Population mixing and the incidence of childhood leukaemias: retrospective comparison in rural areas of New Zealand: Fig 1

In 1988 Kinlen hypothesised that childhood leukaemia occurs as a rare response to a common infection and that population influxes into rural areas with higher proportions of susceptible individuals favour epidemics of the infection and increases in the incidence of leukaemia.1 Most ecological studies of childhood leukaemia in relation to this issue have supported the hypothesis.2 Our study was conducted to test whether population influxes into rural areas of New Zealand were associated with increases in the incidence of childhood leukaemias. Forestry developments, including the building of a pulp and paper mill, occurred in the adjacent Rotorua, Matamata, and Whakatane areas of New Zealand's North Island in the 1950s. These developments led to population growth and the establishment of the new towns of Kawerau and Murupara. In this study boundaries were defined for the Rotorua, Matamata, and …