When Carthage College students begin returning to campus in Kenosha, Wisconsin, next week, two very non-traditional welcome back gifts will await them: a thermometer, and a scratch-and-sniff smell test card.
Temperature checks as a way to quickly provide a gauge for a common symptom of the novel coronavirus aren’t exactly uncommon in the United States. But smell tests are relative newcomers to the screening scene. Both will be part of daily self-monitoring at the liberal arts college.
“Losing your sense of smell is an early symptom—sometimes the only symptom—of COVID,” Leslie Cameron, a psychology professor and expert on sensory perception at Carthage, told The Daily Beast. “We should be testing for it.”
Carthage is among a growing number of schools, businesses, and other institutions looking to leverage growing knowledge of how COVID-19 can wreak havoc on the olfactory system to make something resembling safe reopening possible. Studies have found that the majority of coronavirus patients have at least some loss to their sense of smell or taste, often starting early in the course of the disease. In fact, science now suggests that smell loss may be more predictive of COVID-19 than a fever, currently the go-to target for screening from China to California. Researchers are also finding that the symptom is more common among young people and in milder cases of the disease—categories that can, but do not always, overlap.
Given the persistence of the pandemic in the U.S.—largely a result of a lack in widespread and timely diagnostic testing—a number of scientists are now advocating for the broad use of relatively inexpensive, rapid smell tests to help identify more of these quiet carriers of disease. The urgency, as students and workers look to recongregate indoors this fall, is clear. Some of the first attempts to reopen classrooms in Georgia, Mississippi, and Louisiana were followed by hundreds of students and staff being infected or else forced to quarantine.
“At this point, we need everything on the table,” Michael Osterholm, professor and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told The Daily Beast.
The Centers for Disease Control and Prevention (CDC) added the loss of smell or taste to its coronavirus screening guidelines back in April. So far, however, its integration into screening protocols has been limited to inclusion on self-report checklists. Yet studies suggest that not everyone with smell loss—especially if it’s subtle—even realizes they have it.
“The data are quite compelling that it is important for people to look out for smell loss as a potential early clue that they might have COVID,” Andrew Chan, a professor of medicine at Harvard Medical School and Massachusetts General Hospital, told The Daily Beast. “With additional research and development, smell tests certainly could be used as a screen for identifying people before they go into a workplace, school, or get on board an airplane.”
Smell loss is relatively specific to COVID-19, added Chan. So, as other viruses begin circulating more widely in the coming months, smell tests could prove particularly useful in discriminating cases of COVID-19 from the common cold or flu. “This could help reduce the number of people walking around with the virus without knowing it, and potentially spreading it,” he said.
Carthage plans to monitor all of its some 2,600 students daily for potential symptoms of COVID-19, with special attention paid to smell loss, according to Cameron. (The college is, like many other schools across the country, also pursuing a hybrid in-person and online education model that allows for social distancing.)
What does the test actually look like? At Carthage, the self-testing cards include eight scratch-and-sniff pads with questions. On one card, for example, a question asks if the odor smells like strawberry, garlic, leather, or gasoline. The eight correct answers are on the back of each card. Instructions note that a score of five or below denotes a potential smell problem. The effort will be run on the honor system with students asked to enter symptoms and test results daily into a smartphone app, explained Cameron. “The message to students is going to be that this is a public health initiative to help protect yourself and the people around you,” she said. “If you’re not honest about it, the negative consequences are clear.”
Carthage isn’t alone.
John Hayes, director of the Sensory Evaluation Center at Penn State University, said he got the green light a few days ago for university-wide random smell testing in conjunction with random nasal swab tests this fall. “With swab tests, even at their fastest turn-around times of 24 to 48 hours, a person that is positive can still go out and infect roommates and people in class. If we can identify them faster with a rapid smell test, we can cut a day or two off the transmission chain,” he told The Daily Beast.
“Given the choice between fever and smell,” he added, “I think smell is a better predictor.”
