,” predicts Amy Kirby, a health scientist at the CDC who leads NWSS.

But there are challenges getting from promise to possible. So far, such sewage surveillance has been mostly a proof of concept, confirming data from other tracking systems. Experts are still determining how data from our poop can actually inform policy; that’s true even for COVID-19, now the poster child for this monitoring. And they face public officials wary of its value and questions over whether, now that COVID-19 health emergencies have ended, the pipeline of funding will be cut off.

This monitoring will hopefully become “one of the technologies that really evolves post-pandemic to be here to stay,” says Mariana Matus, cofounder of Biobot Analytics, a company based in Cambridge, Mass., that has tested sewage for the CDC and many other health agencies. But for that to happen, the technology needs continued buy-in from governments, research institutions and the public, Matus and other scientists say.

How wastewater testing works
Wastewater-based epidemiology has a long history, tracing back at least to physician John Snow’s 1850s observations that cholera outbreaks in London were connected to contaminated water.
In the 1920s and ’30s, scientists began to take samples from sewage and study them in the lab, learning to isolate specific pathogens that cause disease. These early researchers focused on diseases that spread through contaminated water, such as polio and typhoid.

Today, automated machines typically retrieve sewage samples. The machines used to collect waste beneath maintenance hole covers are “like R2-D2 in terms of size” or smaller, says Erin Driver, an environmental engineer at Arizona State University in Tempe who works on collection methods.

Driver can plug this machine, or a larger version used for sampling at wastewater treatment plants, into a water pipe and program it to pull a small amount of sewage into an empty bottle at regular intervals, say, once an hour for 24 hours. She and colleagues are developing smaller versions of the automated sampler that could be better suited for more targeted sampling.

What happens in the lab to that bottle of waste depends on what scientists are testing for. To test for opioids and other chemicals, scientists might filter large particles out of the sample with a vacuum system, extract the specific chemicals that they want to test, then run the results through a spectrometer, an instrument that measures chemical concentrations by analyzing the light the chemicals give off.

To determine levels of SARS-CoV-2 or another virus, a scientist might separate liquid waste from solid waste with a centrifuge, isolate viral genetic material, and then test the results with a PCR machine, similar to testing someone’s nose swab. Or, if scientists want to know which SARS-CoV-2 variants are present, they can put the material through a machine that identifies a variety of genetic sequences.

Would the coronavirus even show up in waste?
In the panicked early days of the pandemic, an urgent basic question loomed. “Will this even work?” remembers Marlene Wolfe, an environmental microbiologist at Emory University in Atlanta. While polio is spread through fecal matter, there were early hints that the coronavirus mostly spreads through the air; scientists initially weren’t even sure that it would show up in sewage.

On the same day in 2020 that the San Francisco Bay Area went on lockdown, Wolfe and colleagues at Stanford University, where she was based at the time, got a grant to find out. The team was soon spending hours driving around the Bay Area to collect sewage samples, “navigating lockdown rules” and negotiating special permissions to use lab space, she says.

“We were anxiously waiting to see if our first samples would show a positive result for SARS-CoV-2,” Wolfe says.

Not only did the sewage samples test positive, Wolfe and her colleagues found that coronavirus levels in the Bay Area’s wastewater followed the same trends as reported cases, the team reported in December 2020 in Environmental Science & Technology. When case counts went up, more virus appeared in the sewage, and vice versa. Early projects in other parts of the country showed similar results.
More than three years later, data on reported cases have become much less reliable. Fewer people are seeking out lab-based PCR tests in favor of easier-to-access at-home tests — with results often not reported. Wastewater trends have become the best proxy to provide early warnings of potential new COVID-19 surges, such as the increased spread this summer, to health officials and the public alike.

Opening the tracking floodgates
In summer 2022, wastewater tracking got a new chance to prove itself. Mpox was rapidly spreading globally, including in the United States. But tests were limited, and the disease, which was spreading primarily through intimate contact between men, quickly drew social stigma, leading some people to hesitate in seeking medical care.

Within a few weeks of the start of the U.S. outbreak, Wolfe and her colleagues, as well as research teams at Biobot and other companies, had developed tests to identify mpox in sewage.

Just as scientists had seen with COVID-19, mpox trends in wastewater matched trends in official case numbers. In California, wastewater results even suggested that the disease may have spread farther than data from doctors’ offices suggested, Wolfe and collaborators reported in February in the New England Journal of Medicine.

Like COVID-19, mpox doesn’t transmit through the water, but sewage testing still picked up the virus. The early results from that summer outbreak convinced some health officials that wastewater technology could be used for many diseases, no matter how they spread, Matus says.
Scientists are starting to find more and more infectious diseases that can be tracked in sewage. “Honestly, everything that we’ve tried so far has worked,” says Wolfe, who is now a principal investigator of WastewaterSCAN, a national sewage testing project led by researchers at Stanford and Emory. The project team currently tests samples for six different viruses and is working on other tests that it can send out to the more than 150 sites in its monitoring network.

Through an informal literature review of pathogens important for public health, scientists at Biobot found that previous research had identified 76 out of 80 of them in wastewater, stool or urine, suggesting that those pathogens could be monitored through sewage. The list ranges from the chicken pox virus to the microbes that cause sexually transmitted diseases like chlamydia to the tickborne bacteria that cause Lyme disease.

Finding focus
With this much opportunity, the question on many researchers’ minds is not, “What can we test for?” but “What should we test for?”

In January, a report put out by the National Academies of Sciences, Engineering and Medicine came up with three criteria. The pathogen should threaten public health. It should be detectable in wastewater. And it should generate data that public health agencies can use to protect their communities.

Given all the threats and hints of what can be found in wastewater, the first two criteria don’t narrow the field too much. So for now, researchers are taking cues from state and local public health officials on which pathogens to prioritize.

Biobot is working on tests for common diseases like the flu, RSV, hepatitis C and gonorrhea. And the CDC has its eye on some of the same common pathogens, as well as strategies for tracking antimicrobial resistance, a threat that has increased during the pandemic as health systems have been under strain.

Even if they choose the perfect targets, though, researchers also have to figure out how to generate useful data. For now, that’s a sticking point.

How to use the data
Tracking pathogens is one thing. But determining how the results correspond to actual numbers of sick people is another, even in the case of COVID-19, where researchers now have years of detailed data. As a result, many public health officials aren’t yet ready to make policy decisions based on poop data.

In New York City over the last three years, for example, the local government has poured more than $1 million into testing for COVID-19, mpox and polio in sewage from the city’s water treatment plants. But the city’s health department hasn’t been using the resulting data to inform local COVID-19 safety measures, so it’s unclear what’s being done with the data.
Health officials are used to one swab per person, says Rachel Poretsky, a microbiologist at the University of Illinois Chicago. She also heads wastewater monitoring for the city of Chicago and the state of Illinois.

Public health training relies on identifying individual sick people and tracing how they became ill. But in wastewater surveillance, one data point could represent thousands of sick people — and the data come from the environment, rather than from hospitals and health clinics. What to do next when positive results turn up isn’t as obvious.

Numbers collected from the health care system always represent patients, so a spike indicates a surge in cases. In the case of sewage data, however, environmental factors like weather, local industries and the coming and going of tourists also can create “weird outliers” that resist easy interpretation, Poretsky says. For instance, a massive rainstorm might dilute samples, or chemical runoff from a factory might interfere with a research team’s analytical methods.

Data interpretation only gets more complicated when scientists begin testing wastewater for an increasing number of health threats. Every pathogen’s data need to be interpreted differently.

With coronavirus data, for example, wastewater tests consistently come back positive, so interpreting the data is all about looking for trends: Are viral concentrations going up or down? How does the amount of virus present compare with the past? A spike in a particular location might signal a surge in the community that hasn’t yet been picked up by the health care system. The community might respond by boosting health resources, such as opening vaccine clinics, handing out free masks and at-home tests, or adding staff to local hospital emergency departments.

Mpox, on the other hand, has infected far fewer people, and positive tests have been rare after last summer’s outbreaks ended. Now, researchers are simply watching to see whether the virus is present or absent in a given sewershed.

“It’s more about having an early warning,” Matus says. If a sewershed suddenly tests positive for mpox after negative results for the last few months, health officials might alert local doctors and community organizations to look out for anyone with symptoms, aiming to identify any cases and prevent a potential outbreak.

Another complicated pathogen is C. auris, a fungus that has developed resistance to common drugs. It can spread rapidly in health care settings — and be detected in sewage. Researchers from Utah and Nevada reported in February in Emerging Infectious Diseases that it was possible to track C. auris in the sewage from areas experiencing outbreaks.

If hospitals or health officials could identify the presence of this fungus early, that information could guide public health actions to curb outbreaks, says Alessandro Rossi, a microbiologist at the Utah Public Health Laboratory in Salt Lake City. But interpreting the warnings isn’t as clear-cut for C. auris as for viruses.

The fungus can grow in sewage after it leaves health care facilities, Rossi says. The pathogen has “the potential to replicate, form biofilms and colonize a sewershed.” In other words, C. auris can create its own data interference, potentially making wastewater results seem worse than they really are.
Moving wastewater into the future
Most current testing programs are reactive. By looking at health threats one at a time using specific PCR tests, the programs mostly confirm that pathogens we already are worrying about are getting people sick.

But some scientists, like Wim Meijer, envision a future in which wastewater monitoring wades into the unknown and alerts us to unusual disease outbreaks. The microbiologist, of the University College Dublin, heads Ireland’s wastewater surveillance program. Ideally, in this ahead-of-the-curve future, after detecting something alarming in sewage, his team could closely collaborate with health officials to study the pathogen and, if necessary, start combating the threat.

One idea for turning the tech proactive is to prepare for new health threats that we can see coming. For example, Meijer and his colleagues are interested in screening Ireland’s sewage for the H5N1 bird flu, but they are not yet doing this testing.

Another approach takes advantage of genetic testing technology to look at everything in our waste. Kartik Chandran, an environmental engineer at Columbia University who has mapped sewers’ microbial ecosystems with this technique, describes it as “trying to shine the light more broadly” rather than looking where the light is already shining brightest.

Such an approach might identify new pathogens before sick people start going to the doctor’s office, potentially leading to an earlier public health response. But with health officials still unsure of how best to use wastewater data, much more basic research is needed first.
“People think wastewater surveillance is the answer to everything, and clearly that’s not true,” says Kirby, of the CDC, reflecting concerns from the state and local officials that she collaborates with at NWSS. Before diving ahead into proactive surveillance, Kirby and her colleagues are working to set up basic wastewater standards and protocols for health agencies. Priorities include evaluating how sewage trends correlate to cases for different pathogens and developing standards for how to use the data.

The wastewater surveillance field also needs to keep growing if the goal is to monitor and contribute to global health, with more sites contributing data and more scientists to analyze it. All of this work requires sustained funding.

The CDC’s program so far has been funded by COVID-era legislation and will run out of money in 2025. While wastewater surveillance is more cost-effective than other types of testing, it still requires a lot of resources. Washington’s state health department, for example, paid Biobot more than $500,000 for a one-year sewage testing contract, while the CDC has paid the company more than $23 million since 2020 for its work with NWSS.

For the last few years, wastewater surveillance has been a giant, messy group project. Scientists have collaborated across fields and locations, across private and public institutions, through Zoom calls and through poop samples shipped on ice. They’ve shown that waste might hold the key to a new way of tracking our collective health.

A lot of unanswered questions remain, and it could be some time before your local sewer can tell you exactly what disease risks you might be facing. But COVID-19 pushed thousands of experts to look into their toilets and start asking those questions. “Now, everyone’s a believer,” says Driver, of ASU. “Everyone’s doing the work.”

