Some observations on the ecology of infectious hepatitis.

Analysis of reported rates for infectious hepatitis in the USA and in New York State for the years 1954 through 1962 reveals an inverse relationship between incidence and population density in epidemic as well as inter-epidemic periods. Patterns of age-specific rates were also found to vary with population density, the fluctuations being much greater in rural than in urban areas. The gradual change of hepatitis from a predominantly childhood to an adult disease is noted in data from California.The observations based on data from the USA are compared with those for Denmark and contrasted with recently reported studies from eastern Europe. Such comparisons may prove of value in predicting patterns to be anticipated in areas where infectious hepatitis is currently in the early or pre-epidemic stage of its evolution as a public health problem.