Loss of smell: A potential early symptom of Covid-19

Can’t smell the flowers? It might be an early sign that you are infected with the coronavirus that causes Covid-19. — Reuters

A loss of smell or taste might be an early sign of infection with the SARS-CoV-2 virus that causes Covid-19, say medical experts who cite reports from several countries.

It might even serve as a useful screening tool, they say.

The idea of a virus infection reducing sense of smell is not new.

Respiratory viral infection is a common cause of loss of smell, because inflammation can interfere with airflow and the ability to detect odours.

The sense of smell usually returns when the infection resolves, but in a small percentage of cases, smell loss can persist after other symptoms disappear.

In some cases, it is permanent.

Now there’s “good evidence” from South Korea, China and Italy for loss or impairment of smell in infected people, says a joint statement from the presidents of the British Rhinological Society and of ENT UK, a British group that represents ear, nose and throat doctors.

In South Korea, some 30% of people who tested positive for the virus have cited loss of smell as their major complaint in otherwise mild cases, they wrote.

So that might be a useful way to spot infected people without other symptoms like fever, coughing and shortness of breath, they wrote.

A similar proposal was published on March 22 (2020) by the American Academy of Otolaryngology-Head and Neck Surgery.

It noted “rapidly accumulating” anecdotal evidence from around the world that the coronavirus can cause not only loss of smell, but also a diminished sense of taste.

So the appearance of those symptoms in people without another explanation should alert doctors to the possibility of a Covid-19 infection, the group said.

World Health Organization (WHO) outbreak expert Maria Van Kerkhove said that the United Nations health agency is looking into the question of whether the loss of smell or taste are a defining feature of the disease.

Dr Eric Holbrook, a nasal and sinus disease expert at the Massachusetts Eye and Ear hospital in Boston, United States, said the reports have been a hot topic among researchers and doctors.

But “we don’t have hard evidence right now” about how often smell loss occurs in people infected with the coronavirus, he said.

Dr Holbrook said the reports he has seen suggest the sense of smell returns within a couple of weeks, but how long it lasts has yet to be firmly established.

He also said it’s difficult to assess reports of a loss of taste because people with an impaired sense of smell often report a loss of flavour, which is technically different from an impairment in taste.

Dr Holbrook said he is trying to set up a study of smell in people being tested for the coronavirus at Boston hospitals. – AP