Great tits use syntax to compose their tunes.

Japanese great tits (Parus minor) communicate using at least 10 different notes on their own and in combination. Researchers played different calls for Japanese great tits in a forest in Nagano, Japan, to see how the birds responded — an indication of what the call might mean. The birds responded differently to individual notes than they did when played the same note in combination with other notes. And, when researchers reversed the note order, the birds didn’t respond the same way.
By itself, a note means one thing to great tits, but in combination, it means something different, the team argues March 8 in Nature Communications. Similarly, among humans, the order of words in a sentence, its compositional syntax, matters.

Some primates combine calls to convey different messages, but individual notes don’t carry unique meaning in these species. Great tits are the first nonhuman species shown to use compositional syntax, the researchers write.
In this recording, researchers played three types of calls for Japanese great tits: First, a call with three notes — A, B, and C — which signals danger; second, a one-note call (D), which attracts mates; and finally, a combination call, ABC-D, which causes the birds to scan the skies for predators and fly to the source of the sound.
Researchers played an ABC-D call for great tits, and then reversed an ABC-D call. Birds responded differently in each case.

Bees may need their own supplemental protein shakes as increasing carbon dioxide in the atmosphere saps the nutritional quality of pollen.

Pollen collected from plants gives bees their only natural source of protein (nectar is a sugar-shot for energy). Yet protein content in pollen of a widespread goldenrod species (Solidago canadensis) dwindled by a third, from about 18 percent to 12 percent, over 172 years, according to analysis of recently collected flowers and of preserved specimens at the Smithsonian Institution’s National Museum of Natural History. During those same years, CO2 concentrations in the atmosphere increased from about 280 parts per million to 398 ppm, researchers report April 12 in Proceedings of the Royal Society B.
The same themes also showed up in two years of growing the goldenrod at CO2 concentrations up to 500 ppm. More CO2 meant less concentrated protein in pollen, say Lewis Ziska of the U.S. Department of Agriculture’s Bee Research Laboratory in Beltsville, Md., and his colleagues.

“It’s like you’re eating a starchier diet — what would that do to us?” says study coauthor Joan Edwards of Williams College in Williamstown, Mass. “Bees aren’t so different.”

Bees, wild or domesticated, need adequate protein to feed their larvae, maintain their immune systems and for many more functions, says bee biologist Cédric Alaux of the French agricultural research agency INRA in Avignon. Canada goldenrod is an example of a species known to offer pollen that can be stored to tide honeybees over the winter. The one-third decrease in protein concentration reported in the new study is big enough to shorten bee life spans, he says.

Lower quality in bee food sources could be contributing to global bee declines observed in recent years and the uncertain state of pollination for crops, Edwards says. “The health of the bee population is not just for the flowers and the bees and biodiversity, but also for human health and well-being.”

Buying a handgun in Connecticut means waiting — lots of waiting. First comes an eight-hour safety course. Then picking up an application at a local police department. Review of the application (which includes a background check and fingerprinting) can take up to eight weeks. If approved, the state issues a temporary permit, which the buyer trades in at state police headquarters for a permanent one. Then it’s back to the store for the gun.

Head west to Missouri, though, and buying a handgun is practically a cakewalk. Customers at Osage County Guns in Belle, Mo., for example, can walk into the store and walk out with a gun if they pass the FBI’s instant background check, says John Dawson, the store’s chief technical officer.
“If a person knew exactly what they wanted,” he says, the store could, “in theory, complete the transaction in about 15 minutes.”

Missouri and Connecticut have staked out opposite ends of the gun law spectrum. Connecticut didn’t require handgun buyers to get a permit until 1995. Missouri had a tough law on the books, but repealed it in 2007. The states’ laws have flip-flopped, making for a fascinating natural experiment on gun laws’ effects on gun violence.

The states “had mirror image policy changes, and mirror image results,” says Daniel Webster, a health policy researcher at Johns Hopkins University.

Flipping the laws was associated with 15 percent fewer gun suicides in Connecticut and 16 percent more in Missouri, a statistical analysis by Webster and colleagues, published last year in Preventive Medicine, estimated. Similar analyses by Webster in 2014 and 2015 indicated a 40 percent reduction in Connecticut gun homicide numbers, and an 18 percent rise in Missouri.
The evidence is very suggestive, says Harvard University researcher David Hemenway. But it’s not extensive enough to persuade everyone — or to move national policy.

In fact, questions loom about the impact of all sorts of policies, from background checks to assault weapons bans to gun buybacks. That’s partly because gun research faces roadblocks at every turn: Scientists have to deal with data shutouts, slashed funding and, occasionally, harassment.

For a few questions, however, researchers have come up with solid answers: There’s a convincing link between gun availability and gun suicide, for one. And studies from the United States and abroad suggest that some gun laws do rein in gun violence. To make firm conclusions, though, scientists are desperate for more data.

But the U.S. Centers for Disease Control and Prevention can’t collect gun data like it used to, and information about guns used in individual crimes is locked up tight. Under current federal laws, Hemenway says, “It’s almost impossible for researchers to get even the data that are available.”

Locked up
In a squat brick building tucked in the hills of Martinsburg, W. Va., gun data are overflowing.

Thousands of cardboard boxes, stacked high in tidy columns, line the hallways of the federal government’s National Tracing Center. In the parking lot, steel shipping containers hold even more boxes. Each box contains about 2,000 pages of gun purchase records. To trace a gun, the center’s employees often search through these records by hand.

That’s their job: tracking when and where guns used in crimes were originally purchased, and by whom. It’s a huge undertaking: In 2015, the center, part of the Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF, received more than 373,000 gun trace requests from law enforcement.
Such a mass of data is a researcher’s dream. But current laws keep gun traces secret. The agency shares traces only with law enforcement. The public can see just summaries or aggregate data.

