Loss of smell and taste possibly linked to COVID-19
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Review written by:
Tara Lucian, edited by Jingwen Zhang
There is mounting anecdotal evidence that anosmia (loss of smell) and ageusia (loss of taste) could be indicators of COVID-19, but it is unclear how prevalent these symptoms are or when they are likely to manifest. In South Korea, 30% of 2000 positive cases reported anosmia, which was sometimes the only symptom. A German report found that roughly half of patients had a smell or taste disorder as one of their symptoms, which usually developed after other symptoms. A German virologist who interviewed 100 patients with mild symptoms noted that two-thirds presented with anosmia. Otolaryngologists in various countries have reported seeing elevated rates of anosmia and ageusia among their patients.
Professional medical organizations have begun making recommendations based on this anecdotal evidence. The presidents of the British Rhinological Society and ENT UK recommended that healthcare providers use PPE when treating patients with anosmia or ageusia. British and American otolaryngologists have asked adults with anosmia or ageusia to self-quarantine for seven days. The American Academy of Otolaryngology has also requested that the CDC add anosmia as a symptom to COVID-19 screening tools. There is cause for concern for otolaryngologists as the specialty has experienced unusually high rates of transmission and deaths from COVID-19 in China, Italy, US and Iran.
Since other coronaviruses have been known to cause changes to smell and taste, the connection between those symptoms and COVID-19 is plausible. The World Health Organization is investigating the current evidence and has not yet ruled out that the reported anosmia and ageusia could be symptoms of allergies or a co-infection, such as a cold or flu. The exact mechanism for how COVID-19 could cause anosmia is not known, though experts have speculated that it could be due to inflammation in the nasal passages or to the virus attacking the nasal nerves directly. However, in most cases, smell and taste return within days or weeks.