China's respiratory outbreak is 'expected' and not caused by new virus

In mid-November, news broke of an outbreak of respiratory illness in China, raising concerns that another pandemic like COVID-19 might emerge. Now, scientists say the pathogens behind the surge are actually quite common. 

The worries of another pandemic started Nov. 13, when China's National Health Commission announced a nationwide increase in respiratory infections, mainly in children, according to the World Health Organization (WHO). Then, on Nov. 21, various media outlets reported clusters of cases of "undiagnosed pneumonia" in children in northern China, notably in Beijing and Liaoning province. The Program for Monitoring Emerging Diseases (ProMED), an international network for disease surveillance, also amplified similar news reports. 

This prompted the WHO to investigate, and on Thursday (Nov. 23), the organization confirmed that the reported increase in infections and hospitalizations among children is actually being caused by several known pathogens. 

These pathogens include the bacterium Mycoplasma pneumoniae, respiratory syncytial virus (RSV), adenoviruses and influenza. M. pneumoniae can cause bacterial pneumonia, while RSV, adenoviruses and influenza can cause viral pneumonia in severe cases.    

Chinese health authorities also told the WHO that they haven't detected any "unusual or novel pathogens or unusual clinical presentations, including in Beijing and Liaoning." In other words, this rise in infection is being caused by multiple known culprits, not a mysterious monster bug. 

Related: Who should get the new COVID vaccines? What to know about the 2023-2024 shots

"This is not an indication of a novel pathogen; This is expected," Maria Van Kerkhove, acting director of the WHO's department of epidemic and pandemic preparedness and prevention, told STAT News.  

"This is what most countries dealt with a year or two ago," when they began to lift restrictions enacted in the early pandemic, she said. China only loosened its quarantining and testing policies in December 2022.

Now that pandemic restrictions have been eased, children are more likely to catch bugs this winter that they were sheltered from before. This also means that their immune systems have not been exposed to many common viruses, and as a result, they have not yet acquired protective immunity against them — something known as an "immune deficit," Dr. Ben Marais, director of the Sydney Infectious Diseases Institute at the University of Sydney, told the Australian Science Media Centre (SMC). Children are also more likely to develop severe RSV infection and to be infected by M. pneumoniae than adults.

In addition, respiratory infections normally surge in winter. 

"This is a typical 'winter surge'' in acute respiratory infections," Benjamin Cowling, a professor of epidemiology at the University of Hong Kong, told Nature. "It is happening slightly earlier this year, perhaps because of increased population susceptibility to respiratory infections resulting from three years of COVID measures," he said. 

China also recently enhanced its disease surveillance systems, Paul Arbon, a professor at Flinders University in Australia who researches health emergencies and health system strengthening, told the Australian SMC. 

"There has been an uptick in the rates but it is that time of year and China has implemented a new national reporting system that has, as it should, picked up cases that were not reported under the old system," he said. The WHO also noted that these enhancements "may have contributed to the observed increase in detection and reporting of respiratory illness in children." 

Other countries saw similar waves of respiratory infections in children during the first winter after lifting lockdown restrictions, Francois Balloux, a professor of computational systems biology at University College London, told the U.K. SMC. In the U.S., for example, more people were hospitalized with flu in November 2022 than at any point since 2010, according to the Centers for Disease Control and Prevention (CDC). 

The WHO is still closely monitoring the outbreak in China and remains in contact with local health authorities, according to the Nov. 23 statement.

The WHO recommends that people in China follow standard measures to reduce the risk of infection, such as getting vaccinated as appropriate, wearing face masks and maintaining a safe distance from people who are ill. 

As for the rest of the world, the WHO currently advises against travel or trade restrictions, and it hasn't introduced any specific measures for people traveling to China. However, anyone who develops symptoms of respiratory illness while traveling should seek medical attention, the WHO recommends.

This article is for informational purposes only and is not meant to offer medical advice.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!