The incident started in July 2019, lasted nearly a month later and was only recently revealed.

Brucella bacteria are rod-shaped and cause brucellosis, also known as wave fever or Mediterranean fever.

Initially, people believed that the smoke carrying bacteria originated from the Lanzhou Veterinary Research Institute, an animal infectious disease research facility.

However, authorities later confirmed that the bacteria flew from the direction of Lanzhou Biopharmaceutical Factory, part of China Livestock Enterprise.

Most of the affected people live about 1 km from the factory.

Other residents in the Yanchangbao neighborhood, around the Lanzhou Biopharmaceutical Factory, said they began experiencing mild fever and joint pain around September last year for unknown reasons.

People in Lanzhou province, China hold positive test results for brucella bacteria.

Although local officials confirm that patients will heal on their own over time, many people are still suffering from daily health damage, reducing their quality of life.

In January this year, a pregnant woman in her second month tested positive for bacteria.

The report said this was an accident, the exposure occurred in a short period of time.

Earlier this year, Lanzhou Biopharmaceutical Factory had its license to produce brucella vaccine and related approval documents revoked.

The factory also closed its factory in December last year, saying it would learn from experience and actively cooperate with local authorities to overcome the consequences and compensate for damages.

Outbreaks of the brucellosis bacteria frequently occur in Gansu province, an area whose economy is heavily dependent on agriculture.