The World Health Organization (WHO) has stated that the recent uptick in acute respiratory infections and corresponding pathogen detections reported across Northern Hemisphere countries is a normal occurrence for this time of year.
The WHO emphasized that China’s levels of acute respiratory infections, including human metapneumovirus (hMPV), are consistent with seasonal expectations, and no unusual outbreak patterns have been observed. According to Chinese officials, the healthcare system is functioning well, with hospital utilization currently lower than it was at the same time last year. There have been no emergency declarations or significant responses triggered, and public health measures have been implemented to curb the spread of respiratory infections.
In light of these circumstances, the WHO has advised against imposing travel or trade restrictions related to these trends in acute respiratory infections. This announcement follows a review by India’s central health authorities, which found no unusual surge in respiratory infections within the country.
hMPV is a common respiratory virus that usually circulates during the winter and spring months. Most individuals infected with hMPV experience mild upper respiratory symptoms similar to those of the common cold and typically recover within a few days, although some cases may require hospitalization due to bronchitis or pneumonia.
In response to global concerns regarding the rise in respiratory viruses in China, particularly hMPV, the WHO pointed out that China has a robust surveillance system for influenza-like illness (ILI) and severe acute respiratory infections (SARI), including hMPV. The Chinese Center for Disease Control and Prevention (CDC) conducts routine virological monitoring of prevalent respiratory pathogens and publishes detailed reports weekly. However, such comprehensive surveillance and data reporting are not uniformly available from all countries.
As of December 29, 2024, data from the China CDC shows a seasonal increase in common acute respiratory infections, including those caused by influenza viruses, respiratory syncytial virus (RSV), and hMPV, which aligns with expectations for this winter season. Currently, influenza is the primary virus detected, with the highest positivity rates among all monitored pathogens across various age groups, except in children aged 5 to 14, where mycoplasma pneumoniae has the highest positivity rate. Although there has been a slight increase in reported severe COVID-19 cases, the activity of SARS-CoV-2 remains low.
The predominant variant of SARS-CoV-2 detected in China is XDV and its sub-lineages, which account for 59.1% of sequenced samples. ILI activity has been increasing in both northern and southern provinces since late 2024, following similar trends from the previous year. While ILI levels in the southern provinces remain below those of the last two years, activity in the northern provinces is comparable to previous years at this time.
The seasonal rise in acute respiratory infections is attributed to the typical epidemics of various respiratory pathogens, including seasonal influenza, RSV, and hMPV, along with mycoplasma pneumoniae. The WHO noted that the simultaneous circulation of multiple respiratory pathogens during winter can sometimes strain healthcare systems as they care for ill patients.
In several Northern Hemisphere countries, rates of influenza-like illness and acute respiratory infections have increased recently, exceeding baseline levels, which aligns with seasonal trends. Influenza activity is notably high in many regions of Europe, Central America, the Caribbean, West and Central Africa, and various Asian countries. Meanwhile, SARS-CoV-2 activity, as monitored through sentinel surveillance and wastewater analysis, remains low in Northern Hemisphere countries.
