The COVID-19 symptom of odor loss, like anosmia, is unusual in that it differs from that of the common cold like flu.
With these diseases, a blocked nose is usually the culprit, caused by inflammatory swelling of the area. For some people who have COVID-19, however, anosmia is their only symptom – but it is ‘much deeper’ than with regular flu.
The reason for this could lie in the mechanism by which the virus infects our cells, new research suggests.
Read the latest news about coronavirus:
The ‘entry point’ for SARS-CoV-2, the virus that causes COVID-19, is thought to be a protein found on the surface of some human cells. These are cells found in the heart, lungs, intestines, throat and nose.
The protein, a type of enzyme called the ‘angiotensin converting enzyme II’ (ACE-2), has a specific form designed for its function – to take the hormone angiotensin, and convert it into angiotensin II, which is used around the body for things like regulating blood pressure. While the form of ACE-2 fits nicely with angiotensin, it also binds to the prickly outer proteins of the coronavirus.
By looking at tissue samples from patients’ noses, a team of scientists from the John Hopkins University School of Medicine hopes to quantify how many ACE-2 proteins were found on each type of cell. They found that the levels of the protein on the olfactory epithelium, the tissue at the back of the nose used to detect odor, were ‘remarkably’ high, between 200 and 700 times higher than in other areas of the nose. noas.
It is thought that this finding could indicate potential avenues for the treatment of the infection directly through the nose.
“These olfactory support cells are needed to protect and maintain the delicate neurons in the nose that detect odors and signal that information to the brain,” said study author Dr. Andrew P Lane.
“In general, when cells are infected with a virus, they undergo a process called pyroptosis – and essentially hit the self-destruct button to fill the virus. That, most likely, oil factor-supporting cells destroy themselves, which in turn leads to the death of sensory neurons and loss of the sense of smell. “
Read more about the symptoms of COVID-19:
Further studies looking at recovery of COVID-19 patients have found that these neurons return over time, although the long-term effects are not yet known.
“Some COVID-19 patients report disturbed odor – parosmia – that persists months after their smoke return,” Lane said. “This long-lasting odor disorder with COVID-19 is unusual and warrants further study.
“It is possible that this changed odor function may be permanent, but it is too soon to know. We are optimistic that this will eventually disappear when the brain ‘learns’ to interpret signals from the regenerated olfactory feed.’
What is viral load and why is it important for coronavirus?
Viral load is just the amount of virus in the body. This varies in different parts of the body, and can change over time. Recent studies, for example, have shown that the viral load in the lungs of COVID-19 patients is greater than that in the nose.
A patient’s viral load increases as the virus recurs and disease symptoms diminish, and then decreases as the patient recovers. That checking the viral load can give us a useful indication on how a patient’s infection is progressing.
The amount of virus you are exposed to at the onset of an infection is something else, and this is called the ‘infected dose’. Studies on other viruses such as influenza and SARS have shown that the higher the infected dose (the more virus you inhale), the greater your chances for more severe symptoms.
With one small exposure, your immune system can fight the virus before you get sick, but with repeated small exposures (like touching your face all day) or one large exposure (an infected person coughing in your face), it virus can grow faster than your body can manage.
We do not yet know if this link between infected dose and disease severity applies to COVID-19, but it can, and that’s why it’s so important to maintain physical distance and keep the initial exposure as low as possible.
Read more:
