Naturally acquired aflatoxicosis in humans is extremely rare in Western societies. A single case may represent a terrorist event. In 1995, Iraq admitted to having weaponized aflatoxins.

Naturally occurring aflatoxicosis is caused by the ingestion of one of the classes of toxins found in certain fungi called aflatoxins, which are produced by Aspergillus flavus, Aspergillus parasiticus, and other strains of Aspergillus. The 4 aflatoxins of concern are B1, B2, G1, and G2. However, B1 is the most predominant and toxic to humans and animals. Aflatoxin contamination is typically found in grains and tree nuts, peanuts and peanut products, corn and corn products, cottonseed oil, and milk. Contamination can occur at any stage, including prior to harvest or during production, processing, transport, or storage. Standard plant-disease–prevention strategies have been unsuccessful in controlling aflatoxin.

An outbreak of aflatoxicosis in India resulted in a 27% mortality rate, while a later outbreak in Kenya had a 60% mortality rate.

In humans, aflatoxicosis is classified as acute or chronic. A high initial exposure to aflatoxins will produce acute hepatic necrosis from days to weeks later, but with multiple exposures likely in a terrorist attack, many victims will present with acute hepatic necrosis within a short period of time. Patients will appear ill with fever, jaundice, nausea, vomiting, abdominal pain, and hemorrhagic diathesis, hepatomegaly, and elevated liver function tests. Patients may also develop limb edema, pulmonary edema, seizures, coma, and death.

Chronic aflatoxicosis results in impaired food conversion and stunted growth. Aflatoxicosis is not transmissible. It is most often seen in developing nations, especially in times of drought, and is further impacted by nutritional status, health, the level and duration of exposure, and comorbid conditions such as viral hepatitis or parasitic infection. No cases of aflatoxicosis in humans have been reported in the United States. Cases in animals have been sporadic. Aflatoxins are included on the International Agency for Research on Cancer list of human carcinogens. There is a positive association between dietary aflatoxins and hepatocellular carcinoma.