Toxoplasma gondii is an intracellular parasite that causes the infectious disease toxoplasmosis.
Found worldwide, T. gondii is capable of infecting virtually all warm-blooded animals.
In humans, T. gondii is one of the most common parasites in developed countries; serological studies estimate that 30–50% of the global population has been exposed to and may be chronically infected with T. gondii, although infection rates differ significantly from country to country.
Infection with T. gondii usually produces no readily observable symptoms in healthy human adults. Occasionally, people may have a few weeks or months of mild, flu-like illness such as muscle aches and tender lymph nodes. In infants, HIV/AIDS patients, and others with weakened immunity, infection may cause a serious and occasionally fatal illness, toxoplasmosis.