The geographical spread of the 1947 poliomyelitis epidemic in England and Wales: spatial wave propagation of an enigmatic epidemiological event

The 1947 epidemic of poliomyelitis was the largest and geographically most widespread outbreak of the disease ever recorded in England and Wales. As a transitional event in the history of poliomyelitis in the British Isles, the 1947 epidemic signalled the sudden onset of a sustained period of heightened epidemicity that continued until the introduction and mass administration of safe and effective poliovirus vaccines in the late 1950s. This paper explores the apparent shift in the spatial dynamics of poliovirus that underpinned the geographical spread of the 1947 epidemic in England and Wales. Drawing on a robust method of spatial epidemiological analysis (swash–backwash model), we demonstrate that the epidemic wave was associated with a pronounced acceleration in the rate of spatial propagation as compared to the preceding years. The velocity of spatial expansion and retreat and the duration of infectivity are shown to have varied by category of geographical area and by county of England and Wales. The weight of available evidence suggests that the so-called ‘hygiene model’ of the epidemic emergence of poliomyelitis, developed in the context of Western countries and generally assumed for England and Wales, does not adequately account for the events of 1947. Rather, we suggest that the features of the epidemic are consistent with the introduction and spread of one or more new strains of poliovirus in England and Wales in the summer of 1947. Possible connections to the epidemic occurrence of poliomyelitis in other European countries at about this time are considered.

► The 1947 poliomyelitis epidemic is modelled using a robust spatial method.
► Phase transitions are used to measure the spatial velocity of the epidemic wave.
► Epidemic expansion is characterised by a high degree of local spatial contagion.
► Our results are consistent with the spread of a new strain of poliovirus in 1947.