Among many mysteries of the COVID-19 pandemic, loss of smell is one with estimated tens of millions of people having lingering problems with their sense of smell and so far, no clues on what causes this. Scientists are gradually understanding how the SARS-CoV-2 coronavirus causes loss of smell and several trials are undergoing for potential treatments to tackle the condition.
A study involving 616,318 people in the US who have had COVID-19 showed that the rate of chemosensory disruption is falling with every major variant of concern (Original Alpha variant: 50%, Delta variant: 44%, and the latest Omicron variant: 17%).
Although it is gradually declining, another study reported that even after one year of infection, 46% of those who had had COVID-19 still had smell problems compared to only 10% in the control group. In general, SARS-CoV-2 seems to cause damage to the olfactory neurons in the nose, scrambling their nuclei, while few people also seem to be genetically predisposed to smell or taste loss.
While these emerging data are supporting the development of potential treatments, as of now the only thing that most researchers are recommending is smell training - practicing with samples of strong-smelling substances to restore olfactory signaling.