The increase in acute respiratory infections and associated pathogen detections reported from countries in the Northern hemisphere is “expected” and “not unusual” for this time of year, the World Health Organization said in its latest risk assessment of trends engaging health administrators across the world.  

“China’s reported levels of acute respiratory infections, including hMPV (human metapneumovirus) are within the expected range for the winter season with no unusual outbreak patterns reported. Chinese authorities confirmed that the health care system is not overwhelmed, hospital utilization is currently lower than this time last year, and there have been no emergency declarations or responses triggered,” the WHO said, adding that Chinese authorities had put out public health messages to prevent the spread of respiratory infections, following the seasonal increase.

Based on its current risk assessment, the WHO has advised against travel or trade restrictions linked to trends in acute respiratory infections.

The statement comes even as India’s central health authorities reviewed the domestic situation with states and  reiterated that no unusual increase in respiratory infections had been picked up.

The hMPV is a common respiratory virus found to circulate in many countries in winter through to spring, the WHO said. “While some cases can be hospitalized with bronchitis or pneumonia, most people infected with hMPV have mild upper respiratory symptoms similar to the common cold and recover after a few days,” it added.

China increase

Responding to international interest in the increase of respiratory virus transmission in China, particularly hMPV, and suggestions of hospitals being overwhelmed, the WHO said, “China has an established sentinel surveillance system for ILI (influenza like illness) and severe acute respiratory infections (SARI), including hMPV, and conducts routine virological surveillance for common respiratory pathogens with detailed reports published weekly on the China Center for Disease Control and Prevention (CDC) website. Surveillance and laboratory data for hMPV is not available routinely from all countries.”

According to China CDC data (upto 29 December 2024), there has been an upward trend of common acute respiratory infections, including those due to seasonal influenza viruses, RSV (respiratory syncytial virus) and hMPV – as expected for this time of year during the Northern Hemisphere winter, the note said.

“Influenza is currently the most reported cause of respiratory disease, with the highest positivity rate among all monitored pathogens for all age groups except children aged 5-14 years for whom mycoplasma pneumoniae had the highest positivity rate. SARS-CoV-2 activity remains low however with an increase in reported severe COVID-19 cases,” it said.

The predominant circulating SARS-CoV-2 variant in China is XDV and its sub-lineages accounting for 59.1 per cent detection among sequenced samples. “ILI activity in China’s northern and southern provinces have been increasing since late 2024, following the previous year’s trends. Current ILI activity in the southern provinces remains below that of the previous two years, while current ILI activity in the northern provinces is similar to levels seen at this time in the previous two years,” it added.

Situation report

The increase in acute respiratory infections during these months are caused by seasonal epidemics of respiratory pathogens such as seasonal influenza, RSV, and other common respiratory viruses, including hMPV, as well as mycoplasma pneumoniae, the WHO said. “The co-circulation of multiple respiratory pathogens during the winter season can sometimes cause an increased burden on health care systems treating sick persons,” the WHO said.

In some countries in the Northern hemisphere, influenza-like illness  and/or acute respiratory infection  rates have increased in recent weeks and are above baseline levels, following usual seasonal trends. Influenza activity is elevated in many countries in Europe, Central America and the Caribbean, Western Africa, Middle Africa, and many countries across Asia, it said.

SARS-CoV-2 (the virus that caused the pandemic) activity as detected in sentinel surveillance and reported to Global Influenza Surveillance and Response System, along with wastewater monitoring from the reporting countries, is currently low in countries in the Northern hemisphere, it added.