Chinese authorities reportedly called for vigilance Friday as a spike in respiratory illness continues to pile pressure on health care facilities in the north of the country, despite assurances that no "unusual or novel pathogens" have been detected.

The World Health Organization said Thursday that Beijing had responded to its request for data following reports of "clusters of undiagnosed pneumonia in children's hospitals in Beijing, Liaoning and other places in China." Chinese health authorities said no changes in disease presentation had been reported, according to the WHO.

China has been facing a surge in respiratory infections such as influenza and clusters of pneumonia among children, with hospitals particularly in northern China reporting that they are "overwhelmed" with patients.

The WHO said that the surge was likely linked to the lifting of Covid-19 restrictions as China experiences its first full winter season since declaring an end to the pandemic in December.

The U.N. health body said that current data suggests that the pathogens are currently behaving in typical ways that are treatable with existing antibiotics, but added that China should reinforce measures to limit the spread of the disease including via vaccines and mask-wearing.

It also said it does not recommend any specific measures for travelers to China and advised against the application of any travel or trade restrictions at this time.

China's State Council said in an update Friday that influenza cases, which have surged since October, would likely peak this winter and spring, according to Reuters. However, it added that pneumonia infections, which have been rising since May, could persist further into the future.

It said that local authorities should "strengthen information reporting on infectious diseases to ensure information is reported in a timely and accurate manner."

Both China and the WHO have come under scrutiny over their reporting of the earliest Covid-19 cases in 2020.

The WHO said that it will continue to monitor the current outbreak in China and that it is working with international partners to assess the emerging information.

The U.K. Health Security Agency said in a statement Friday that it was important to "keep an open mind" about new outbreaks.

It follows a surge in Strep A infections among children in the U.K. in 2022, which the health agency attributed to a change in social mixing patterns.