What Causes Long COVID?

First, we need clarify what is meant by Long COVID.  The definition of long COVID is being perfected but for now, it refers to new mental or physical symptoms that are present four or more weeks after your acute COVID infection.  We know the SARS-CoV-2 virus causes COVID-19 and we are getting better understanding about why infection with SARS-CoV-2 creates so much lung damage.  How this virus causes the symptoms of Long COVID in other body systems is still being worked out but, we have some clues.

Yep!  Hamsters get COVID-19 and they suffer the same complications as human, including LONG COVID!

This means they can be studied for clues to how COVID-19 induces Long COVID in humans.

The first symptom of long COVID explored in hamsters was loss of smell.  Hamsters loose their sense of smell with COVID-19 just like humans and this effect can be long lasting.  The study describing these observations performed by Zazhytska et al. was published in the journal Cell.

In hamsters that suffered lasting loss of smell, evaluation of the olfactory nerve showed damage to a particular structural cell in the olfactory (smell) bulb connected to the nose.  The damage to these cells results in a large amount of inflammation which impairs the normal functions of olfactory nerve cells in the same tissue.  The nerve cells are not damaged but cannot maintain their normal smell-functions resulting in loss of the sense of smell.

The normal immune response eventually gets control of this inflammation, allowing the olfactory nerve cells to resume their normal smell-related functions and the sense of smell returns.

The same inflammation-related malfunction was found in other areas of the hamster brain.   If true in humans, this may explain neurological and mental changes that have been reported in Long COVID.

Fixing it.

Studies are currently looking to see if shutting down the inflammation response with medication will allow more rapid recovery of these neurological functions including smell and other mental health functions.

Until we have a more detailed understanding of the cause of lasting changes in the brain and other body systems in Long COVID, we will focus on assisting patients with a wide variety of symptoms. Our overall goal is to improve functional capacity and quality of life in these patients.