Webster has used this data to paint a rough picture of how Missouri’s repeal affected the flow of guns to criminals. In 2006, when buying a handgun required a permit, 56.4 percent of guns recovered by police had been originally sold by a Missouri gun dealer. In 2012, five years after the state nixed the permit requirement, the number rose to 71.8 percent, Webster and colleagues reported in the Journal of Urban Health in 2014.

The findings suggest that it’s easier now for criminals in Missouri to get their hands on legally purchased guns. But Webster can’t say for certain whether more guns are moving to criminals — or whether legal gun owners are committing more crimes. For that, he’d need to see the individual gun traces.

About a decade ago, researchers who wanted such detailed data could get it. “We’d just hand them a DVD,” says ATF information specialist Neil Troppman. “Those days are long over.”

A handful of laws snarl the process, from how a gun trace begins to who can see the data.

One big hitch in the system: Police officers who find a gun at a crime scene can’t always look up the owner’s name on a computer. That’s because there is no national registry — no searchable database of guns and their owners. To set one up would be illegal. So police have to submit a request to the tracing center, which tracks the gun’s movement from manufacturer or importer to dealer. Then the ATF can ask the dealer who bought the gun. If the dealer has gone out of business, ATF employees dig for the answer themselves, in old gun purchase records stockpiled at the tracing center. The process takes an average of five days. And after law enforcement gets the data, federal law makes sure no one else can see it.

Federal constraints
In 2003, Congress unleashed a beast of a bill with an amendment that effectively tore out the ATF’s tongue. The Tiahrt amendment was the first in a series of provisions that drastically limited the agency’s ability to share its crime gun data — no giving it to researchers, no making it public, no handing it over under Freedom of Information Act requests (the public’s channel for tapping into information from the federal government).

Funding for gun control research had dried up a few years earlier. There’s no outright ban, but a 1996 amendment had nearly the same effect. It’s known as the Dickey amendment, and it barred the CDC from using funds to “advocate or promote gun control.” According to a 2013 commentary in JAMA, that meant almost any research on guns.
If the 1996 law’s language was vague, Congress made the message clear by cutting the CDC’s budget by $2.6 million — exactly the same amount the agency had spent the previous year on gun violence research. The funds were later reinstated, but earmarked for other things. So the CDC largely backed off, except for some basic tallying, says spokesperson Courtney Lenard, because of the funding cuts and because Congress “threatened to impose further cuts if that research continued.”

In 2011, Congress hit the National Institutes of Health with similar restrictions. About a year later, President Obama tried to ease the choke hold: He ordered the CDC to research the causes and prevention of gun violence, and called on Congress to provide $10 million in funding. Finally, 17 years after the CDC cuts, news reports proclaimed that the ban had been lifted and research could resume. But Congress never authorized the money, and the CDC remained on the sidelines. This April, nearly 150 health and science organizations, universities and other groups signed a letter urging Congress to restore the CDC’s funding.

Meanwhile, research on gun violence and gun control trudges forward: Researchers can sometimes convince law enforcement agencies to share data on guns linked to crimes, and grants can come from private foundations. Yet even with limits on research, the science in some cases is solid: A gun in the home, for example, increases the odds a person will commit suicide by about 3-to-1. Here, Hemenway says, “The weight of the evidence is overwhelming.”

But how to use laws to reduce gun violence remains hotly contested, and opinions among the public, and even scientists, are polarized.

Critics of gun control laws think the matter is clear: Again and again studies show that gun control policies just don’t work, says economist John Lott, who has written extensively on the subject. Take background checks, he says, “Given that these laws are costly, you’d like to believe there’s some evidence that they produce a benefit.”

Webster acknowledges the divisive split in opinions. “The vast majority of people are on one side of the fence or the other,” he says. “They’ll point to a study that is convenient to their political arguments and call it a day.”

Bad for your health
For researchers who manage to navigate the legal tangles and funding troubles of gun research, actually doing the research itself isn’t easy.

Unlike clinical trials in medicine, where scientists can give, for example, a cholesterol drug to half a study’s participants and then compare the effects between users and nonusers, scientists studying gun violence can’t dole out new handguns to one group and none to another and see what happens.

Instead, researchers turn to observational studies. That means looking at how — and if — suicides track with gun ownership in different groups of people and over time, for example. Finding a link between two observations doesn’t necessarily mean they’re connected. (People have linked the yearly number of Nicolas Cage movies to swimming pool drownings, after all.) But finding a lot of links can be telling.

For suicides, the link to gun access holds strong — among old people, young people, women, adolescents, “you name it,” Hemenway says. Lots of guns means lots of suicides by gun, he says.
In 2007, Hemenway and colleagues examined gun ownership rates and statewide suicide data from 2000 to 2002. People in states with a high percentage of gun owners (including Wyoming, South Dakota and Alaska) were almost four times as likely to kill themselves with guns as people living in states with relatively few gun owners (such as Hawaii, Massachusetts and Rhode Island), the researchers reported in the Journal of Trauma Injury, Infection and Critical Care.

More recently, a 2013 study in Switzerland compared suicide rates before and after an army reform that cut the number of Swiss soldiers by half. After the reform, fewer people had access to army-issued guns — and the suicide rate dipped down by about two per 100,000 men age 18–43. That’s about 30 men each year who didn’t die from suicide, the study’s authors estimated in the American Journal of Psychiatry.

A 2014 review of 16 such studies, published in the Annals of Internal Medicine, came to the same conclusion, again: Access to guns meant higher risk of suicide.

“The evidence is unassailable,” says Stanford University criminologist John Donohue. “It’s as strong as you can get.”

Mental illness factors into suicide too, says Jeffrey Swanson, a medical sociologist at Duke University. (Some 21 to 44 percent of suicides reported to the CDC are committed by people with mental health problems.) And federal laws aren’t particularly good at keeping guns away from mentally ill people. A 1968 law prohibits gun sales to a narrow slice of people with a history of mental illness, but it’s easy for others to slip through the cracks. Even people the law does target can end up with guns — because states don’t have to report mental health records to the FBI’s national background-check system.

