The surge in respiratory infections in young children in northern China is being driven primarily by known viral and bacterial infections and not by a novel pathogen, the World Health Organization (WHO) said late last week in an update.
Following a request for data and discussions with Chinese health officials on November 23, the WHO said the increase in outpatient consultations and hospital admissions of children in China is linked to increased circulation of pneumonia caused by Mycoplasma pneumoniae—commonly known as "walking pneumonia"—since May and a more recent uptick in respiratory syncytial virus (RSV), adenovirus, and influenza. That conclusion was based on data from enhanced surveillance systems for respiratory illnesses implemented in China in mid-October.
"Some of these increases are earlier in the season than historically experienced, but not unexpected given the lifting of COVID-19 restrictions, as similarly experienced in other countries," the WHO said.
Officials with the Chinese Center for Disease Control and Prevention and the Beijing Children's Hospital told the WHO that there has been no detection of any unusual or novel pathogen, nor any change in disease presentation. They also said the increase in respiratory illness in children has not exceeded local hospital capacities.
The WHO said that while the limited information available makes it difficult to characterize the overall risk to children in China, respiratory illnesses are likely to increase with the arrival of winter, and that "co-circulation of respiratory viruses may increase burden on health care facilities."
'Immunity gap' may play a role
The WHO requested the additional epidemiologic and clinical information from Chinese officials following reports early last week of children's hospitals in Beijing, Liaoning, and other parts of China that were swamped with children who had undiagnosed pneumonia.
One TV report showed a lobby of a children's hospital filled with children receiving intravenous drips. The reports also noted that the number of sick children had led to cancellation of classes in parts of the country, with some parents accusing the government of a cover-up.
Those reports, which were flagged by ProMED Mail (the online reporting system for the International Society for Infectious Diseases), raised public fears because they evoked the reports of a mysterious pneumonia outbreak—eventually identified as SARS-CoV-2— in Wuhan in late 2019.
Some of these increases are earlier in the season than historically experienced, but not unexpected given the lifting of COVID-19 restrictions, as similarly experienced in other countries.
But in an interview with Stat, Maria Van Kerkhove, PhD, acting director of the WHO's department of epidemic and pandemic preparedness and prevention, said the information provided by Chinese officials suggests an immunity gap created by COVID-19 lockdowns is likely responsible for the surge in pediatric respiratory illnesses.
"This is not an indication of a novel pathogen," Van Kerkhove said. "This is expected. This is what most countries dealt with a year or two ago."
China's Zero COVID policy was far stricter, and kept the country under lockdown for far longer, than other countries. In addition to limiting the spread of COVID, it also prevented many children from being exposed to other respiratory illnesses. The WHO said that, at a November 13 press conference, China's National Health Commission attributed the recent increase in pediatric respiratory illness to the lifting of COVID-19 restrictions and the arrival of the cold season.
In an October 13 report from China Daily cited by the FluTrackers blog, Chinese clinicians said cases of walking pneumonia in children had been rising since June. They also noted that, prior to COVID-19, outbreaks of M pneumoniae in China occurred every 3 to 7 years.
In its most recent Communicable Disease Threats Report, the European Centre for Disease Prevention and Control said an increase in pediatric respiratory infections during the winter months is not unexpected, and noted that European Union/European Economic Area countries and the United Kingdom are also reporting significant increases in respiratory infections in children.
