Isosporiasis (also known as cystoisosporiasis) is an exclusively human parasitosis occurring mainly in the tropics and subtropics, due to infection with Isospora belli (through ingestion of contaminated food), that is frequently asymptomatic or that can cause fever and diarrhea, but that is usually a self-limiting condition in the immunocompetent. HIV-positive individuals are particularly at risk of suffering from symptomatic isosporiasis and can manifest with a more severe clinical course of chronic diarrhea and severe weight loss.