Cause of Lost Sense of Smell in COVID-19

Cause of Lost Sense of Smell in COVID-19

ARS-CoV-2 indirectly reduces the activity of olfactory receptors. Odor receptors consist of proteins on the surfaces of nerve cells in the nose that detect molecules associated with odors.

The new study, led by researchers from New York University Grossman School of Medicine and Columbia University, may shed light on the effects of COVID-19 on other types of brain cells, as well as other neurological effects that persist over a period of time, such as confusion, headaches and depression.


Experiments have shown that if the virus is found in the vicinity of nerve cells (neurons) in tissues related to the sense of smell, immune cells, microglia and T cells that sense and respond to the infection flock to the area. According to the study’s authors, such cells emit proteins called cytokines that alter the genetic activity of nerve cells involved in the sense of smell, even if the virus cannot infect them. According to the research team’s theory, the activity of immune cells is rapidly lost in other places, such as the brain, while the immune signals continue to reduce the activity of genes needed for the recovery of olfactory receptors.

“Our findings provide the first mechanistic explanation for the loss of sense of smell in COVID-19 and how this may underlie the long-standing biology of COVID-19,” said co-author Professor Benjamin tenOever, of the Department of Microbiology at NYU Langone Medical Center. The new study, in addition to another study by the tenOever group, shows how this epidemic virus, which infects less than 1% of the cells in the human body, can cause such serious damage to many organs.”

According to the researchers, one of the symptoms unique to COVID-19 is the loss of the sense of smell without the nasal congestion seen in other infections such as the common cold. Loss of the sense of smell lasts only a few weeks in most cases, while in more than 12 percent of COVID-19 patients it persists in the form of a continuing decrease in the ability to smell (hyposmia) or changes in the way a person perceives the same smell (parosmia).

Source: New York University Langone Medical Center/New York University Grossman Medicine

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