The Health Commission of Lanzhou, the capital of Gansu province, confirmed that 3,245 people had contracted the disease brucellosis, which is often caused by contact with domestic animals carrying the bacteria brucella.
A further 1,401 people have tested positive so far, although no deaths have been reported, the city’s health commission said. In all, authorities tested 21,847 people out of the city’s 2.9 million inhabitants.
Transmission between humans and humans is extremely rare, according to the CDC. Instead, most people become infected by eating contaminated food or inhaling the bacteria ̵
This outbreak stemmed from a leak at Zhongmu Lanzhou Biological Pharmaceutical Factory that took place between late July to late August last year, according to the city’s health commission. While producing Brucella vaccines for animal husbandry, the factory used expired disinfectants and disinfectants – meaning that not all bacteria were eradicated in the waste gas.
This polluted waste gas formed aerosols that contained the bacteria – and leaked into the air, carried by wind down to the Lanzhou Veterinary Research Institute, where the eruption first hit.
Other infected patients included students and faculty members from Lanzhou University; the outbreak even spread to Heilongjiang province, on the very northeastern tip of the country, where 13 positive cases had worked at the veterinary institute in August, Xinhua reported at the time.
A total of seven veterinary drug approval numbers were also canceled at the factory.
In February, the factory issued a public apology, saying it had “severely punished” eight people determined to be responsible for the incident. It added that it would cooperate with local authorities in the response and clean-up efforts and contribute to a compensation program for those affected.
The Lanzhou Health Commission also announced in its report on Tuesday that 11 public hospitals would provide free and regular check-ups for the infected patients. The report did not provide further details on compensation to patients, except that it would be launched in batches from October.