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Sixty seconds on . . . anosmia

BMJ 2020; 368 doi: https://doi.org/10.1136/bmj.m1202 (Published 24 March 2020) Cite this as: BMJ 2020;368:m1202

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  1. Gareth Iacobucci
  1. The BMJ

I’ve read about this. What’s the link?

While a high temperature and a new, continuous cough are the most established symptoms of covid-19, the World Health Organization is now examining how common it might be for infected people to experience a loss of smell (anosmia) or taste (ageusia).

Is this common with this type of virus?

A lot of respiratory viruses can cause problems with smell receptors. And there is evidence that previous coronaviruses have been associated with post-viral smell loss. In a joint briefing paper,1 British Rhinological Society president Claire Hopkins and Nirmal Kumar, president of ENT UK, said that previous coronaviruses are thought to account for 10- 15% cases of anosmia.

What about covid-19?

There are emerging reports that people with covid-19 have experienced such symptoms. For those with a nose for stats, the UK experts note that in South Korea, where testing for covid-19 has been extensive, 30% of patients testing positive have had anosmia as their major presenting symptom in otherwise mild cases.

What is WHO saying?

On 23 March it said that it was looking at covid-19 cases that have already been reported to see if the symptoms are a common feature. But it has stressed that the evidence of a connection between anosmia and covid-19 is not yet there.

What do researchers need to establish?

How common the link is, and at what stage of infection patients are losing their sense of smell. Experts also need to sniff out whether the symptoms are an indication of covid-19 or of allergies, colds, or seasonal flu, which can all cause anosmia or ageusia.

Are the symptoms temporary?

Currently, smell loss in patients with covid-19 appears to be lasting for only a short period of time. But we won’t know how many cases lead to more long lasting problems.

So, should people with these symptoms be self-isolating?

WHO hasn’t added anosmia to its covid-19 symptom list.2 But UK experts smell an opportunity to act. If adults with loss of smell but no other symptoms self-isolate for seven days alongside people with more established symptoms we “might be able to reduce the number of otherwise asymptomatic people who continue to act as vectors,” they argue.1

References

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