Hepatitis Surveillance

The total numbers of cases reported to the Viral Hepatitis Surveillance Program (VHSP) are shown in Table 1A. Approximately 36% of hepatitis A cases, 26% of hepatitis B cases, and 18% of NANB hepatitis cases reported to the NNDSS in 1993 were also reported to the VHSP. These percentages reflect a substantial decline in reporting to the VHSP. Reporting to the VHSP remains inconsistent among states, with increasing numbers of states reporting fewer of their NNDSS cases to the VHSP than in previous years (Table 1B). In 1987, six states reported to VHSP less than 15% of their NNDSS cases; in 1993, this trend increased to 12 states.

The agreement between reporting to the NNDSS and to the VHSP does not necessarily measure the completeness of reporting from a particular state, since not all cases may be reported to the NNDSS and the two systems have different reporting criteria. The increasing discrepancy between the two systems has resulted in differences in the relative proportions of types of viral hepatitis reported. Before 1990, the proportions of reported cases by type were similar between the two surveillance systems. Since then, the proportion of hepatitis cases reported as hepatitis A to the two systems have remained similar, but the proportion of cases reported as hepatitis B have been discrepant: 24% to 27% of the total VHSP cases were reported as hepatitis B, compared with 35% to 38% of total cases reported to NNDSS. The VHSP also received reports on smaller proportions of the total number of NANB hepatitis cases (7% to 8% of total cases) than did NNDSS (up to 13% of total cases).

These differences in proportions of cases are partly due to the fact that VHSP excludes cases that do not meet the case definition (VHSP eliminated 15% of reported cases as non-cases in 1993). In addition, because of strict adherence to the case definition, VHSP classified a larger proportion of reported cases as nonspecific hepatitis: 15% of cases were classified as hepatitis unspecified by the VHSP during 1993 compared with 1.5% of cases reported to NNDSS. Beginning with data collected in 1995, hepatitis cases that have type unspecified are no longer requested or printed in the MMWR.

The VHSP excludes reported cases that do not meet the case definition for acute viral hepatitis (see "Case Definition" section), including cases that seem to be due to chronic infections. Some responses to the VHSP questionnaires are incomplete, and the information is insufficient to verify the case as an acute infection, or to confirm the serologic type of hepatitis, even though partial testing may have been done. Cases may also be reported too late to be included in the analysis. The latest date for submitting case reports to the VHSP for the calendar year is March 31 of the following year.