In a perfect world, the entrance to every office, restaurant and school would offer a coronavirus test – one with a real error, and able to instantly find out who was virus-free and safe. admitted and who, with advanced disease, should be turned away.
That fact does not exist. But while the country is struggling to regain a view of normal life amid the uncontrolled spread of the virus, some scientists believe a quick test with just a little more could on a paper strip of paper we close.
The test does not look for the virus itself, nor can it diagnose infection. Instead, he scrambles for one of Covid-19’s trademarks: loss of sense of smell. Since last spring, many researchers have come to recognize the signal, also known as anosmia, as one of the best symptoms of chronic coronavirus disease, which can affect even people who are not. identify a sick feeling.
People who get the coronavirus cannot have a flagella test and not develop symptoms at all. But in a study not yet published in a scientific journal, a mathematical model showed that sniff-based experiments, if administered extensively and frequently, could find enough cases to significantly slow down transmission.
Daniel Larremore, a public health researcher at the University of Colorado, Boulder, and lead author of the study, confirmed that the work of his team was still purely theoretical. Although some odor tests are already used in clinical and research settings, the results tend to be expensive and laborious to use and are not widely available. And in the context of the pandemic, real-world data do not yet support the effectiveness of odor tests as a frequent screen for the coronavirus. Because there are so many test kits that have sustained pandemic control efforts so far, some experts have been skeptical that odor tests could be widely spread, or done enough to deceive, in order to reduce the spread of infection.
“I have been heavily involved in pushing to recognize odor loss as a hallmark of Covid-19 from the beginning,” said Dr. Claire Hopkins, an ear, nose and throat surgeon at Guy and St. Louis Hospitals. Thomas in the United Kingdom and the author of a recent report on the subject in the Lancet. “But I don’t see any value in a screening test. ”
Reliable odor testing offers many potential benefits. It could capture far more cases than the fever tests, which have largely become screening tools for Covid-19. Studies have found that about 50% to 90% of people who are positive for the coronavirus experience a measurable level of odor loss, as a result of the virus damaging when it attacks cells in the airway.
“It’s really like having the virus act in the nose right now,” said Danielle Reed, associate director of the Monell Chemical Sensing Center in Philadelphia. “It adds to the amount of information you get from other tests. Last month, Reed and her colleagues at Monell presented a study, not yet published in a scientific journal, outlining a possible rapid odor test for screening for Covid-19.
In contrast, only a minority of people with Covid-19 end up spinning temperature. Fever also tends to persist, and anosmia can persist for many days.
A smell test could also come with an attractive low price tag, perhaps as low as 50 cents per card, said Derek Toomre, a cell biologist at Yale University and author of the Larremore paper. Toomre hopes his version fits the bill. The test, the U-Smell-It test, is a small smorgasbord of smelling scratch-and-sniff covered on paper cards. Test takers pick up at scent wells, infiltrate and punch their beats into a smartphone app, firing to make an accurate measurement of co. at least three of the five smells. Different cards have a different smell, so there is no answer key for memory.
Toomre thought the test could take less than a minute. It’s also a manufacturer’s dream, he said: “One printer could do” 50 million of these tests every day. ” Such numbers, he said, could make big teeth in a country hampered by a lack of widespread access to tests that look directly for pieces of the coronavirus.
In their study, Larremore, Toomre and their colleague, Roy Parker, a biochemist at the University of Colorado, Boulder, created such a scenario by using computing devices. Administered daily or almost daily, an odor screen that captured at least 50% of new infections was able to break out almost as well as a more accurate and slower laboratory test that was passed. take only once a week.
Such tests, Larremore said, could act as an entry – point screen on college campuses or in offices, possibly in conjunction with a rapid virus test. There may even be a place for them in the home, if researchers can find a way to reduce abuse.
“I think this is a sight to behold,” said Dr. Carol Yan, an ear, nose and throat specialist at the University of California, San Diego. “Testing people again will be a valuable part of this. ”
Toomre is seeking emergency use permit for the U-Smell-It from the Food and Drug Administration, and has partnered with several organizations in Europe and elsewhere to test it under real-world conditions.
However, changing theory from practice will present many challenges. Smell tests that reliably identify people with coronavirus, while excluding people who are ill with something else, are not yet widely available. (Hopkins identified a couple of tests for odor, developed before the pandemic, that cost about $ 30 per head and remain in a limited supply.) If they were ever rolled out, they would certainly miss some people with a disease and, unlike tests that look for the virus itself could not diagnose a disease on its own.
And odor loss, such as fever, is not prohibitive for Covid-19. Other diseases can damage a person’s sense of smell. So can allergies, nasal congestion from the common cold, or just the process of aging. About 80% of people over the age of 75 have some degree of odor loss. Some people are born anosmic.
Furthermore, in many cases of Covid-19, odor loss can lie long after the virus has gone and humans are no longer infectious – a problem that some people may land in Covid Post-Purgatory if forced to rely on scent screens to resume activity, Yan said.
There are also many ways to design an odor-based screen. Smells associated with food that is popular in some countries but not in others, such as bubble gum or licorice, may affect test results for some people. People who have grown up in very urban areas may not recognize smells from nature, such as pine or freshly cut grass.
Smell is also not a binary sense, hard on or off. Reed suggested a step in which testers assess the severity of a test odor – recognizing that the coronavirus can significantly reduce but not eliminate odor sensitivity.
But the more complex the test, the more difficult it will be to manufacture and use quickly. And no test, even a perfectly designed one, would work with 100% accuracy.
Dr. Ameet Kini, a pathologist at Loyola University Medical Center, pointed out that odor tests would not be free of the problems associated with other types of tests, such as poor compliance or refusal to separate.
Smell screens are “probably better than nothing,” Kini said. “But no test is going to stop the pandemic unless it is combined with other measures.”