On May 23, 1938, Toxoplasma gondii (T. gondi) was identified in humans gondii was identified in an infant girl delivered full term by Caesarean section at Babies’ Hospital in New York City. The girl died at one month of age.

An autopsy discovered a lesions in her brain and eye tissue that were found to have been free of T. gondii. However, tissue from the girl inoculated intracerebrally into rabbits and mice developed encephalitis. The source of the T. gondii transmission was unknown.