Kristina McAuliffe of Spokane, Washington, suggested the same based on her recent experience. She tested positive for COVID-19 in mid-July after noticing that she could not smell nor taste her ice cream—or anything, for that matter. “That was really my only clue,” McAuliffe, 42, told The Daily Beast. “It was a bizarre moment. I was opening up Vicks VapoRub, perfume, a jar of horseradish, just trying to get some moment of smell. But there was nothing.”
It was the same story for the two friends she had just visited in Idaho over the Fourth of July weekend. “Taking temperatures is moot,” she said. “None of us had a fever, or a cough.”
Such anecdotal stories, which date to early in the pandemic, are being increasingly backed up by scientific research. One preprint study that has not yet been peer-reviewed concluded that COVID-19 patients were about 27 times more likely to report losing their sense of smell, yet less than three times more likely to have fever or chills, compared to people without the virus.
“We found that smell preceded the onset of many other symptoms,” study co-author Andrew Badley, a professor of infectious diseases at the Mayo Clinic in Rochester, Minnesota, told The Daily Beast.
Of course, the presence of smell loss does not guarantee that a person has COVID-19. "People can lose their sense of smell for a variety of reasons,” Richard Doty, director of the Smell and Taste Center at the University of Pennsylvania Perelman School of Medicine, told The Daily Beast. “But if you have sudden smell loss in the middle of this pandemic, there’s a reasonable probability that you have been infected."
Chan cautioned the converse: People who can still smell should not be reassured that they are COVID-free, and should continue taking precautions such as physical distancing, wearing a mask, and washing their hands.
Doctors have used smell tests for decades. But these traditional tests can take upwards of 10 minutes to complete—which is less than ideal when passing a test is a condition, whether self-enforced or otherwise, for entering a closed space during day-to-day life.
“We want to craft a test with the minimal number of questions and minimal number of odors to make a reliable test,” Valentina Parma, a psychology professor at Temple University, told The Daily Beast. Other experts pointed to further considerations, such as creating multiple versions of a test so that people are less likely to cheat.
Some attempts have missed the mark. Earlier in the pandemic, authorities in Argentina required that people crossing borders between provinces sniff a Q-tip dipped in vinegar. When Ana R. Cofré, an otolaryngology specialist in Buenos Aires, learned of the testing, she determined that they could—and needed to—do better. She has since been part of a team validating a simple peel-and-smell test card—paired with a smartphone or computer app. So far, it has proven to be highly specific and sensitive to detecting COVID-19 in her country, she said.
“We’re planning to use it as a massive tool for screening,” Cofré told The Daily Beast through an interpreter. Beginning on Aug. 20, her team will begin testing thousands of people across urban and rural regions of Argentina. A positive smell test, she noted, will dictate who then needs the more expensive PCR nasal swab test that measures active infection.
A variety of other commercial smell tests are in development around the world. The U.S. National Institutes of Health issued an emergency call on Aug. 6 for research-funding proposals investigating “chemosensory testing as a COVID-19 screening tool.”
Danielle Reed, associate director of the Monell Chemical Senses Center in Philadelphia, just co-developed a test card with three small patches. The test involves choosing which patch has an odor, identifying that odor from a multiple-choice list, and then rating the odor’s intensity. An order of 20,000 of the tests is set to arrive in two weeks. Her team will then begin testing and collecting data, likely at local universities and hospitals, she said.
Meanwhile, Reed noted that she was monitoring her own sense of smell at home—sniffing her shampoo and her husband’s coffee every morning.
“If I got up one morning and couldn’t smell shampoo, then I’d get tested straight away,” she said. “New smell loss as a single symptom is probably among the best, if not the best, predictor of a positive COVID test.”
As the commercial smell tests get fine-tuned, and large-scale production begins, Doty predicts that many more institutions will likely look to implement them. Temple University and University of Florida are among other universities considering integration of the screening tool, school faculty told The Daily Beast. Mark Albers, a neurologist at Massachusetts General Hospital, who is currently leading a clinical study of smell test cards in Boston, noted that “some sports enterprises” had also expressed interest. Doty added that he has been contacted by a large automobile company looking to have its employees test their smell every day before they come into work, explaining he could not disclose the company name.
“People will come to their senses,” he said.