yep, the O's. if youre into rabbit holes, look into the A-, B-, AB-, and O- groups and how theyre different from the positives. theres a theory that they evolved separately from the other group in various ways, etc.
I'm O neg. so i think i had covid during the entire month of december but i was never approved for a test because i never had a fever, never lost my taste, and my symptoms werent really bad with the most popular red flags. i just had alot of mucous going on. and it seemed to last forever. i think i just got my voice back to normal.
expanding on this topic for the O's ..specifically RH negative O's, some of them are resistant to HIV as well due to mutations in their CD4 cells (which the HIV virus uses to hijack and replicate)
these are just some things ive come across, for the sake of entertainment. take with a grain of salt.