Pneumonia Complicating Asian Influenza

Abstract

The epidemic of influenza which later became known as " Asian 'flu " apparently originated in China in February, 1957, and its causative organism, a new variant of influenza virus A, was first identified in cases which occurred in Hong Kong in April, 1957 (Meyer, Hilleman, Miesse, Crawford and Bankhead, 1957).The epi- demic spread rapidly across Asia and Europe, and appeared sporadically in Britain during the summer months.The first wave of infection occurred in York- shire; it spread almost immediately to the North and more slowly to the South, the North having the more severe experience (Martin, 1958).Local outbreaks developed in many places in the latter half of August, but October was the peak month, and the infection had virtually disappeared by the end of November.Asian influenza attacked an estimated twelve million people in Britain, and was directly or indirectly respon- sible for about 16,000 deaths, two-thirds of the fatalities being in persons over the age of 55 (W.H.O.Weekly Epidemiological Record, 1958).The mortality rate was not exceptional, possibly owing in part to the outbreak having passed its peak before the usual minor respiratory infections and winter ailments had become widespread.The incidence of pulmonary complications, principally pneumonia, was also low, figures for general practices being 3.5% of 750 (Fry and Hume, 1957) and 5% of 542 (Edmundson and Hodgkin, 1957), and amongst R.A.F.' recruits 5% of 391 (Gilroy, 1957); it increased steadily as the epidemic progressed (Cantor, 1957; Gil- roy, 1957).No accurate figures are available to indicate the frequency of pneumonia amongst emergency hos- pital admissions for Asian 'flu, but it is unlikely to have been much in excess of one-half, at least so far as London hospitals were concerned; this was also the