[How valid is the official data from the Health Department on reported morbidity in Israel? Hepatitis A as an example].

Hepatitis A is one of the most frequently reported notifiable infectious diseases in Israel. The annual incidence as reported is around 70/100,000. The physician or the diagnostic laboratory notifies the district health office of the Ministry of Health. The purpose of this research was to evaluate the sensitivity of passive surveillance of hepatitis A morbidity among adults, 18 years and over. Methods included study of notifications to the Ministry of Health or hospitalizations of cases of hepatitis A and of positive laboratory tests results (IgM) for hepatitis A. We estimated the extent of under-reporting by 2 different methods of extrapolation. Data based on passive surveillance among the adult population, between 1.1.1993-31.12.1994, comprised less than 1/5 of the actual number of cases. Physicians notified about 6.2% of their hepatitis A patients. 5.1% of the notifications to the district health office were sent twice or more, usually both by the physicians and labs. The official data on hepatitis A morbidity, based on passive surveillance, are considerably underestimated. Physicians and public health officials should be aware that such data may not accurately reflect the magnitude of the risk or the amount of disease that can be prevented. Efforts should be made to improve this situation.