Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. Most people recover from fever and other symptoms within a week without requiring medical attention. However, influenza can cause severe illness or death, particularly among high risk groups including the very young, the elderly, pregnant women, health workers and those with serious medical conditions.

Given the risk to vulnerable groups and the potential for seasonal influenza viruses to cause outbreaks and epidemics, WHO's Health Emergencies Programme monitors and assesses the spread of these viruses on an ongoing basis.