The World Health Organisation has asked China for more detailed information about an outbreak of a respiratory illness and reported clusters of undiagnosed pneumonia in children.
Since mid-October, the WHO said northern China had reported an increase in influenza-like illnesses compared with the same period in the previous three years.
In recent days, local media in cities such as Xian in the northwest have posted videos online of hospitals crowded with parents and children waiting to be seen by medics.
The WHO has responded by making an official request to China for additional information as well as laboratory results from the reported outbreaks among children.
In the meantime it has recommended Chinese communities take preventative measures including getting vaccinated, wearing masks, keeping a distance from sick people, staying at home when ill and regular hand-washing.
Chinese authorities have attributed the spike to a cold snap – and to the lifting of COVID-19 restrictions and the circulation of known pathogens including respiratory syncytial virus (RSV) and influenza – as well as common bacterial infections that affect children, including mycoplasma pneumonia.
As temperatures plummeted in the Chinese capital of Beijing, located in the north of the country, the city “entered a high incidence season of respiratory infectious diseases”, Wang Quanyi, deputy director and chief epidemiological expert at the Beijing Center for Disease Control and Prevention, told state media on Wednesday.
The city “is currently showing a trend of multiple pathogens coexisting”, he added.
On Wednesday, the WHO said groups including the Programme for Monitoring Emerging Diseases reported clusters of undiagnosed pneumonia in children in northern China.
The WHO said it was unclear if these were associated with an overall increase in respiratory infections previously reported by Chinese authorities – or separate events.
The WHO has also asked for further information about trends in the circulation of known pathogens and the burden on healthcare systems. It said it is in contact with clinicians and scientists.
The WHO’s office in China on Thursday described the action as a “routine” check.
An increase in incidence of respiratory disease was first disclosed during a news conference last week by Chinese officials from the National Health Commission.
Both China and the WHO have previously faced questions about the transparency of reporting on the earliest COVID cases.
Three years on from when the cases were first detected in the central Chinese city of Wuhan in the latter months of 2019 – there is still debate about the origins of the coronavirus outbreak.