The World Health Organization (WHO) on Wednesday officially requested that China provide detailed information on an increase in respiratory illnesses and reported clusters of pneumonia in children.

Chinese authorities from the National Health Commission held a press conference on Nov. 13 to report an increase in incidence of respiratory diseases in the country, the WHO said in a statement.

The global health agency said Chinese authorities attributed the 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 the virus that causes COVID-19.

Chinese authorities stressed the need for enhanced disease surveillance in healthcare facilities and community settings, as well as strengthening the capacity of the health system to manage patients.

Both China and the WHO have faced questions about the transparency of reporting on the earliest COVID-19 cases which emerged in the city of Wuhan in late 2019 and early 2020.

On Wednesday, WHO said groups including the Program for Monitoring Emerging Diseases reported clusters of undiagnosed pneumonia in children in northern China. WHO said it is unclear if these are associated with the overall increase in respiratory infections previously reported by Chinese authorities, or separate events.

The health agency said it has requested additional epidemiologic and clinical information, as well as laboratory results from these reported outbreaks among children, through the International Health Regulations mechanism.

It has also asked China for further information about trends in the circulation of known pathogens and the current burden on health care systems. WHO said it is in contact with clinicians and scientists through its existing technical partnerships and networks in China.

Since mid-October, WHO said northern China has reported an increase in influenza-like illness compared to the same period in the previous three years. It said the country has systems in place to capture information on trends in illness incidence and to report that data to platforms such as the Global Influenza Surveillance and Response System.

WHO said that while it seeks additional information, it recommends that people in China follow measures to reduce the risk of respiratory illness, including vaccination; keeping distance from people who are ill; staying home when ill; getting tested and medical care as needed; wearing masks as appropriate; ensuring good ventilation; and regular hand-washing.