Introduction

The seasonal burden of infections that affects many communities in developing countries has been recognised for many years by agricultural economists and health professionals. Disastrous epidemics of malaria were clearly described in different regions of India during the last century (Christophers, 1911). The extent of the population who became sick was so great that agricultural production was decreased. Moreover, so many were sick that transport and sale of food was limited. Food intakes decreased and famines developed. Similarly, populations afflicted by guinea worm showed seasonal patterns of infection of the large joints with profound effects upon the ability to farm. In both infections the health of entire populations was critically affected by the onset of rains that controlled rates of transmission of the parasites.

Health professionals in many communities have also noted striking differences in patterns of disease between seasons. These may be so noticeable that supplies and staffing arrangements are modified accordingly (Tomkins, 1981). The dramatic increase in cerebro-spinal meningitis during the dry seasons is sometimes so great that hospital wards become grossly overcrowded, necessitating the stockpiling of antibiotics and the erection of tents for temporary accommodation. The outbreaks of diarrhoeal disease, especially during the rainy season, require adequate supplies of oral rehydration salts and additional staff for care of adults and children with severe dehydrating diarrhoeal diseases such as cholera. Diarrhoeal treatment units are often full during the rainy season, numbers of admissions decreasing during the dry season.