Further work on forecasting smallpox epidemics in India and British tropical countries based on previous climatic data

Abstract

1. Earlier work on forecasting epidemics of smallpox in India, based on the study of the previous rainfall and humidity, has been confirmed and extended by the present study and a few instances which did not conform to the general rule have been explained as due to the spread of the disease from an adjacent province.2. An extension of the inquiry to other tropical countries of the British Empire indicates that in tropical countries in general with well-marked dry and wet seasons, the annual decline of smallpox incidence to a low minimum in relation to high absolute humidities during the rainy season is the rule; for it is absent in equatorial Uganda with rains throughout the year, and both the monsoon period and the monthly incidence of smallpox are reversed in such a Southern Hemisphere country as Nyassaland in accordance with the general rule.3. Where smallpox is endemic in such countries increased prevalence in any year may usually be foreseen by watching the meteorological records in time to control the expected increase to some extent by increased use of vaccination.4. Other air-borne diseases are worthy of study on similar lines in countries with suitable vital statistics and climatic conditions.