https://www.cbc.ca/radio/quirks/beyond-long-covid-1.7485888

"There is no such thing as a COVID infection without consequence," says long COVID researcher, David Putrino[…].

So there is a cumulative effect that can be occurring with each infection.

Early in the pandemic, we actually published a paper where we showed that, even in animal models — when we infected mice with a very, very mild case of SARS-CoV-2 infection — which only caused lung inflammation, we still saw these inflammatory chemicals called chemokines emerging from the infected lungs and starting to attack central nervous system structures such as the spinal cord and the brain.

[…]You know, this is a virus that, once it enters the body, is very capable of entering the bloodstream, creating immune responses that travel all over the body.

It disrupts what we call "interferon signalling," which is part of the immune system that helps you to fight off infections or latent infections, such as Epstein Barr virus.

Typically our immune system can keep these things suppressed, but when SARS-CoV-2 enters the picture, it starts to cause altered interferon signalling. It causes immune damage and dysregulation.

And suddenly, not only does your body have trouble clearing the SARS-CoV-2 virus itself, but it also starts to have trouble keeping some of these other viruses that have been latent from reactivating and causing problems.

In addition to SARS-CoV-2's ability to dysregulate the immune system and suppress the immune system, the spike protein itself is very damaging to blood vessel structures as well as red blood cells and platelets themselves.

And so between those two features, the ability to dysregulate the immune system and the ability to cause systemic damage throughout the bloodstream, you have a very dangerous novel virus on your hands.