Influenza is an acute viral infection that spreads easily from person to person in any age group and that can cause serious complications in certain risk groups. In addition to seasonal epidemics, influenza pandemics can occur when a new influenza virus subtype emerges or when an animal influenza virus begins to spread among humans. 

Influenza epidemics and pandemics cause significant morbidity and mortality, costs to health services and economic losses due to work absenteeism. The 2009 pandemic alone is estimated to have caused 100 000–400 000 deaths, not only among groups considered to be at a higher risk of complications, such as the elderly, persons with chronic conditions and pregnant women, but also in young, healthy individuals.

WHO/Europe and key partners (European Centre for Disease Prevention and Control, the United States Centers for Disease Control and Prevention and WHO collaborating centres) aim to reduce influenza-related morbidity and mortality by: 

  • strengthening virological and epidemiological surveillance for mild and severe influenza;
  • using surveillance data to estimate the burden of influenza in order to prioritize national influenza vaccination programmes; and
  • maintaining and strengthening pandemic preparedness activities at the national level.

Other respiratory pathogens

WHO/Europe also monitors the emergence of other respiratory pathogens that have the potential to spread among humans. These include coronaviruses, which cause a range of illnesses from severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome coronavirus (MERS-CoV) to the common cold.