May 22, 2022

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Why does the sense of smell and taste fail after COVID-19 infection?

Why does the sense of smell and taste fail after COVID-19 infection?



 

Why does the sense of smell and taste fail after COVID-19 infection?

Nature sub-issue: One of the biggest mysteries of the COVID-19 has been solved. Why does the sense of smell and taste fail after infection with the COVID-19?

 

Loss of smell, or loss of taste , is a unique symptom after COVID-19 infection and one of the earliest and most frequently reported symptoms in the acute phase of infection.

Unlike other viral infections, the loss of smell or taste occurs suddenly after Covid-19, and there is no obstruction of the nasal mucosa.

 

Although a large proportion of people infected with COVID-19s will experience loss of smell or taste, a considerable proportion of infected people will not experience these two symptoms, and the underlying mechanisms are still unclear.

 

On January 17, 2022, the research team of 23andMe in the United States published a research paper entitled: The UGT2A1/UGT2A2 locus is associated with COVID-19-related loss of smell or taste in Nature Genetics , a sub-journal of Nature .

 

The study sheds light on genetic risk factors that predispose individuals to developing symptoms of loss of taste or smell after infection with COVID-19 . This locus (located near the genes UGT2A1 and UGT2A2) was associated with an 11% increased chance of developing either symptom after infection with the new coronavirus.

 

Why does the sense of smell and taste fail after COVID-19 infection?

 

For the study, the research team collected self-reported data from more than 1 million 23andMe study participants.

Of those, 69,841 people over the age of 18 who tested positive for Covid-19 reported their own symptoms of Covid-19.

Loss of smell or taste occurred in 68% of them, and the probability of occurrence in women was higher than that in men (72% in women and 61% in men) , and the probability of occurrence in young people was higher .

The average age of people with loss of sense of smell or taste was 41 years old.

The average age of those without the symptoms was 45. In addition, East Asian and intangible cultural heritage Americans have a significantly lower risk of loss of smell or taste after contracting the COVID-19 than Europeans and Americans.

 

Comparing the symptoms of COVID-19 with those of a cold or flu-like illness, loss of smell or taste is the most striking difference.

 

Why does the sense of smell and taste fail after COVID-19 infection?Symptoms of COVID-19 compared to other cold or flu-like illnesses

 

The team then conducted a genome-wide association study (GWAS) of it and compared it with those who had contracted Covid-19 but did not experience loss of smell or taste.

 

The research team identified an important single nucleotide polymorphism site near the UGT2A1 and UGT2A2 genes on chromosome 4 -rs7688383.

The mutation of this site C to T causes individuals to lose their sense of smell or taste after infection with the new coronavirus. Likelihood rose by 11% .

 

Why does the sense of smell and taste fail after COVID-19 infection? Why does the sense of smell and taste fail after COVID-19 infection?

 

UGT2A2 is a shorter transcript of UGT2A1, and both genes are expressed in the olfactory epithelium within the nose and play a role in odor metabolism.

The enzymes they produce are involved in eliminating odorant molecules that bind to receptors involved in olfactory detection .

 

The finding sheds light on the biological mechanisms behind COVID-19-related loss of smell or taste .

However, the research team also said that although the sample size of the study was large, the findings may be biased towards individuals with European ancestry.

And there was no loss of smell and taste in the study, which were combined into one symptom when patients reported voluntarily.

 

 

Paper link :
https://nature.com/articles/s41588-021-00986-w

Why does the sense of smell and taste fail after COVID-19 infection?

(source:internet, reference only)


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