Epidemiological features of epidemic cholera (El Tor) in Zimbabwe

Epidemics of cholera have been frequent in southern Africa since the reintroduction of the disease to the continent in 1970. In late 1992, following a severe drought and an influx of refugees from Mozambique, cholera reappeared in Zimbabwe for the first time since 1985 and rapidly spread through the rural areas of the country. Data relating to symptomatic cholera infection collected during 2 large outbreaks on the eastern border of the country showed that host age and sex were important factors relating to symptomatic infection, as were population density and access to water. Epidemic profiles for the 2 study areas differed in that one of the profiles exhibited a distinct second phase epidemic. This unusual pattern was compared qualitatively with the output of a series of simple mathematical models to examine the contribution of different epidemiological processes to the pattern of disease observed. Model output suggested a complex disease process, in which the dynamics may have been influenced by spatial components. Statistical analysis of these unusual data showed that the observed pattern was independent of the effects of host age or sex, and provided compelling evidence of a marked spatial component of the second phase epidemic.