Covid-19: loss of smell must be taken seriously

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A study of European patients with mild or moderate forms of the coronavirus indicates that loss of smell is a recurring symptom that should alert. Women would be more affected by this clinical sign.

The first results of this research indicated, in mid-April, that loss of smell (anosmia) and loss of taste (ageusia), little observed in Asia, should be considered as potential symptoms of Covid-19 disease. On Wednesday, May 13, the final results of this research, published in the Journal of Intern Medicine, confirm that they are important signs of respiratory coronavirus infection. They are also recognized as such by the World Health Organization (WHO).

This epidemiological investigation was launched by the International Federation of ENT Societies. More than fifty ENT doctors and researchers, in eighteen European hospitals, analyzed the cases of 1,420 patients. Headache and loss of smell are the most common signs of Covid-19 in patients with a mild or moderate form of the infection.

Loss of smell, a "specific" symptom

Loss of smell is present in 70% of cases in observed patients. It is the first identified symptom, along with headaches. Contrary to the findings of the preliminary study, this would be "a specific symptom" of Covid-19. Loss of taste is not just the result of a stuffy nose or runny nose (runny nose).

"Covid-19's ability to invade the olfactory bulb, and therefore the central nervous system, is likely a clue to explaining anosmia, the researchers noted.

The other most common symptoms are headache (70.3%), stuffy nose (67.8%), cough (63.2%) and fatigue (63.3%), followed by muscle pain (62.5%), runny nose (60.1%) and loss of taste (54.2%). Fever was only reported by less than half of the patients (45.4%). Its average duration is 11 +/- 5 days.

In 65% of cases, smell disorders appear at the same time as general symptoms. But they can also occur before (12% of cases) or after (23% of cases).

Chinese publications reported only 5% of smell and taste disorders. The researchers believe that successive genetic mutations of the coronavirus specific to European populations could explain this difference. In fact, European populations have a higher level of angiotensin-converting enzyme 2 (ACE2) in the anal mucosa, which acts as a receptor for the coronavirus.

Coronavirus symptoms differ according to age and sex.

Researchers have confirmed that the prevalence of symptoms varies by age and gender. Young patients most often have ear, nose, and throat disorders, while older patients often have fever, fatigue, and loss of appetite. Also, loss of smell, headache, nasal blockage, and fatigue are more common in women. Men suffer more from cough and fever.

"It appears that women, compared to men, are less likely to have complications from viral infections based on different innate immunities, steroid hormones, and X chromosome factors," the study said. Immune regulatory genes encoded by the female X chromosome can cause lower levels of viral load and therefore less inflammation compared to male patients.

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