Health authorities in France have said in recent days that they are observing a possible new symptom of Covid-19 - the loss of a sense of smell (known as anosmia).
The head of the French health service, Jerome Salomon, has said "the sudden disappearance of smell" in patients who did not have a blocked or runny nose appeared to be a symptom, albeit a rare one.
He said a loss of taste was an even rarer symptom and that both seemed to be more prevalent in young people with the virus.
ENT UK, which represents ear, nose and throat specialists in the UK, has suggested that anosmia be added to the current symptom criteria for people to self-isolate.
"There has been a rapidly growing number of reports of a significant increase in patients with Covid-19 infection presenting with loss of smell in the absence of other symptoms," it said in a statement with the British Rhinological Society.
Other doctors have cautioned that the research is not yet developed enough.
Valérie Barrault, a 59-year-old Covid-19 patient in the Paris area experiencing anosmia, told the BBC: "You eat and you can't taste anything... This is stressing me right now."