Covid caused loss of smell (and sore throat)
occurs much earlier than elevated temperature

https://medicalxpress.com/news/2020-10-loss-earlier-covid-symptom-fevera.html

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A new analysis of coronavirus studies that involved Monell found that 77% of coronavirus patients had complete or partial loss of smell when tested. Forty-four percent were aware of the symptom without testing. Loss of sense of smell (along with sore throat) is also one of the earliest symptoms, making it more useful than later symptoms for protecting others from exposure, Rawson said.

"It is one of the earliest symptoms, and it is certainly earlier than fever," she said. "Smell loss alone predicts diagnosis better than a fever." Taste loss can occur as well, but it is less common and often related to smell loss.

Rawson's interest in what coronavirus does to the sense of smell—aka olfaction—goes well beyond its potential for screening. The pandemic, she said, could leave up to 750,000 Americans unable to smell, and that has major implications for their safety and quality of life.

She has been testing her own sense of smell each evening this month. She's participating in a pilot study of a new screening system that she hopes will lead to a large clinical trial. But the tests also ease her mind about allergy symptoms. She said a number of studies evaluating smell tests for coronavirus screening are in the works.

The trial Monell hopes will receive funding involves a smell test it developed called Scentinel.
The Philadelphia nonprofit partnered with Scentisphere to create the test,
which contains three peel-and-sniff films. Two have no scent. The third contains a rotating group of familiar odors like coffee, chocolate, popcorn, and natural gas. People who take the tests are asked to say which strip (if any) has a scent, rate its intensity, and identify the odor.

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