Viral hepatitis in Israel: the effect of canvassing physicians on notifications and the apparent epidemiological pattern.

Notifications of morbidity are frequently incomplete but they represent the only practicable way of carrying out large-scale surveillance. Studies of hepatitis in the Central District of Israel offered an opportunity of assessing the reliability of routine data. The regular canvassing of physicians resulted in a 2-3-fold increase in reports of viral hepatitis. Comparisons of rates before and after canvassing with those for an insured population within the Central District indicated that there was an improvement from 37.4% in 1960/61 to 96.2% in 1968/69. None the less, the lower (precanvassing) level of reporting adequately delineated year-to-year fluctuations in morbidity, the seasonal cycle, and age distribution. One consequence of canvassing was a distortion of the secular trend not only for hepatitis but also for some other communicable diseases.