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The One Sure Sign Someone Has Caught COVID

Coronavirus has many symptoms, but one is more common and unique than others.
Woman Trying to Sense Smell of a Lemon

COVID-19 has an infamously long list of symptoms, from a dry cough to a rash on the toes. That may prevent some people from getting an expedient diagnosis, as many physical signs may be confused for other issues, such as allergies or the common cold.

However, one symptom is both common and relatively unique to the coronavirus—a fairly sure sign that you've caught COVID: The loss of smell or taste. It's usually the one sure sign someone has COVID. Read on to find out how to spot it, and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had Coronavirus.

COVID seems to attack nose first

A recent analysis of studies found that 77% of coronavirus patients reported a loss of smell when they were tested and that it was one of the earliest symptoms of the disease. Another study has found that loss of smell was a more reliable indicator of COVID-19 than better-known symptoms such as fever and cough.

Meanwhile, a loss of taste or smell is rarely associated with other conditions whose symptoms overlap with COVID-19, such as colds and allergies.

Scientists aren't exactly sure why the coronavirus tends to cause anosmia (the scientific term for loss of smell), but the picture is becoming clearer.

"We have been researching this data for less than a year. Still, so far, it suggests that the primary attack of the coronavirus is in the nose, in the nasal epithelium, which is the skinlike layer of cells in charge of expressing odors," says Leo Nissola, MD. "It seems like the virus assaults support cells and stem cells in the nose, but not neurons directly, which does not mean that neurons cannot be affected."

He adds: "These cells maintain the balance and signal the brain. In some patients, when infected with COVID, that balance is disrupted, and that leads to a shutdown of neuronal signaling, and therefore of smell. The cells also provide support to sustain the cilia on the nose where receptors that detect odors are located. If the virus disrupts those cilia, you lose the ability to smell."

RELATED: COVID Symptoms Usually Appear in This Order, Study Finds

"Smell blindness" is common, can be chronic

Several studies have found that the loss of smell is a common—and potentially long-lasting—COVID symptom. According to one survey published in the Journal of the American Medical Association earlier this year, 64% of coronavirus patients reported a loss of smell or taste. A July CDC study found that symptom lasts for an average of eight days, but some people experience it for weeks. 

That can be problematic, as "smell blindness" can lead to a loss of appetite and malnutrition. 

As for yourself, do everything you can to prevent getting—and spreading—COVID-19 in the first place: Wear a face mask, get tested if you think you have coronavirus, avoid crowds (and bars, and house parties), practice social distancing, only run essential errands, wash your hands regularly, disinfect frequently touched surfaces, and to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.