The present report describes a different approach to the study of the natural history of infectious hepatitis in the general population. Previous investigations have been confined to local circumscribed epidemic situations in the community or to “closed” populations, e.g., institutions or military establishments.
For a period of 2 years all cases in the three counties comprising the study area were followed with an initial and 40-day follow-up visit to each household. The illnesses occurring in households were examined and the history of gamma globulin prophylaxis was obtained for contacts not ill. These data made possible evaluation of the efficacy of gamma globulin and a description of certain elements in the epidemiology of infectious hepatitis in the 5,434 persons included in the study.
The study deals for the most part with infectious hepatitis as an endemic disease with cases occurring in every age group in all seasons of the year and in all sorts of household groups. The 1,546 cases are divided on the basis of clinical data into “confirmed” infectious hepatitis and “probable” infectious hepatitis. All but 129 cases fall into the first category. The chief difference in the age distribution was a marked skewness to younger age groups in the “probable” diagnostic category.
Age specific attack rates were calculated and appeared to be biphasic in nature. Young adults seemed to be at as high a risk as those in the younger age groups.
Secondary attack rates in 1,160 households are presented and appear to be consistently lower than those reported in the literature. This difference could be related to a number of factors; definition of secondary cases and the fact that 40% of the household population studied received prophylactic gamma globulin are probably the most significant factors.
Attack rates of 2% of the gamma globulin protected group contrast sharply with rates of 18% in those with no prophylaxis.
Three hundred sixty-six or 24.9% of the patients had residual findings. Of these 24.9%, 12.6% appeared to have “probable” continuing liver damage and 12.3% had other less severe residuals. Three and seven-tenths per cent of the cases terminated fatally.
Present address: U. S. Navy Preventive Medicine Unit No. 2, Norfolk Base, Norfolk, Virginia.