The impact of three influenza epidemics on primary care in England and Wales.

The numbers of persons with influenza presenting to general practitioners in England and Wales during the epidemics of late 1989, late 1993, and early 1995 are estimated to be approximately 760,00, 480,000 and 192,000, respectively. The expected numbers used to derive these estimates were obtained by averaging incidence by week over the 9 winters of 1986/87 to 1994/95, excluding those weeks in which influenza was prevalent. These 3 epidemics varied in magnitude and in the relative impact on persons in different age groups. The influenza B epidemic in 1995 scarcely affected elderly people. During the 3 epidemic periods, increased numbers of persons consulted their general practitioners with other respiratory diseases, including pneumonia, acute bronchitis and otitis media. The patterns of increase were not consistent between the epidemics, partly because of the differing impact on the various age groups and partly because of the effect of other respiratory viral illnesses prevalent at the same time. No increase occurred in the numbers of persons reported with new episodes of cerebrovascular accident or of acute myocardial infarction. A similar method was used to estimate excess deaths, which amounted to 25,000 in 1989, 13,000 in 1993, and 500 in 1995. In the periods immediately following the influenza epidemics, the observed pattern of deaths conformed to the expected, demonstrating that persons dying during the epidemics were not just dying a few weeks prematurely.