The more I think about it, the more I think Covid is either strongly associated with parasites or is a parasite.
I grew up on a farm and it's long been known that feeding your livestock tobacco rids intestinal parasites.
I don't smoke but, If you'll remember earlier this year how cigarette smoking was shown to correlate with less Covid infections.
Ivermectin an anti-parasitic helps with Covid too.
Here's some research on tobacco.
https://pubmed.ncbi.nlm.nih.gov/31276744/