“You’ve got tons of records that would disqualify people from buying guns,” Swanson says, but they don’t necessarily make it into the system.
Even if the United States had a perfect mental health care system and cured schizophrenia and bipolar disorder and depression, he says, the overall problem of gun violence would still exist. Mentally ill people just aren’t that violent toward others, Swanson noted in the Annals of Epidemiology in 2015. In fact, people with mental illness committed fewer than 5 percent of U.S. gun killings between 2001 and 2010, according to the CDC.

“People think that in order to fix gun violence, we need to fix the mental health care system,” Swanson says. That’s wrong, he argues. “It’s a diversion from talking about guns.”

Weak laws
After Sandy Hook, San Bernardino and other high-profile mass shootings, people have been talking about what gun control laws, if any, actually work.

Unfortunately, there’s just not enough evidence to make strong conclusions about most laws, Hemenway says. In 2005, for example, a federal task force reviewed 51 studies of gun laws, mostly in the United States, and came up empty-handed. The task force couldn’t say whether any one of the laws made much of a difference. The efficacy of U.S. gun laws is hard to pin down for two main reasons, Hemenway says: Gun laws aren’t typically very strong, and studies tend to look at overall effects on violence.

One major study published in JAMA in 2000 analyzed suicide and homicide data from 1985 to 1997 to evaluate the impact of the Brady Act, a 1994 federal law that requires background checks for people buying guns.

Eighteen states and the District of Columbia already followed the law. So researchers compared suicide and homicide rates with those in the 32 states new to the law. If Brady curbed gun violence, those 32 states should see dips in deaths.
That didn’t happen (with one exception: Gun suicides in those states dropped in people age 55 and older — by about 1 per 100,000 people).

“I don’t think anybody was really shocked,” Webster says. After all, Brady had a gaping hole: It didn’t require background checks for guns bought from private sellers (including those at gun shows). The loophole neutered Brady: People who didn’t want a background check could simply find a willing private seller. That’s just too easy, Webster says: It’s like letting people decide whether they want to go through the metal detector at the airport.

Like the Brady Act, the 1994 Federal Assault Weapons Ban didn’t seem to do much to prevent violence, criminologist Christopher Koper and colleagues concluded in a 2004 report to the U.S. Department of Justice. The law, which expired in 2004, imposed a 10-year ban on sales of military-style semiautomatic guns. These weapons fire one bullet per trigger squeeze and have features like threaded barrels (which can be used for screwing on silencers) or barrel mounts (for attaching bayonets). The 1994 law also banned most large-capacity magazines (storage devices that feed guns more than 10 rounds of ammo).

But like Brady, the ban came with a catch: It didn’t apply to weapons and magazines made before September 13, 1994. That’s a lot of exemptions. At the time, the United States had more than 1.5 million assault weapons and nearly 25 million guns with large-capacity magazines, reported Koper, of George Mason University in Fairfax, Va.

“The more complete the bans are, the better the effects seem to be,” Donohue says. Take Australia: In 1996, the country enacted strict laws and a gun buyback program after a mass shooting killed 35 people in Tasmania. The ban made certain long-barreled guns illegal (including semiautomatic rifles and pump-action shotguns — weapons that let people fire lots of rounds quickly), and the country bought back and destroyed more than 650,000 guns.

With the law, Donohue says, “Australia effectively ended the problem of mass shootings.”

And as economists Christine Neill and Andrew Leigh found, the law drastically cut down the number of gun suicides, too.
Tough laws
Eleven years after Australia launched its tough gun control legislation, Neill, of Wilfrid Laurier University in Canada, and Leigh, then at Australian National University in Canberra, announced that the law might actually be saving lives.

Critics attacked. One petitioned Neill’s university to reprimand her. Then they came for Leigh’s e-mails. He had to hand over any that mentioned firearms or guns. Had there been anything improper — any whiff that the researchers were biased — Neill believes gun advocates would have pounced.

Neill and Leigh, now an Australian politician, had uncovered telling changes in different regions’ suicide rates between 1990–1995 and 1998–2003. “Firearms suicides fell most in Tasmania, by a long shot,” Neill says, almost 70 percent, the team later reported in 2010 in the American Law and Economics Review.

Australia’s law, called the National Firearms Agreement, or NFA, applied to all of the country’s states and territories, but some had more guns than others. Tasmania, for example, had the most guns bought back, Neill says: 7,302 guns per 100,000 people. More guns bought back meant bigger drops in suicide rates, she says.
Instead, the United States goes for smaller laws, fashioned mostly state-by-state. Still, some may be effective. Blocking domestic violence offenders’ access to guns seems to cut down on homicides, for example. From 1982 to 2002, states with restraining order laws that bar offenders from buying guns had rates of intimate partner homicide that were 10 percent lower than in states lacking the laws, researchers reported in 2006 in Evaluation Review.It’s a stark result, and suggests that tough laws can have big impacts. Australia “did an outright ban and something akin to a confiscation of guns,” Webster says. “That’s never going to happen in the United States.”

In 2010, Webster and colleagues reported similar results at the city level. He and colleagues tracked intimate partner homicides from 1979 to 2003 in 46 U.S. cities. Those that made it hard for people with domestic violence restraining orders to get guns had 19 percent fewer intimate partner homicides compared with cities with less stringent laws, the team reported in Injury Prevention.

“These are pretty consistent findings,” Webster says. Those state policies seem to be working.

Conclusions about other, more well-known laws, such as “right-to-carry,” are less convincing. Such laws, which allow people to carry concealed handguns in public, could offer people a means of defense. Or they could make it easier for people in an argument to whip out a gun.
“The findings are all over the map,” Hemenway says. A report from the National Research Council in 2005 found no causal link between right-to-carry laws and crime. It also concluded that people do use guns to protect themselves (say, by threatening or shooting an attacker) but how often is hard to say. Estimates vary from 100,000 to 2.5 million times per year in the United States.

