The implications of the Keystone virus-Aedes atlanticus transmission cycle are explored in the context of a quantitative model. Among the variables considered are the vertical transmission rate, the effect of the virus upon vector fertility and survival, vector densities and distributions, the proportion susceptible in the vertebrate population, the attractiveness of different vertebrates to the vector and vector survival rates. The logical relationships between these several variables are explored. It is concluded that the current view of Keystone virus maintenance is quantitatively feasible, and that certain predictions may be made as to the magnitude of several parameters which have not yet been measured. Such predictions allow direct testing of the model. The general structure of the model is such that it may prove useful in describing the epidemiology of other vector-borne infections in which vertical transmission is essential for infection maintenance at certain periods of the year.
Present address: Ross Institute, School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, England.
Present address: Division of Communicable Diseases and Immunology, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D.C. 20012.