CHICAGO (WBBM NEWSRADIO) -- Loss of smell or anosmia can be a first sign of COVID-19 and/or linger well after the infection is gone.
There’s been an explosion in the number of people who have been experiencing this symptom and WBBM Newsradio’s Nancy Harty talked with a local researcher about why.
It's a common symptom of COVID and in some mild cases the only one: anosmia, or loss of smell. It can range from disorienting to debilitation, and even lead to depression.
Assistant Professor of Neurology at Northwestern University Christina Zelano explained how researchers believe COVID could lead to smell loss.
"Not by directly infecting neurons, but my infecting the support cells that are located right next to the neurons inside of the nasal cavity," she said.
Dr. Zelano said while most people regain their smell in weeks, others don't.
"Some people, maybe one in 20, experience the same loss of smell that lasts more than six months. We don't really know yet if that's permanent," she said.
She offered a theory on why it takes so long.
"If inflammation from the virus is severe, the damage could spread, potentially including the olfactory neurons; and in those cases, recovery of smell would be much slower, because the olfactory neurons need time to regenerate," she said.
After anosmia, she said some COVID sufferers experience parosmia, when normally pleasant odors smell distorted or bad.
"About half of the people who lose their sense of smell from a viral infection, may experience it as they recover. And the altered sense of smell is usually temporary," Dr. Zelano.
While having your coffee or chicken smell rancid, she said it is a sign your smell is returning and that new neurons are growing.
Dr. Zelano said smell training has shown to help people recover and ever retrain their brains.