'Sadly, my colleagues and I were to become far more familiar with life-threatening parasitic infections. In the early years of the aids epidemic, I lost many of my patients to them. An aids patient’s devastated immune system might allow the parasite Toxoplasma gondii, carried by cats, to form brain abscesses; Cryptosporidium infection, which normally infests cattle, caused wasting from relentless diarrhea.'

https://www.newyorker.com/magazine/2022/12/12/in-praise-of-parasites