Pandemic flu: implications for sexual and reproductive health services.

©FSRH J Fam Plann Reprod Health Care 2009: 35(4) Introduction A new pandemic of influenza (flu) has been anticipated for some time: the last actual flu pandemic occurred in 1969/1970. [NB. A pandemic is defined as an epidemic of infectious disease that is spreading through human populations across a large region.] Pandemics of flu occur whenever the prevalent circulating strain of the flu virus changes its antigenic composition significantly, a process known as antigenic shift. When this happens, the ‘new’ strain is identified as HxNy, where H and N refer to the major antigens (haemaglutinin and neuraminidase) and ‘x’ and ‘y’ refer to their latest molecular shape. The current pandemic flu strain, also known as ‘swine flu’, is classified as H1N1 and resembles the ‘Spanish flu’ pandemic strain that caused global mortality during 1918/1919. The case definition for swine flu is well described elsewhere (see Box 1), but a fever of at least 38°F is usually considered a prerequisite for diagnosis. However, and perhaps because the swine flu strain is not an entirely new form of the flu virus, up until now the clinical picture of swine flu has been that of a characteristic, but only moderately severe, illness. Certain population groups appear to be more severely affected, however: these include pregnant women, and all people with underlying chronic medical conditions, especially respiratory, and those with immunosuppression. Older people appear to have been less severely affected, perhaps because they have some residual immunity from the tail of the earlier H1N1 pandemic. Children have a high chance of contracting the illness, and the mortality rate, although low overall, has been higher within this age group to date. Death may be due to the primary impact of the virus on respiratory tissue or (more usually) as a consequence of secondary pneumonia. Antiviral medication is available for those with confirmed swine flu; however, its main impact is to shorten the duration of illness, rather than its severity. A mass immunisation programme is planned in the UK from October 2009: this will itself pose major organisational challenges to the National Health Service. Frontline health care workers will be offered this vaccine alongside other priority groups.