According to Reuters, the Health Commission of the City of Lanzhou in Gansu Province, China, reported confirmed cases of brucellosis in July 2019 as a result of an accidental release of contaminated air from a vaccine plant.  According to the Health Commission, 3,200 known cases and at least 1,500 presumptive cases were identified among 21,000 individuals sampled in the city of Lanzhou with a population of 2.9 million.

Investigations showed that the Zhongmu Lanzhou Pharmaceutical plant failed to adequately inactivate waste allowing the release of viable Brucella mellitensis bacteria into an exhaust air stream.  The failure was attributed to either misuse of disinfectants or using expired and inactive products according to the Health Commission.  Many of the cases occurred in the adjoining Lanzhou Veterinary Research Institute and among students and faculty at the Lanzhou University.

Brucellosis is rare in industrialized countries and the incidence rate has declined sharply in China since the 1980s following control measures including vaccination of livestock and pasteurization of milk.

Brucellosis is a chronic disease resistant to treatment and usually acquired from direct contact with infected livestock, aborted fetuses or consumption of raw milk from infected cattle and goats.