Economist Mark Gius of Quinnipiac University in Hamden, Conn., estimated that restricting people’s right to carry boosts a state’s murder rate by 10 percent, he reported in 2014 in Applied Economics Letters.

Donohue’s 2014 results lean a different way. The Stanford researcher updated the NRC analysis with more than a decade of new data and found that laws letting people carry concealed weapons boost violent crime — a bit. Based on data from 1979 to 2012, his statistical modeling showed that a state with a right-to-carry law would experience 8 percent more aggravated assaults than a state without such a law, for example.

“More and more evidence is amassing that these laws are harmful,” Donohue says, but he concedes that there’s still uncertainty. “I’m not quite ready to say that we’ve nailed it down.”

Less uncertainty would require more analyses and more data. But in this field, even that doesn’t guarantee consensus.

“The problem is that there are many ways to slice the data,” Donohue says. “Almost nothing is as clear as the advocates make it — on both sides.”

Shaken-but-not-stirred remnants of Earth’s earliest years still exist nearly 4.6 billion years later.

Researchers traced the shadowy footprints of an isotope that hasn’t existed for over 4.5 billion years to much younger lava rocks from the Pacific and Atlantic oceans. That suggests that reservoirs of the ancient mantle may be hidden deep inside the planet, geochemist Hanika Rizo and colleagues report May 13 in Science.

Earth formed about 4.6 billion to 4.5 billion years ago as planetary bodies collided, disintegrating and melting to accrete into one mass like a hot, rocky lint ball. Geologists have assumed that any relics of this bumpy beginning were mixed beyond recognition.
Instead, Rizo’s team found a surprise: Some modern flood basalts have unusually high concentrations of tungsten-182. That’s significant because that isotope forms only from radioactive decay of hafnium-182. And hafnium-182 only existed during Earth’s first 50 million years. “These isotopes had to be created early,” says Rizo, of the University of Quebec in Montreal.
It is “spectacular” that some of Earth’s earliest materials may still be preserved, says Matthias Willbold, a geochemist at the University of Manchester in England. “We may have to revise our view of the Earth’s internal structure.”

Rizo and colleagues measured the tungsten-182 in flood basalts from two locations: Canada’s Baffin Bay, part of the 60-million-year-old North Atlantic Igneous Province, and near the Solomon Islands, part of the 120-million-year-old Ontong Java Plateau in the Pacific Ocean. “Flood basalts are not normal eruptions,” Rizo says. “They are capable of tapping into the deep mantle.”
Her team found that levels of tungsten-182 in the lavas varied, suggesting that the deep sources of these younger rocks were different pieces of Earth’s oldest material, each with their own isotopic signature and history. These results also show that the ancient remnants have somehow escaped being mixed by convection currents.

Geophysicists have identified two large “blobs” in the deep mantle, called large low-shear velocity provinces. Those blobs “could be candidates” for the remnants of the ancient mantle, Rizo says.

What builds up can also tear down, a new study of bacteria suggests.

Bacteria build biofilms, communities of the microorganisms encased in a protective goo that shields the microbes from antibiotics and immune system attacks. But the very enzymes bacteria use to construct that shield can also destroy some of its molecules and strip away the protection, researchers report May 20 in Science Advances.

“We’re weaponizing the bacteria against themselves,” says P. Lynne Howell, a structural microbiologist at the Hospital for Sick Children in Toronto. Howell and colleagues studied Pseudomonas aeruginosa bacteria, which can cause pneumonia and other infections and is particularly problematic for people with the lung disease cystic fibrosis.
The researchers discovered that two enzymes, PelAh and PslGh, which the bacteria use to build two different sugar polymers, can degrade those same polymers. That delete function, supplied by parts of the enzymes known as glycoside hydrolase domains, normally helps correct mistakes or prevents buildup of the sugar chains inside bacterial cells, Howell says.

In laboratory tests, synthetic versions of the glycoside hydrolase domains applied to P. aeruginosa cultures stopped the bacteria from forming new biofilms and melted existing ones. Stripping away sugar polymers did not kill the bacteria but did make them more vulnerable to antibiotics and immune cells. Human lung cells grown in dishes containing the enzymes suffered no harm, suggesting the enzymes wouldn’t damage human tissues.

Animal tests are needed to determine whether the enzymes are safe and can fight biofilm infections in the body, Howell says. Similar enzymes from other bacteria and fungi may also fight biofilm infections caused by those organisms, she says.

Giant pandas have better ears than people — and polar bears. Pandas can hear surprisingly high frequencies, conservation biologist Megan Owen of the San Diego Zoo and colleagues report in the April Global Ecology and Conservation.

The scientists played a range of tones for five zoo pandas trained to nose a target in response to sound. Training, which took three to six months for each animal, demanded serious focus and patience, says Owen, who called the effort “a lot to ask of a bear.”

Both males and females heard into the range of a “silent” ultrasonic dog whistle. Polar bears, the only other bears scientists have tested, are less sensitive to sounds at or above 14 kilohertz. Researchers still don’t know why pandas have ultrasonic hearing. The bears are a vocal bunch, but their chirps and other calls have never been recorded at ultrasonic levels, Owen says. Great hearing may be a holdover from the bears’ ancient past.

Even if you’ve never lived in rattlesnake territory, you know what the sound of a snake’s rattle means: Beware! A shake of its rattle is an effective way for a snake to communicate to a potential predator that an attack could result in a venomous bite.

For more than a century, scientists have posited how that rattle might have evolved. The rattle is composed of segments of keratin (the same stuff that makes up human hair), and specialized muscles in a snake’s tail vibrate those segments rapidly to create the rattling sound. The rattlesnake’s rattle is a trait that evolved only once in the past and is now found in only two closely related genera of snakes that live in North and South America. But plenty of other species of snakes also vibrate their tails as a warning to potential predators.

