COVID-19 patients’ loss of smell likely is temporary

Scientists have figured out how COVID-19 causes many people to lose their sense of smell. And they have good news: The loss appears to be temporary because the actual cells in the nose that detect smell aren’t harmed.

Temporary loss of smell is called anosmia by doctors. It’s one of the earliest and most commonly reported indicators of COVID-19. In fact, studies suggest it’s a better predictor of infection with the disease than fever and cough.

But exactly why people with COVID-19 stop being able to smell was unclear. It was thought damage or inflammation of the olfactory sensory neurons that detect and transmit the sense of smell to the brain caused the problem.

That turned out to be wrong.

In a paper published Friday, researchers found that SARS-CoV-2, the virus that causes COVID-19, instead attacks the cells that support those smell-detecting neurons but not the neurons themselves.

“The novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of supporting cells,” said Sandeep Robert Datta, a professor of neurobiology at Harvard Medical School and a co-author on the paper published in the journal in Science Advances.

That’s good news because it means the infection isn’t likely to permanently damage COVID-19 patients’ olfactory neural circuits.

“Once the infection clears, olfactory neurons don’t appear to need to be replaced or rebuilt from scratch,” he said. “But we need more data and a better understanding of the underlying mechanisms to confirm this conclusion.”

COVID-19 patients typically recover their sense of smell over the course of several weeks.

In other viral infections that damage the olfactory neurons patients can take months to regain their sense of smell.

Scientists say patients are likely to regain their lost of a sense of smell over several weeks. GETTY