How Accurate Are Tests to Detect Coronavirus on Surfaces?

Science
جمعه 26 اردیبهشت 1399 ساعت 12:56
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Smith sonian mag
Even before California went on lockdown thanks to the COVID-19 pandemic, MacKenzie Smith, the head librarian at the University of California, Davis, was concerned. The roughly 400,000 square feet of library space she oversees is filled with books and other items that constantly change hands — and could help spread SARS-CoV-2, the coronavirus that causes COVID-19.
Smith and her colleagues wanted to know if they should implement self-checkout stations, quarantine books upon return, and ramp up cleaning and disinfecting efforts. “There are a million questions,” she says. And there are no official guidelines. So together with Jonathan Eisen, a UC Davis evolutionary biologist who studies how viruses and other microbes interact with their environments, Smith began to work on her own guidelines, sketching a plan for testing surfaces such as desks, doorknobs, and books.
And while corporate behemoths like Amazon and Smithfield Foods scramble to develop new safety and testing procedures in response to major outbreaks in their facilities, Smith’s concerns echo the worries of people who manage relatively smaller spaces across the country, including building managers, teachers, restaurateurs, and hoteliers.
The Centers for Disease Control and Prevention says it may be possible for people to contract COVID-19 by touching contaminated surfaces or objects and then touching their mouth, nose, or even eyes, although many experts don’t think this is the main way the coronavirus spreads. As more states and cities lift stay-at-home orders and more businesses, campuses, and public spaces reopen, how can we be sure they aren’t harboring infectious traces of coronavirus?
With no official protocols for monitoring public spaces, several academic labs and private companies are working on tests — some in the research stages and others that are already offered for sale, sometimes at high prices.
But while scientists may be focused on how and where the virus has spread, people who run businesses and other organizations want to know whether the spaces they manage and use are safe on a daily basis. That basic question has no easy answer, because testing for viral presence on surfaces is far from simple. The tests vary a lot; they can be very expensive, take days to get results, and provide only a limited amount of useful information, if any at all. Despite the uncertainty, some organizations are already looking at the possibility of running such tests — even if it’s just for peace of mind.
The biggest testing hurdle is being able to tell the difference between a viable “live” virus, which can infect a person, and traces of viral RNA, the genetic material the virus leaves behind as it degrades, which can’t sicken anyone. And while scientists do have the tools to distinguish between the two, that level of analysis won’t be available to the average shopkeeper or restaurant owner. “That will be a big challenge,” says Andrea Silverman, who studies urban engineering and public health at New York University’s Tandon School of Engineering and College of Global Public Health. “Detecting the RNA does not necessarily mean that you have an infectious virus.”
Viruses can linger on surfaces, from cafe counters to water fountains to bathroom sinks, and coronavirus is no exception. For instance, preliminary research published in the New England Journal of Medicine in April, suggests viable coronavirus can stay on plastic and stainless steel for 72 hours, cardboard for 24 hours, and copper for four hours. Research in The Lancet published around the same time found that infectious virus survived on the outer layer of a surgical mask for a week.
To dig into the coronavirus’s longevity, both research teams swabbed various surfaces to collect potential particles and grew the virus in the lab, inside host cells. “That’s the gold standard,” says Silverman — if the viruses can multiply and grow inside cells, they are infectious.
But growing viruses that can afflict humans can be dangerous and requires facilities with extensive safety features — called biosafety level 3 labs — in which scientists wear full-body hazard suits and other protective gear . Such tests require highly trained personnel and specialized equipment, so biosafety labs are mostly found in research institutions, which everyday businesses can’t easily access. “The labs that are doing cell culture for the SARS-CoV-2 are really busy,” Silverman says, “They don’t have the bandwidth for a lot of samples from people from the community.” And given their specialized nature, such tests would also likely be too expensive for the average business.
For more accessible testing, most people have to resort to the next best thing: checking for the presence of viral RNA. This requires machines that use a process called polymerase chain reaction (PCR), which makes many copies of small bits of the genetic material to make it easier to run tests that can identify where it came from. But because this test can’t tell with certainty if the testing area contains infectious virus, or just traces of its genetic material, this approach can lead to false positives, Eisen says.
“Even if you detect the RNA you don’t know if your virus is still ‘live’ on the surface or not,” Silverman says. “And that impacts whether this environment is quote-unquote safe.” For librarians like Smith, viral RNA tests won’t show whether her books have infectious traces of the virus on them. Restaurateurs wanting to know whether their tables are safe to seat patrons for dinner won’t get a clear answer, either.
That doesn’t mean viral RNA tests are useless — they are just better suited for epidemiology studies, says Eisen. For instance, the tests could show how the virus spreads and pinpoint hotspots.
This could help identify super-shedders — patients who spew more of the virus compared to others, says Jack Gilbert, professor of pediatrics at the University of California, San Diego, who studies how microbes travel around and has been sampling local hospitals to investigate what makes one a super shedder. “We want to determine variance in patients — how much RNA they leave behind in a room,” he says.
Scientists can also build the coronavirus’s family tree by analyzing viral RNA from different locations. As viruses mutate into new strains, their RNA changes, so scientists can find their spot on the family tree and figure out where a particular version of the virus originated.
Tracing mutations can even reveal whether employees picked the virus up in their workplace or elsewhere, Eisen says. His team is starting to work on this in hospitals, he adds “to figure out if health care workers are picking it up from the hospitals or the community.” That nuance is key for some employees who get sick with COVID-19 — when they are infected at work, they qualify for workers’ compensation benefits.
