New research led by scientists at Harvard University Medical School explains one of the many mysteries of COVID-19: why people infected with the virus temporarily lose their sense of smell.
The loss of smell has been the most common neurological symptom of the virus. The study's lead author, Dr. Sandeep Robert Datta, said their findings about why that happens was a surprise and could lead towards eventual treatments for a range of neurological disorders caused by the virus.
Harvard neuroscientists took a close look at a specialized type of sensory neurons in the nose that detect and transmit smells to the brain.
"Our intuition, and I think the intuition of many other people, would be that the virus would attack these sensory neurons and damage or kill these neurons, and that's how we lose our sense of smell," said Datta, an associate professor of neurobiology in the Blavatnik Institute at Harvard Medical School. The study Datta led was published Friday in the journal Science Advances.
"But in looking at our data, we got a big surprise," he said. "Which is that it seems like the virus is not actually capable of attacking the neurons that live in your nose."
Instead, the scientists discovered that two other kinds of cells that support those neurons are being attacked. Those cells can regenerate more quickly.
"And so we think, on the whole, this is good news, and suggests that people who lose their sense of smell, for the most part, are going to go on to get their sense of smell back," Datta said.
That's what doctors have seen as the epidemic has progressed — most patients regain their sense of smell in several weeks.
"We finally have clues that lead us to understand how it is the virus might attack your sense of smell," Datta said, "which leads us to theories about how it might attack your neurological systems more generally."
In addition to a loss of smell, the virus has caused a number of other neurological symptoms, including altered consciousness, difficulty concentrating, sensory motor deficits, and strokes. Datta said he's hopeful that this new understanding of what cells the virus attacks in the nose might prove useful in understanding those other symptoms.