This disease is usually caused by contact with animals.
People are still being treated in hospital despite the outbreak a year ago.
China‘s legislature issued a law last month to establish a biosecurity risk prevention and control protocol, and a system for responding to risks including sudden outbreaks.
What is Brucellosis?
This disease is caused by bacteria that attack sheep, goats, cows, pigs and even dogs. This disease has also been reported in many countries.
Humans generally contract the disease through direct contact with infected animals.
Transmission can be through consumption of contaminated animal products, such as unpasteurized milk or cheese, or through inhalation of airborne agents.
When someone is infected with brucellosis, the symptoms that appear include fever and weakness. These symptoms appear for several weeks after infection.
The death rate from brucellosis is quite low, but it does not rule out complications that can cause death.
Some symptoms such as joint pain can become chronic and never go away.
What happened in Lanzhou?
The latest outbreak in Lanzhou was first discovered in November 2019 when several students at the Lanzhou Animal Research Institute tested positive for brucellosis.
According to Chinese health authorities, as of the end of December at least 181 people at the institute had been infected with brucellosis.
According to Chinese state media reports, the outbreak has even spread to Heilongjiang province in China‘s northeast corner, where 13 people who worked at a veterinary institute in August 2019 tested positive.
The government has tested 55,725 people in the city, 6,620 of whom have tested positive for brucellosis to date, the Lanzhou government said at a news conference, according to a report on Thursday by Global Times.
The factory has used a disinfectant that expires in July through August 2019 to make a brucellosis vaccine, leaving bacteria in its waste gas.
The contaminated gas then forms an aerosol which flows downwind to the veterinary institute.
Is brucellosis common in China?
About half a million infected people are reported annually worldwide, with China usually numbering in the tens of thousands.
In 2019, China reported 44,036 cases with one death, up from 37,947 cases and zero deaths a year earlier.
Brucellosis is more common in pastoral areas in western and northern China. It is categorized as a Class B infectious disease under a three tier system
Last year, China reported more than 10 million cases of infectious diseases including brucellosis, dengue fever and dysentery.