In a perfect world, the entrance to every office, restaurant and school would offer a coronavirus test — one with absolute accuracy that could instantly determine who was safe to admit and who should be turned away.
That reality does not exist. But some scientists think that a quick test involving a stinky strip of paper might at least get us close.
The test does not look for the virus, nor can it diagnose disease. Rather, it screens for one of Covid-19’s trademark signs: the loss of the sense of smell. Since last spring, researchers have come to recognize the symptom, also known as anosmia, as one of the best indicators of an ongoing coronavirus infection.
In a study that has not yet been published in a scientific journal, a mathematical model showed that sniff-based tests, if administered sufficiently widely and frequently, might detect enough cases to substantially drive transmission down.
Daniel Larremore, an epidemiologist at the University of Colorado, Boulder, and the study’s lead author, stressed that his team’s work was still purely theoretical. In the context of the pandemic, there is not yet real-world data to support the effectiveness of smell tests as a frequent screen for the coronavirus.
But a reliable smell test offers potential benefits. It could catch far more cases than fever checks, which have largely flopped as screening tools for Covid-19. Studies have found that about 50 to 90 percent of people who test positive for the coronavirus experience some degree of measurable smell loss, a result of the virus wreaking havoc when it invades cells in the airway.
A smell test could also come with an appealingly low price tag, perhaps as low as 50 cents per card, said Derek Toomre, a cell biologist at Yale University and an author on Dr. Larremore’s paper. Dr. Toomre hopes that his version will fit the bill. The test, the U-Smell-It test, is a small smorgasbord of scratch-and-sniff scents arrayed on paper cards. People taking the test pick away at wells of smells, inhale and punch their answers into a smartphone app.
Dr. Toomre is seeking an emergency use authorization for U-Smell-It from the Food and Drug Administration, and has partnered with groups in Europe and elsewhere to trial the test under real-world conditions.