Bradley Allf and colleagues at the University of North Carolina in Chapel Hill think that the tail vibration and the evolution of the rattle might be connected. They gathered 155 snakes of 56 species — 38 species from the Viperidae family, which includes rattlesnakes, and 18 species from the largest snake family, Colubridae — from museums, zoos and private collectors. Working with captive snakes let them control conditions, such as temperature, that can affect tail vibration. With each snake, one of the researchers tried to get it to behave defensively by waving a stuffed animal in front of it. The team videotaped the snakes as they vibrated their tails, or not.

The researchers plotted the snakes’ tail vibration duration and rate against how closely related a species was to rattlesnakes. One group of snakes that lives in the Americas was taken out of the analysis because its tail vibrations were so similar to those of rattlesnakes; it appears that these species are mimicking the dangerous snakes that live near them (not a bad strategy for survival). Among the rest of the snakes analyzed, those that were more closely related had tail behavior that was more similar to that of rattlesnakes.

“Our results suggest that tail vibration by rattleless ancestors of rattlesnakes may have served as the signal precursor to rattlesnake rattling behavior,” the researchers write in the October issue of the American Naturalist. “If ancestral tail vibration was a reliable cue to predators that a bite was imminent, then this behavior could have become elaborated as a defensive signal.”

Allf and his colleagues propose a couple of ways that this could have happened. Perhaps snakes that made noise with their tails were better at startling predators, and this may have prompted such noise-making tail features to spread and eventually become refined into what is now a rattle. Or maybe snakes that shook their tails longer and faster developed calluses of keratin. If these calluses provided better warning, that may have somehow evolved into a rattle.

“Thus, the rattlesnake rattle might have evolved via elaboration of a simple behavior,” they conclude.

The first time Jessica Cantlon met Kumang at the Seneca Park Zoo, the matriarch orangutan regurgitated her previous meal right into Cantlon’s face. “I was retching,” Cantlon recalls. “It was so gross.” But Cantlon was there to kick off a series of behavioral experiments, and her students, who would be working with Kumang regularly, were watching. “Does anyone have any towels?” she remembers asking, knowing she had to keep her cool.

Cantlon’s deliberate nature and whatever-it-takes attitude have served her well. As a cognitive neuroscientist at the University of Rochester in New York, she investigates numerical thinking with some of the most unpredictable and often difficult study subjects: nonhuman primates, including orangutans, baboons and rhesus macaques, and — most remarkably — children as young as age 3. Both groups participate in cognitive tests that require them, for example, to track relative quantities as researchers sequentially add items to cups and to distinguish between quantities of assorted dots on touch screens. The kids also go into the functional MRI scanner where, in a feat impressive to parents everywhere, they lie completely still for 20 to 30 minutes so Cantlon and colleagues can get pictures of their brains.
“She takes steps carefully, and she thinks very hard about where she is going,” says Daniel Ansari, a developmental cognitive neuroscientist at the University of Western Ontario in London, Canada, who is familiar with Cantlon’s work. “She goes for the big questions and big methodological challenges.”

The central question in Cantlon’s research is: How do humans understand numbers and where does that understanding come from? Sub-questions include: What are the most primitive mathematical concepts? What concepts do humans and other primates share? Are these shared concepts the foundation for fancier forms of mathematical reasoning? In addressing these questions, Cantlon draws on a wide range of methods. “Very few people can combine work on cognitive skills — studies from the point of view of behavior — with imaging work in very young children, and very few people do that same combination in nonhuman primates,” says Elissa Newport, who chaired the brain and cognitive sciences department at Rochester for more than a decade and now leads the Center for Brain Plasticity and Recovery at Georgetown University.

As a graduate student, Cantlon determined that neuroimaging studies would add an independent source of data to the cognitive questions under exploration in Elizabeth Brannon’s lab at Duke University. So she identified collaborators and taught herself functional MRI. “By the time she graduated, she had something like four dissertations’ worth of work,” says Brannon, now of the University of Pennsylvania.

In the years since, Cantlon has identified a type of “protocounting” in baboons; they can keep tabs on approximate quantities of peanuts as researchers increase those quantities (SN Online: 5/17/15). In her most attention-grabbing work, Cantlon studied activity in the brains of children while they watched Sesame Street clips that dealt with number concepts — an unexpected success that proved everyday, relatively unaltered stimuli can yield meaningful data. An ongoing study in Cantlon’s lab seeks to find out how monkeys, U.S. kids and adults, and the Tsimané people of Bolivia, who have little formal education, distinguish between quantities. Do they determine the number of dots presented on the computer screen or do they rely on a proxy such as the total area covered by the dots?
The work explores how the brain understands everyday concepts, but it could also inform strategies in math education. “If we understand the fundamental nature of the human brain and mind, that might give us a better insight into how to communicate number concepts to kids,” Cantlon says.

Growing up outside of Chicago, Cantlon enjoyed digging deep into a topic and becoming an expert. She and a friend turned themselves into ice skating superfans one summer, reading up on the Olympic skaters and checking videos out of the local library. In another project, Cantlon decided to learn everything possible about the price of gold. When she moved to a school where she could no longer take Latin, she taught and tested herself. Despite the fact that neither of her parents went to college, no one ever questioned that Cantlon would go. She studied anthropology as an undergraduate at Indiana University in Bloomington. “I was interested in the question of where we come from,” Cantlon says. “I was interested in studying people.”
During college, she went on an archaeological dig in Belize and studied lemurs in Madagascar. For a year after graduation, she observed mountain gorillas in Rwanda, detailing their behavior every 10 minutes. “What they were thinking was something that was constantly on my mind,” she says. “‘How are we similar? Are you thinking what I’m thinking?’” Though she might have succeeded in any number of careers, she wanted exploration to be a big part of her life: “I don’t think doing a less exotic type of work would have been as satisfying.”

