Trends in Acute Respiratory Infections in the Northern Hemisphere
In many countries of the Northern Hemisphere, trends in acute respiratory infections increase at this time of year. These increases are typically caused by seasonal epidemics of respiratory pathogens such as seasonal influenza, respiratory syncytial virus (RSV), and other common respiratory viruses, including human metapneumovirus (hMPV), as well as mycoplasma pneumoniae. The co-circulation of multiple respiratory pathogens during the winter season can sometimes cause an increased burden on health care systems treating sick persons.
Current Situation
Currently, in some countries in the temperate Northern hemisphere, influenza-like illness (ILI) and/or acute respiratory infection (ARI) 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. Seasonal influenza type and subtype vary by location, typical for this time of year, except during most of 2020 and 2021, when there was little influenza activity during the COVID-19 pandemic. SARS-CoV-2 activity is currently low in countries in the Northern hemisphere. Where surveillance data is available, trends in RSV activity vary by region with downward trends observed in most subregions of the Americas. Some countries in the Northern hemisphere have reported increased trends in hMPV, among other respiratory pathogens, in recent weeks, in line with seasonal patterns.
China’s Situation
China has reported an increase in respiratory virus transmission, particularly hMPV, with suggestions of hospitals being overwhelmed. Surveillance and laboratory data for hMPV is available in China where routine virological surveillance for common respiratory pathogens is conducted and detailed reports are published weekly on the China Center for Disease Control and Prevention (CDC) website. China continues to monitor acute respiratory infections and reports an upward trend in cases due to seasonal influenza viruses, RSV, and hMPV. Influenza is currently the most reported cause of respiratory disease in China, with the highest positivity rate among all monitored pathogens for all age groups.
Preventative Measures
Based on the expected increase in respiratory infections during the winter season, countries, including China, have been providing health messages to the public on how to prevent the spread of respiratory infections and reduce the impact of disease. WHO recommends that individuals take normal precautions to prevent the spread of respiratory pathogens, especially to the most vulnerable. It is advised to stay home if experiencing mild symptoms, seek medical care for severe symptoms, wear masks in crowded spaces, practice regular handwashing, and follow recommended vaccination guidelines.
WHO advises Member States to maintain surveillance for respiratory pathogens through an integrated approach and has published guidance on assessing influenza epidemic and pandemic severity. Based on the current risk assessment, WHO advises against any travel or trade restrictions related to current trends in acute respiratory infections.
