China's health ministry on Sunday urged local authorities to increase the number of fever clinics as the country grapples with a surge in respiratory illnesses in its first full winter since easing COVID-19 restrictions.

The spike become a global issue last week when the World Health Organization asked China for more information, citing a report on clusters of undiagnosed pneumonia in children by the Program for Monitoring Emerging Diseases.

China and the WHO have faced questions about the transparency of reporting early in the pandemic, which emerged in the central Chinese city of Wuhan in late 2019. The WHO said on Friday no new or unusual pathogens had been found in the recent illnesses.

National Health Commission spokesperson Mi Feng said on Sunday the surge in acute respiratory illnesses was linked to the simultaneous circulation of several kinds of pathogens, most prominently influenza.

"Efforts should be made to increase the number of relevant clinics and treatment areas, appropriately extend service hours and strengthen guarantees of drug supplies," Mi told a news conference.

"It is necessary to do a good job in epidemic prevention and control in key crowded places such as schools, childcare institutions and nursing homes, and to reduce the flow of people and visits."

Cases among children are appearing especially high in northern areas like Beijing and Liaoning province, where hospitals are warning of long waits.

The State Council, China's cabinet, said on Friday that influenza would peak this winter and spring, while mycoplasma pneumoniae infection would remain high in some areas. It also warned of the risk of a rebound in COVID infections.

"All localities should strengthen information reporting on infectious diseases to ensure information is reported in a timely and accurate manner," the State Council said in a statement.

On Thursday the WHO said data provided by China suggested the recent cases were linked to the lifting of COVID curbs 11 months ago, along with the circulation of known pathogens like mycoplasma pneumoniae, a common bacterial infection that typically affects children, which has circulated since May.