The epidemiological significance of islands

Abstract

Islands have proved fruitful laboratories for biogeographical research from Darwin and Wallace onwards. We examine here the significance of Black's work ( Journal of Theoretical Biology, 11, pp. 207–211 (1966)) on island epidemics. His original data on measles outbreaks on 19 islands over the 15 year period from 1949 to 1964 are reanalysed, and the confounding effects of island accessibility and population density upon estimates of the population threshold for measles endemicity are illustrated. Using later data, we extend Black's analysis into the post-1965 measles vaccination era both for the islands he studied and for 22 others, and then explore the potential of intra-island comparisons. Although Black confined himself to measles, this paper suggests that his ideas are extendable to a wide range of other infectious diseases. Island epidemiology has implications both for practical questions of disease control and for academic questions of the persistence and origin of diseases.