More than 3,000 people in China have contracted the bacterial disease known as Malta fever following a leak from a lab last year, health officials said.
The outbreak originating from the Zhongmu Lanzhou biological pharmaceutical factory left 3,245 people sickened with brucellosis, the Health Commission of Lanzhou said, according to a CNN report.
Authorities have tested a total of 21,847 people in Gansu province, which has a population of 2.9 million, and another 1,401 people have preliminarily tested positive.
No fatalities have been reported.
People can contract brucellosis — also known as Mediterranean fever — by coming into contact with livestock such as sheep, goats, cows or camels infected with the Brucella bacteria, the US Centers for Disease Control and Prevention said.
Symptoms include fever, sweating, headache, fatigue and pain in muscles and joints.
The most common way to become infected is by eating or drinking unpasteurized or raw dairy products, but humans can also fall ill by breathing in the bacteria.
The lab leak occurred last year between late July and late August when the factory was producing Brucella vaccines for animal use, the Health Commission said. The factory was using expired disinfectants and sanitizers and not all bacteria were killed in the waste gas, CNN reported.
That left the bacteria floating in the air, which carried it down to the Lanzhou Veterinary Research Institute, where Brucellosis infections were reported in November.
Other infections occurred among students and staff at Lanzhou University and the outbreak even spread to Heilongjiang province in the northeastern part of the country.
An investigation was launched, with authorities stripping the factory of its vaccine production licenses and yanking approvals for two Brucellosis vaccines. Seven total veterinary drug approvals were also canceled.
In February, the factory said it “severely punished” eight people who were deemed responsible for the leak and issued an apology.