Rapid gradual genetic and antigenic changes (drift) of the influenza virus are responsible for annual influenza epidemics of varying severity. A more dramatic type of antigenic variation, antigenic shift, can cause worldwide pandemics and occurs as a result of the reassortment between human and avian influenza viruses (pandemics of 1957 and 1968) or as a result of the direct introduction of an avian virus into human populations (outbreak of H5N1 influenza in Hong Kong, 1997). Even moderate influenza epidemics can cause excess mortality. For example, an average annual epidemic in the United States results in approximately 20,000 excess deaths. The impact of a pandemic would be much greater. It is estimated that between 90,000 and 200,000 deaths could occur in the US as a result of a pandemic. The impact of influenza can be reduced by annual vaccination. Optimal vaccine efficacy, however, can occur only when a close antigenic match between the vaccine strain and currently circulating viruses is achieved. Thus, influenza surveillance is focused primarily on selecting new vaccine strains in order to annually update the vaccine. The Influenza Branch of CDC actively participates in improving influenza surveillance in developing countries. The Branch: 1) distributes WHO Influenza Reagent Kits and other reagents necessary for influenza virus identification; 2) organizes and conducts international training courses in different countries; 3) provides bench training for visitors; 4) consults national authorities and WHO on the improvement of influenza control.
Learning Objectives: To demonstrate the importance of global influenza surveillance and the role of CDC in its improvement.
Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.