How the Coronavirus Steals the Sense of Smell

Anosmia, the abrupt loss of smell that has become a well-known hallmark of the disease, is one of the many peculiarities of Covid-19. Even without a nose, covid patients lose their sense of smell and taste, which can make food taste like cardboard and coffee smell bad.

The mechanisms that allow the coronaviruses to enter cells have been a mystery, prompting a long debate about whether they can be infections at all.

Insights gleaned from new research could shed new light on how the coronavirus might affect other types of brain cells, leading to conditions like brain fog, and possibly help explain the biological mechanisms behind long Covid symptoms that linger.

The new work settles the debate over whether the coronaviruses cause any harm to the nerve cells that detect odors. The researchers found that the virus attacks other supporting cells.

The immune cells flood the region to fight the virus. The inflammation wreaks havoc on smell receptors, the cells in the nose that detect and transmit odors.

The process short-circuits the genes in those neurons.

Dr. Datta, who was not involved in the study, said that the paper greatly advances the understanding of how cells critical to the sense of smell are affected by the virus.

There are a lot of bad things that happen if you affect the support cells in the nose.

The immune system's friendly fire as it responds to infections can cause many of the problems of Covid.

A lot of what the virus is doing to us is a consequence of its ability to generate inflammation, according to Dr. Datta.

The research was done at the Zuckerman Institute and Irving Medical Center at Columbia University in New York, the New York University Grossman School of Medicine, the Icahn School of Medicine at Mount Sinai in New York, and the School of Medicine in Houston. The research was published in February.

The golden hamsters and human tissue were examined by the scientists. Scientists tracked the damage to the hamsters' olfactory systems after they were exposed to the original coronaviruses.

How do you know if a golden hamster has lost its smell? Benjamin tenOever, a professor of microbiology at NYU Langone Health and an author of the new research, said that you don't feed it for several hours and then bury Cocoa Puffs in its bedding. Hamsters that can smell food will find it.

The cells that play supporting roles in the olfactory system were the only ones that were invaded by the virus. A loss of smell was caused by the change in function of the nearby neurons.

The immune response altered the architecture of genes in the neurons, disrupting production of odor receptors, said Marianna Zazhytska, a graduate student and one of the paper's first authors.

The system inflammatory response is what is causing all this reorganization.

The ability to send and receive messages is disrupted. The system can recover after the illness is over.

One of the paper's authors said that earlier work at the Zuckerman Institute showed that odor detecting neurons have complex organizational structures that are essential to the creation of odor receptors.

The organization of the neurons is completely different when they are bitten, according to Dr. Lomvardas.

There is a signal released from the cells that receive the odors that tells them to reorganize and stop expression of the olfactory genes.

He suggested that this may be an evolutionary adaptation that offers a form of antiviral resistance and that its main purpose is to prevent the virus from entering the brain.