The HPA Influenza Pandemic Contingency Plan outlines the Health Protection Agency’s plan for responding to an influenza pandemic. It replaces the Public Health Laboratory Service Pandemic Influenza Plan of July 2001.
Influenza is a familiar infection in the UK, especially during winter. Almost every year new drifted strains of influenza emerge giving rise to morbidity and mortality, mainly in older persons and young children. Pandemic influenza is different: its emergence and potential impact are both difficult to predict.
A pandemic of influenza is the result of a new influenza A virus subtype emerging which is markedly different from recently circulating strains and is able to:
- infect people (rather than, or in addition to, animals or birds)
- spread from person to person, and
- cause illness in a high proportion of the people infected, and also
- spread widely, because a high proportion of the population is susceptible (most people will have little or no immunity to the new virus because they will not have been infected or vaccinated with it or a similar virus before).
New subtypes of influenza have emerged sporadically over the last century. In 1918 a devastating and unusual pandemic caused by influenza A, subtype H1N1 (‘Spanish flu’) killed between 20 and 40 million people worldwide. Other pandemics that followed had a less devastating impact but were nevertheless severe. Influenza A, subtype H2N2 (‘Asian flu’) emerged in 1957 and H3N2 (‘Hong Kong flu’) in 1968.