HIV/AIDS Glossary

A single-celled microorganism. Some protozoans can cause disease in humans, including Toxoplasma gondii (causes toxoplasmosis), the group Plasmodium (causes malaria), and the group Cryptosporidium (causes cryptosporidiosis). People with weakened immune systems, including people with HIV, are at a higher risk for protozoan infections than people with healthy immune systems.