The World Health Organization on Wednesday said it has asked China for more information about an increase in respiratory illnesses and reported clusters of pneumonia among children in the north of the country.

Since mid-October, China has been experiencing an increase in cases of influenza-like illnesses compared with the same period in the previous three years when strict measures were in force as authorities enforced a zero-Covid strategy.

The World Health Organization had repeatedly criticised the Chinese government over the course of the pandemic, saying that the authorities were under-representing the true impact of the coronavirus outbreak in the country.

In 2019, the first cases of what later turned out to be Covid-19 were initially reported as viral pneumonia.

On November 13, Chinese authorities from the National Health Commission held a press conference to report an increase in the incidence of respiratory diseases.

“Authorities attributed this increase to the lifting of Covid-19 restrictions and the circulation of known pathogens such as influenza, mycoplasma pneumoniae [a common bacterial infection which typically affects younger children], respiratory syncytial virus, and SARS-CoV-2 [the virus that causes Covid-19],” a statement from the United Nations’ health body said.

The World Health Organization said that groups, including the Program for Monitoring Emerging Diseases, reported clusters of undiagnosed pneumonia in children in northern China. But it was not clear if these are associated with an overall increase in respiratory infections previously reported by Chinese authorities or separate events.

“On November 22, the WHO requested additional epidemiologic and clinical information, as well as laboratory results from these reported clusters among children, through the International Health Regulations mechanism,” the statement added.

The health body has also sought details about trends in the circulation of known pathogens and the burden on health-care systems. The statement said it was in contact with clinicians and scientists through its existing technical partnerships and networks in China.

The World Health Organization urged the Chinese public to take preventative measures, including getting vaccinated, keeping distance from those sick and wearing masks.