Scientists have figured out how COVID-19 causes many people to lose their sense of smell. And they have good news: The loss of their smell appears to be temporary because the actual cells in the nose that recognize 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 can better predict whether someone likely suffers from the disease than fever and cough.
But to be exact, why people with COVID-19 stop being able to smell was unclear. It was thought that damage or inflammation (炎症) of the sensory nerve cells that detect and send the sense of smell to the brain caused the problem. That turned out to be wrong.
In a paper published on Friday, researchers found that SARS-CoV-2, the virus that causes COVID-19, attacks the cells that support those smell-detecting neurons (神经元) but not the neurons themselves.
"The novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of those supporting cells," said Sandeep Robert Datta, a professor at Harvard Medical School.
That's good news because it means the infection isn't likely to permanently damage COVID-19 patients' smell nerves. "Once the infection disappears, smell 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 hidden theory to confirm this conclusion."
COVID-19 patients typically recover their sense of smell over the course of several weeks. In other infections caused by a virus patients can take months to regain their sense of smell.
