Hi.
In the fwiw department, some people are genetically more predisposed than others for certain diseases. One example is sickle cell anemia. There are many others (Sars covid 2 etc regarding the elderly and co morbidity).
It’s possible, look up Ft. Detrick MD.
5.56mm
USAMRIID.
I read “The Hot Zone” quite a few years ago, and it was quite the eye-opener and riveting.