Global Alert and Response (GAR)

WHO Report on Global Surveillance of Epidemic-prone Infectious Diseases - Influenza


  • Influenza continues to cause considerable morbidity and mortality each year.
  • Epidemiological characteristics of influenza viruses, such as attack rate and virulence are unpredictable, and change from year to year.
  • There was an epidemic of avian influenza in chickens and ducks in Hong Kong Special Administrative Region, (SAR) in 1997 that was transmitted to humans. Fortunately, the virus did not transmit from person to person, and soon died out after the reservoir of domestic birds was completely depleted by the killing of approximately 1.6 million chickens, ducks and geese by Hong Kong (SAR) authorities. This type of jump in species is not a rare occurrence for influenza viruses and continued vigilance is necessary. The fact that the genetic analysis of this new strain was done in a timely manner is a positive indication for the functioning of the influenza surveillance network.
  • The influenza virus constantly mutates, and periodically causes worldwide pandemics to which almost everyone is susceptible.
  • No one knows when the next pandemic will occur.