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Epidemiology of Virus Hepatitis

EPIDEMIOLOGY OF VIRUS HEPATITIS Infective hepatitis belongs to that small but important group of infectious diseases which from time to time burst with almost explosive violence into epidemics of pandemic proportions. Unlikeother diseases showing this epidemiological peculiarity, such as influenza, great increase in its incidence is fortunately not associated with any obvious increase in virulence, and the mortality rate, in the economically superior communities at least, rarely exceeds 0.2%. It may, however, apart from more persistent sequelae, incapacitate patients for weeks or months, and in the second world war it seriously affected the strategy of both the contending armies, especially in the Mediterranean theatre. Moreover, among peoples already weakened by poverty, malnutrition, and disease, epidemic hepatitis may levy a much higher toll. Recent experience teaches quite clearly that war, especially world war, creates the ideal situation for widespread dissemination of this viral disease. This is clearly shown in Sir John McNee's Harveian Lecture, published in the opening pages of this issue. As he rightly points out, the many possible causes of epidemics of jaundice-including Weil's disease, malaria, dysentery, and the enteric groups of fevers-could not be clearly differentiated before the development of the science of bacteriology. It is therefore difficult to assign to its precise aetiological agent any epidemic prior to the bacteriological era. But because of the low mortality of viral hepatitis it is possible to distinguish fairly readily epidemics of viral jaundice from those due to other agents. In the epidemic among the troops in the American Civil War 161 deaths were reported amongst 22,509 cases-that is, a fatality rate of 0.7% -and in the South African War a similarly low fatality rate was recorded amongst 5,648 cases. In the first world war also the outbreaks in Mesopotamia claimed only 46 lives out of over 6,000 cases, and in the war of 1939-45 the fatality rate among the Allied troops was about 1 in 500. Serious epidemics of viral jaundice are rare apart from war, but isolated cases and small outbreaks were common throughout Europe between the two wars. Such outbreaks provided opportunity for important studies in epidemiology' and appeared to show that the disease was spread by infected droplets among close contacts. But studies on the spread of infection among the troops, and the experiments on transmission to human volunteers, show that the infecting agent is much more readily recoverable