Today, Cantlon, who at age 40 recently earned tenure, doesn’t spend much time in the field. And even in the lab, she leaves much of the data collection to her graduate students and research assistants. “At this point, we are a well-oiled system,” she says, referring to the brain scan studies on kids.
To make the kids comfortable, Cantlon’s team does trial runs in a mock scanner, describing it as a spaceship and providing “walkie-talkies” for any necessary communication. To keep them interested, the researchers treat it as a team activity and offer a ton of positive reinforcement, with prizes including Lego sets and a volcano-making kit. The kids receive pictures of their brains, which typically interest the parents most. The older of Cantlon’s two daughters, a 5-year-old extrovert named Cloe, has participated in behavioral tests and will no doubt be excited for her first brain scan.

The Sesame Street study was in part inspired by a paper by Uri Hasson, a neuroscientist at Princeton University who imaged the brains of volunteers while they watched The Good, the Bad and the Ugly. To better understand brain development, Cantlon wanted to see how brain activity compared in kids and adults exposed to math in a natural way. Of particular interest was a region called the intraparietal sulcus, or IPS, thought to play a role in symbolic number processing. The results, reported in PLOS Biology in 2013, showed that kids with IPS activity more closely resembling adults’ activity performed better on mathematical aptitude tests.

“It was the clearest, cleanest — did not have to come out this way — result,” Cantlon says.

Cantlon is notable for her diverse set of tools, says Steve Piantadosi, a computational neuroscientist and colleague at Rochester. “But she has something which is even more powerful than that. If you have different hypotheses and you want to come up with the perfect experiment that distinguishes them, that is something she is very good at thinking about. She is a great combination of critical and creative.”

To add another methodological approach, Cantlon next plans to collaborate with Piantadosi to develop computational models that explain the operations the brain performs as it counts or compares quantities. She would also like to add data analyses from wild primates into the mix. When researchers talk about the evolution of a primitive number sense, they often speak about foraging activity — identifying areas of the forest with more food, for example. But Cantlon wonders whether social interactions also require some basic understanding of quantities.

As for a recent question from a colleague about what risky project she’ll pursue now that she has tenure, Cantlon says nothing in particular comes to mind: “I feel like we’ve been doing the crazy things all along.”

ORLANDO, Fla. — New evidence from separate labs supports the controversial idea that an overlooked and unexpected Culex mosquito might spread Zika virus.

The southern house mosquito, Culex quinquefasciatus, is common in the Americas. Constância Ayres, working with Brazil’s Oswaldo Cruz Foundation in Recife, previously surprised Zika researchers with the disturbing proposal that this mosquito might be a stealth spreader of Zika. But two U.S. research groups tested the basic idea and couldn’t get the virus to infect the species.
Now, preliminary results from Ayres’ and two other research groups are renewing the discussion. The data, shared September 26 at the International Congress of Entomology, suggest that Zika can build up in the house mosquito’s salivary glands — a key step in being able to transmit disease. Basic insect physiology is only part of the puzzle, though. Even if the mosquitoes prove competent at passing along Zika, there remain questions of whether their tastes, behavior and ecology will lead them to actually do so.

In the current outbreak, the World Health Organization has focused on mosquitoes in a different genus, Aedes, particularly Ae. aegypti, as the main disease vector. But Ayres had announced months ago the discovery of the virus in Brazil’s free-flying house mosquitoes (SN Online: 7/28/16).

At the congress, Ayres’ foundation colleague Duschinka Guedes reported that captive mosquitoes fed Zika-tainted blood had virus growing in their own guts and salivary glands within days. The virus doesn’t spread every time a mosquito slurping contaminated blood gets virus smeared on its mouthparts, though. To move from the mosquito to what it bites, viruses have to infect the insect midgut, then travel to the salivary glands and build up enough of a population for an infective dose drooling into the next victim. When Guedes offered the infected mosquitoes a special card to bite, they left telltale virus in the salivary traces, a sign of what they could do when biting — and infecting — a real animal.

Researchers from China and Canada who were not originally on the symposium program also stepped up to share their results, some of which are unpublished. Some tasks are still in early stages, but both labs showed Zika virus building up in some kind of Culex mosquitoes.

At the Beijing Institute of Microbiology and Epidemiology, Tong-Yan Zhao found the virus peaking in the house mosquitoes eight days after their first contaminated drink. As a test of the infectious powers of the mosquitoes, researchers let the Zika-carrying insects bite baby lab mice. Later, the virus showed up in the brains of eight out of nine lab mice. The results were reported September 7 in Emerging Microbes & Infections.
From Brock University in St. Catharines, Canada, Fiona Hunter has found signs that 11 out of 50 wild-caught Culex pipiens pipiens mosquitoes picked up the virus somewhere on their bodies. So far, she has completely analyzed one mosquito and reports that the virus was indeed in its saliva.

These positive results contradict Culex tests at the University of Texas Medical Branch in Galveston. Those tests, with U.S. mosquitoes, found no evidence that C. quinquefasciatus can pick up and pass along a Zika infection, says study coauthor Scott Weaver. Stephen Higgs of Kansas State University in Manhattan and his colleagues got similar results. “We’re pretty good at infecting mosquitoes,” Higgs says, so he muses over whether certain virus strains won’t infect mosquitoes from particular places.

The main risk from Culex at the moment is distraction, warned Roger Nasci of North Shore Mosquito Abatement District in Northfield, Ill. After the talks, he rose from the audience to say that Ae. aegypti is a known enemy and limited resources should not be diverted from fighting it.

George Peck, who runs mosquito control for Clackamas County in Oregon, isn’t convinced that the high virus concentrations dosing the test mosquitoes are realistic. Yet he’s watching the issue because like much of northern North America, Clackamas doesn’t have the Ae. aegypti vector to worry about. But it does have plenty of Culex mosquitoes.