2T78J5N SHANGHAI, CHINA - NOVEMBER 14, 2023 - Parents take their children to see a doctor at the pediatric emergency department of a hospital in Shanghai, China.
CNN  — 

The World Health Organization says it has requested more information from Chinese officials on an increase in respiratory illnesses and pneumonia clusters among children there.

Officials from China’s National Health Commission reported an increase in respiratory disease at a news conference last week, WHO said in a statement Wednesday.

“Chinese 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 (RSV), and SARS-CoV-2 (the virus that causes COVID-19),” WHO said.

Clusters of undiagnosed pediatric pneumonia cases have also been reported in the north of the country, the organization says, but it’s not clear whether these are related to the respiratory infections.

China maintained a policy known as zero-Covid – marked by strict lockdowns and quarantines, mass testing and rigorous contact tracing – until abandoning the strategy in December. These anti-Covid measures also limit the spread of more common germs, experts say, creating an “immunity gap” that can make people more vulnerable to infection when they stop taking such precautions.

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Media reports suggest “a widespread outbreak of an undiagnosed respiratory illness in several areas in China,” according to the International Society for Infectious Diseases’ Program for Monitoring Emerging Diseases, known as ProMED. “It is not at all clear when this outbreak started as it would be unusual for so many children to be affected so quickly,” but reports of illness predominantly in children suggest “some exposure at the schools.”

ProMED says that it is awaiting further information about the scope of the issue but that it’s too early to make any projections or speculations.

WHO says it has asked China for epidemiologic and clinical information, lab results from these clusters, details on trends in pathogen circulation and the burden on health care systems.

The agency advises people in China to take precautionary measures to lower the risk of respiratory illness, including getting recommended vaccines, staying home when sick, wearing masks around others and washing hands regularly.