By now, everyone probably knows someone who has or had Corona. In the last 24 hours, more than 34,000 new infections were counted again. The currently rampant Omicron variant BA.2 is characterized by high infectivity but comparatively with mild course of the disease. This can lead to re-infection within a short time after overcoming an infection. How is this possible?
“The problem lies in the mucosal surface,” says the expert. The coronavirus enters the body via the respiratory tract, i.e., the nose or mouth, and attaches itself to the mucosal surface. Only a part of all the antibodies circulating in the body is located. The rest is in the blood. This means that you do not have your entire antibody potpourri 1:1 on the mucous membrane of your nose or mouth.
What follows is clear: “If I breathe in more virus particles than I have on the antibodies on the mucous membrane, I get infected. Simply because the body has too few neutralizing antibodies on the mucous membrane to be able to fight all the virus particles.” Because of this, a virus particle usually does manage to infect the mucosal cell, setting the infection. “The antibodies in the bloodstream protect my lungs and prevent this infection, which is local to the nasopharynx, from migrating to the lungs and causing more severe damage. This protects against hospitalization and severe courses, but we are not protected against symptomatic infection,” says expert virologist Monika Redlberger-Fritz.
This is also why omicron can still take a severe course in the unvaccinated. “If I don’t have antibodies in my bloodstream due to the vaccination, bronchitis, and pneumonia can still happen,” the expert warns.
“Protection against a severe course of the disease makes vaccination so important. Because whether it’s SARS-CoV-2, influenza, whooping cough or rotavirus, the quantity problem of mucosal antibodies is what allows viruses to infect – in children and adults.”
The only way to protect against infection is to intercept the particles with a barrier at entry – like a mask. “It prevents us from inhaling large amounts of the virus, which would outsmart our mucosal antibodies. The few particles that get through are easily caught by the antibodies and prevent infection,” says the virologist.
Shortly after an infection, which may still be highly symptomatic, the high antibody level on the mucous membrane prevents an immediate re-infection for a while. However, this antibody level soon drops. How quickly it falls cannot be said in general terms but depends on the individual and several factors. “Therefore, there is no ‘carte blanch that guarantees to be immune for period X.” Thus, the risk of re-infection increases with time. “Statistically, you are considered re-infected after three months – but again, this cannot be applied across the board to all people.”
- source: heute.at/picture: pixabay.com
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