"As part of CDC's [Centers for Disease Control and Prevention] National Notifiable Disease Surveillance System (NNDSS), viral hepatitis case-reports are received electronically from state health departments via CDC's National Electronic Telecommunications System for Surveillance (NETSS), a computerized public health surveillance system that provides CDC with data regarding cases of nationally notifiable diseases on a weekly basis. Although surveillance infrastructure is in place for reporting of acute infection, reports of chronic hepatitis B and C, which account for the greatest burden of disease, are not submitted by all states. As noted in a recent report from the Institute of Medicine, surveillance capacity to monitor both acute and chronic viral hepatitis is limited at the state and local levels, resulting in underreporting and incomplete variable quality data that is insufficient for understanding the magnitude of viral hepatitis. Data in this report should be interpreted with the consideration that reported cases of acute or chronic viral hepatitis represent only those relatively few infected persons who were detected, diagnosed, met a stringent case definition, and eventually reported to CDC in 2011. Because most acute and chronic infections are not reported, this Summary is mainly useful in detecting major trends in viral hepatitis A (HAV), B (HBV) and C (HCV). In 2011 and 2012 a major effort was undertaken to improve methodologies for estimating total number of new cases of hepatitis A, B and C from the number of cases reported for each disease. Estimates in this report of incidence of new infections were obtained using the newly improved methodology."
Centers for Disease Control and Prevention: https://www.cdc.gov/