Authorities in the northwestern Chinese city of Lanzhou said 3,245 people have tested positive for brucellosis as of Monday.

The city’s health commission said Tuesday that 21,847 people have been tested for the animal-borne disease causing flu-like symptoms, with 4,646 initially testing positive.

In a separate announcement about the disease, authorities added that those infected in Lanzhou, the capital of Gansu province, would not suffer serious health effects due to the “low strain” of the bacteria, and any symptoms would go away naturally in three to six months.

Brucellosis — also known as Malta, Mediterranean, or undulant fever — is a highly contagious zoonotic disease whose symptoms include fatigue, fever, sweating, and joint and back pain. The brucella bacterium is mainly found in livestock and dogs. While people in direct contact with infected animals can get the disease, there is no evidence of human-to-human transmission.

Official confirmation of the thousands of brucellosis infections comes eight months after dozens of cases were reported in Lanzhou late last year.

In December, 203 people in Gansu were infected with brucella after fumes from a local pharmaceutical factory making brucellosis vaccines were inadequately sterilized, resulting in the bacteria being released into the air, according to authorities. Of the 203 infections, 181 occurred at the Lanzhou Veterinary Research Institute and 22 at Lanzhou University. Both institutions are near the pharmaceutical factory.

More than 10,000 people live within a 1-kilometer radius of the factory, financial outlet Caixin reported last week. However, because of delayed diagnoses and treatment, the infections could become chronic for many: Half of the 40 residents in one housing community near the factory told Caixin they were still suffering from symptoms, although only two of them had been diagnosed by medical professionals.

Treatment for brucellosis requires an antibiotic regimen that must be strictly followed. If untreated, the disease can have serious adverse effects on internal organs and the digestive system. According to China’s Law on Prevention and Control of Infectious Diseases, brucellosis is considered a Class B disease, along with AIDS, SARS, and malaria.

On Tuesday, Lanzhou’s health commission said compensation for those who tested positive will be dispensed in installments beginning in October, though no actual amounts have been disclosed. The health authority added that it will conduct further medical checks and evaluations of the infected individuals.

Editor: Bibek Bhandari.

(Header image: A view of the Lanzhou Veterinary Research Institute building in Lanzhou, Gansu province, April 7, 2020. People Visual)