An Israeli scientist is urging people to ask a simple question daily to save lives from coronavirus: can I smell?

There is widespread confusion about how to identify coronavirus symptoms, as several of them are similar to symptoms of flu and the common cold. But Noam Sobel says that there is one highly unusual pattern, a sudden inability to smell, and he has built a website to help people keep tabs on their odor-assessing abilities.

People are signing up from all over the world, at an average rate of 200 per hour.

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“The pattern that seems to be emerging is people start to feel malaise, and then even as soon as the next day have an almost total loss of the sense of smell,” said Sobel, a professor at the Weizmann Institute of Science’s Department of Neurobiology. “Yes, the same is true with the cold and flu, but not to the same extent.”

Sobel, a specialist in the potential of smell to improve understanding of medical conditions and head of a 20-person lab dedicated to this, didn’t realize that smell could be so relevant in detecting coronavirus until a colleague contracted the disease.

“The general population talks about smell in an imprecise way,” he said. “But when my colleague lost his sense of smell, and was able to quantify the loss in terms we use in our lab, we knew that this could be used to contribute to diagnosis,” he said.

Sobel and his team have already translated this observation in to an online tool which they say will help people tell if they may have coronavirus. They built smelltracker.org, a website available in six languages, where users sign up and select five items they have in stock at home, and are happy to smell daily. Choices include honey, peanut butter, vinegar, freshly chopped garlic, and toothpaste.

They receive a reminder to sniff each item each day, and adjust on-screen sliders to rate its strength and pleasantness. If their sensitivity to an odor changes significantly, the site displays a red screen telling them that their smell is blunted. “This then becomes good information for people to share with their physician,” said Sobel.

He has also been pioneering a technology that could help people who are diagnosed with coronavirus, and hospitalized. Doctors have become worried by the sudden deterioration of some patients who appeared to be in a stable condition.

“A small fraction of them will suddenly deteriorate,” said Sobel. “They will be okay and then, boom, you will have rapid deterioration, and it would be very very helpful if that could be detected earlier.”

His team has adapted sensors that they have been using for their research, to monitor airflow from the nose, so that they can monitor changes in patients’ airflow, which can signal they are headed to a danger zone from coronavirus symptoms.

“For our research we’ve developed sensitive tools to measure nasal airflow, and we’ve developed a tiny wearable that weighs six grams and transmits data via bluetooth,” said Sobel.

The wearable sensor is ready for use by coronavirus patients, awaiting regulatory approval, and Sobel is optimistic about its potential. He said: “The goal is to try to catch those people, one day earlier, who really fall apart — this can be a matter of life and death.”