Figure 6.25 Poliomyelitis in England and Wales, 1944–8: leading and following edges of poliomyelitis activity in England and Wales. Graphs plot the cumulative percentage of administrative units (county, metropolitan and municipal boroughs, urban districts and rural districts) that first notified (leading edge, LE; graph A) and last notified (following edge, FE; graph B) cases of poliomyelitis in the epidemic year of 1947 (heavy line trace) and in the corresponding weeks of the four non-epidemic years of 1944–46 and 1948.