But testing surfaces people come in contact with for viral RNA has some value, Eisen says. Similarly to how health workers test public beaches for the presence of harmful bacteria, some communal areas may benefit from coronavirus monitoring. If, for example, an office kitchen that had no coronavirus traces last week suddenly shows high amounts, someone who is using the kitchen is infected. So countertop traces can be informative. “You still don’t know if you have ‘live’ virus or not,” Silverman says. “But you at least have a sense of what happened in your space, whether the organism has been brought in.”
Several academic research groups and companies are already testing surfaces for coronavirus. In addition to the studies led by Eisen and Gilbert, researchers at Weill Cornell Medicine in New York have been looking at the potential spread of coronavirus in New York City’s subway system. For a week before the city went on lockdown, Christopher Mason, a geneticist at Weill Cornell, and his team swabbed handrails, kiosks, and floors in the Grand Central and Times Square stations — two of the city’s busiest. The researchers then tried several types of tests to detect the virus. Surprisingly, the 86 samples they collected didn’t seem to contain viable coronavirus.
But Mason’s experiments may have coincided with extensive cleaning efforts from the Metropolitan Transit Authority, the entity that manages the subway, which may have wiped out traces of the virus.
Despite the uncertainty of viral-RNA tests, some companies are already offering services for high-traffic areas within buildings. “Some businesses may have risk-management teams or insurance companies that will require them to do testing,” says Dan Ventura, owner of Hawk Environmental Services in Seattle, which tests for a variety of hazards from mold to bacteria to asbestos and has recently added coronavirus to the list. Ventura says that if several employees fall ill, managers may want to thoroughly clean the facility and then use the tests to prove there is no detectable viral RNA. Others may ramp up their cleaning procedures upon finding RNA where it hasn’t been before. The testing, he adds, “will allow these buildings to stay open, stay running, and provide a second level of assurance.”
But the tests can take several days to process, which may make the results moot, says Gilbert, and by then people may already have been infected. “Why not just increase your cleaning procedures?” he adds.
To shorten the wait time, Ventura offers expedited testing — at a price. Hawk will ship swabbing kits to customers, which then go to a third-party lab. (Ventura declined to name the lab, citing worry that it would be inundated by requests and suffer processing bottlenecks.) The cost ranges from $365 per swab with a four-day turnaround time to $605 per swab for a 24-hour turnaround — prices that Ventura says are “affordable when looked at through the lens of liability of the operation.”
How many swabs are needed is unclear, and there are no clear guidelines. Ventura says he leaves it to businesses to decide how many to use and the size of the sampling areas. In academic labs, the appropriate number of swabs also varies, since scientists define their methods to fit specific research goals. Silverman cites one non-coronavirus example in which her team used one swab for roughly a square foot of surface area, but other researchers may do things differently. “It’s not totally clear how it would translate to a coffee shop,” she says, but a shopkeeper will still need multiple swabs since “you can’t use one swab for every surface.”
Testing for viral RNA in a university lab, especially in large batches, is significantly cheaper. “The raw cost per sample is probably ten dollars,” Eisen says. Nonetheless, Ventura says he’s getting upwards of 10 calls a day from companies potentially interested in testing.
Other companies are offering equipment to help test for coronavirus, including Aanika Biosciences in Brooklyn. Aanika is developing a way for companies to trace and authenticate their supply chains by tagging products with a harmless microbe, which can serve as a biological barcode. To detect the microbial DNA, Aanika uses chemical methods and equipment that can also be used to detect coronavirus RNA, says biologist Ellen Jorgensen, the company’s chief scientific officer.
In March, Jorgensen called New York City officials to offer help with testing coronavirus in buildings. The company’s pricing isn’t set yet, but Jorgensen also offered to do free testing for New York schools. So far the city only sent her a form to fill out and she hasn’t heard anything else. “As time goes on I might try again,” she says.
ChaiBio , a biotech company in Santa Clara, California is selling test equipment directly to businesses, which would eliminate long waits for test results. Traditional PCR machines used in research labs can cost $200,000, but ChaiBio sells versions for less than $10,000. Originally developed for the food industry, the machines are used by brewers to detect bacteria that spoil beer.
When COVID-19 arrived, ChaiBio developed a process to test for the new coronavirus. A starter pack for the virus costs $8,500 and includes the machine, swabs, and other testing materials. Using the ChaiBio machine doesn’t require a degree in biology and takes less than an hour, says CEO and cofounder Josh Perfetto. Unlike traditional PCR machines, which look for the virus’s entire sequence of RNA, ChaiBio’s looks for the genetic pieces specific only to the organism of interest, which cuts time, complexity, and cost. “You put your sample in the device and it gives you the result on the computer screen,” he says.
But the idea of someone with no training running coronavirus tests on their own worries academics like Gilbert, who notes that it still takes a degree of expertise to run these tests, including how to calibrate the machines and how to handle the samples. The results, he adds, are complex and can be open to interpretation — another task that could prove difficult for a layperson.
The process is “not for an office worker or someone at home who wants to swab their door handle,” Gilbert says, because there is too much possibility for error. A safer approach to reopening businesses and public areas, he says, is simply practicing social distancing, wearing protective gear like masks and gloves, and proper sanitizing.
As for the library at UC Davis, Smith wants to know whether patrons and staff can safely pass books back and forth once campus reopens, and whether she has to buy UV-sanitizing equipment, since libraries, with their stacks of delicate books and other materials, can’t be sterilized with harsh chemicals and steam. So she and Eisen are planning a pilot study, swabbing books to determine how quickly the coronavirus decays, how they should quarantine books with different types of covers, and how often custodians should clean doorknobs and other surfaces.
“We are not going to reopen the space until we have figured it out,” she says. “We are sort of breaking new ground here.”
Lina Zeldovich is a science writer and editor. She has written for Newsweek , The Atlantic , Smithsonian , Audubon , Nature , Scientific American , and more.
This article was originally published on Undark . Read the original article .
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