Exposure to pesticides and other agrochemicals sprayed on trees in lychee orchards has been linked to an outbreak of acute encephalitis syndrome (AES) in northern Bangladesh in 2012, according to a study in the American Journal of Tropical Medicine and Hygiene carried out by a collaborative team of clinicians, epidemiologists, and social scientists from Bangladesh and the United States.

The leading hypothesized cause of AES among children living near lychee orchards was the ingestion of phytotoxins present in lychee seeds and pulp. However, recurrent AES outbreaks reported around lychee orchards, particularly around harvest season, and the short duration between onset of illness to death led the scientists to suspect toxic poisoning rather than infection or lychee ingestion.