RECURRENT OUTBREAKS OF MEASLES, CHICKENPOX AND MUMPS

Abstract

The mean monthly contact rates for measles, chickenpox and mumps estimated from the monthly reported cases show systematic differences between the years with many cases and the years with few cases. In New York City, the mean contact rates for chickenpox were different during the years 1931–1945 than during 1946–1960. The clustering of cases within social groups is proposed to account for these differences in the contact rates and for other empirical observations. The irregularity of outbreaks of measles in cities of fewer than two million people can be explained by stochastic effects. Outbreaks of measles in distant large metropolitan areas are highly correlated in time, but the reasons for the correlation are not clear.