Bacterial outbreak in China infects thousands of people after factory leak

Several thousand people in north-east China have tested positive for bacterial disease in an outbreak caused by a leak at a biopharmaceutical company last year, authorities said on Tuesday. The Health Commission of Lanzhou, the capital city of Gansu province, announced that 3,245 people had contracted the disease brucellosis. The disease is often caused by contact with livestock carrying the bacteria brucella, CNN reported.

This outbreak began from a leak at the Zhongmu Lanzhou biological pharmaceutical factory, which occurred between late July to late August last year, according to the city's Health Commission. Another 1,1401 people have also tested positive of the disease but there have been no fatalities have been reported, the city's Health Commission said. In total, authorities have tested 21,847 people out of the city's 2.9 million population. The disease, also known as Malta fever or Mediterranean fever, can cause symptoms including headaches, muscle pain, fever and fatigue.

While some symptoms can become chronic or never go away, like arthritis or swelling in certain organs, according to the United States' Centers for Disease Control and Prevention (CDC).

Human-to-human transmission is extremely rare, according to the CDC. Instead, most people are infected by eating contaminated food or breathing in the bacteria -- which seems to be the case in Lanzhou.

While producing Brucella vaccines for animal use, the factory used expired disinfectants and sanitizers -- meaning not all bacteria were eradicated in the waste gas.

This contaminated waste gas formed aerosols that contained the bacteria -- and leaked into the air, carried by the wind down to the Lanzhou Veterinary Research Institute, where the outbreak first hit.

In the months after the outbreak, provincial and municipal officials launched an investigation into the leak at the factory, according to the Lanzhou Health Commission. By January, authorities had revoked vaccine production licenses for the plant and withdrew product approval numbers for its two Brucellosis vaccines.

A total of seven veterinary drug product approval numbers were also cancelled in the factory.

In February, the factory issued a public apology and said it had "severely punished" eight people who were determined as responsible for the incident. It added.