Technical Notes

Case Ascertainment and Case Reporting

For health department staff to report cases of viral hepatitis to CDC, systems and processes must be in place that ensure each case is reported. Because of varying state laws, resources, and infrastructure, not all health departments report all cases of perinatal, acute, or chronic viral hepatitis to CDC. Additionally, diagnosing every acute case is impossible, because symptoms might be either so mild that the person does not seek care or too vague to prompt a health care provider to suspect and test for viral hepatitis.

Case reporting begins when a local or state health department receives a positive laboratory report, indicating a person has a viral hepatitis infection. Because initial reporting provides limited information and additional laboratory test results or clinical symptoms are frequently needed for classifying cases, reported cases might require extensive follow-up to obtain full information for establishing case status and case classification.

During 2020, only 14 states (Florida, Georgia, Indiana, Kentucky, Louisiana, Massachusetts, New Jersey, North Carolina, Oklahoma, Ohio, Tennessee, Utah, Washington, and West Virginia) received federal funding to support viral hepatitis surveillance. Health departments prioritize cases for follow-up using their own protocols and might submit cases to CDC with incomplete or missing information.

Additionally, the volume of laboratory reports for viral hepatitis infections might be so large that not all health departments are able to consistently detect and report all chronic cases to CDC. Data regarding chronic hepatitis B and hepatitis C infections are included in this report where available; however, these are newly identified chronic viral hepatitis cases and do not measure prevalence.

Finally, many staff in health departments were reassigned to work on the COVID-19 pandemic during 2020, which will have affected a health department’s ability to investigate and report viral hepatitis cases in its jurisdiction.

All viral hepatitis conditions with no reported cases or characterized as Not Reportable or Data Unavailable for 2020 in a jurisdiction’s final signed report to CDC’s National Center for Surveillance, Epidemiology, and Laboratory Services (CSELS) were reported according to the following notation used by CSELS¹:

• —: No reported cases. The reporting jurisdiction did not submit any cases to CDC.
• N: Not reportable. The disease or condition was not reportable by law, statute, or regulation in the reporting jurisdiction.
• U: Unavailable. The data are unavailable.

Summary of state or jurisdiction reporting exceptions for viral hepatitis surveillance*, 2020

Notes:

• Perinatal hepatitis B and hepatitis C are not included in this table
• n/a = no state/jurisdiction had the reporting exception

Urbanicity: Urban and rural categorization was made according to CDC’s 2013 National Center for Health Statistics urban-rural classification scheme for counties and county-equivalent entities. Large central metropolitan, large fringe metropolitan, medium metropolitan, and small metropolitan counties were grouped as urban. Micropolitan and noncore counties were grouped as rural.

US Department of Health and Human Services regions provide a standardized structure for grouping jurisdictions into larger geographic areas. Ten regional offices directly serve state and local organizations.

US Department of Health and Human Services regions

*US territories are not included in this report.

Case Definitions

To ensure consistent reporting across states, the Council for State and Territorial Epidemiologists, in collaboration with CDC, developed case definitions for viral hepatitis A, hepatitis B, and hepatitis C.

The case definitions facilitate standardized reporting by using uniform criteria and differentiating between acute, chronic, and perinatal cases. When new technologies are developed for laboratory testing or better clinical data become available, the case definitions are updated.

Changes in case definitions should be considered when examining temporal trends. For more information regarding the case definitions used in 2020, visit the National Notifiable Diseases Surveillance System’s website.

In 2020, new case definitions for acute and chronic hepatitis C were implemented. As outlined in the Council of State and Territorial Epidemiologists (CSTE) hepatitis C Position Statement², the 2020 acute hepatitis C case definition was developed to emphasize more objective laboratory tests and reduce dependence on subjective and non-specific signs and symptoms. The change minimizes variability of practice in case classification among jurisdictions and was expected to increase the number of cases classified as acute hepatitis C relative to the 2016 hepatitis C case definition.

The impact of this new hepatitis C case definition on surveillance data is under evaluation; however, it is expected the magnitude of the increase in acute hepatitis C cases reported will not be uniform across all jurisdictions.  It will likely vary by factors such as the types of positive and negative hepatitis laboratory results and liver function tests (i.e., alanine transaminase (ALT) and total bilirubin) that are reportable by law or mandated in the jurisdiction, and their capacity to investigate and conduct case investigations.

Estimating Incidence of Acute Viral Hepatitis

To account for underascertainment and underreporting, a probabilistic model for estimating the true incidence of acute hepatitis A, hepatitis B, and hepatitis C from reported cases has been published previously (6). The model includes the probabilities of symptoms, referral to care and treatment, and rates of reporting to local and state health departments. The published multipliers have since been corrected by CDC to indicate that each reported case of acute hepatitis A represents 2.0 estimated infections (95% bootstrap CI: 1.4–2.2); each reported case of acute hepatitis B represents 6.5 estimated infections (95% bootstrap CI: 3.7–15.9); and each reported case of acute hepatitis C represents 13.9 estimated infections (95% bootstrap CI: 11.0–47.4). This model has not been recalibrated to account for the change in the acute hepatitis C case definition that occurred in 2020, and as such, estimated infections of acute hepatitis C generated for 2020 may require revision in the future. Work is underway to update the multipliers for hepatitis A, hepatitis B, and hepatitis C using updated literature.

Mortality Surveillance

The NVSS provides information regarding deaths that occur in the United States. NVSS data in this report are from the 2016–2020 Multiple Cause of Death files in the CDC WONDER online database³. These data are based on information from all death certificates filed in the vital records offices of the 50 states and the District of Columbia through the Vital Statistics Cooperative Program. Deaths of nonresidents (e.g., nonresident aliens, nationals living abroad, or residents of US territories) and fetal deaths are excluded.

Perinatal Hepatitis B Prevention Program Surveillance

Outcome data for infants born to a gestational parent with HBV infection are reported by the CDC Perinatal Hepatitis B Prevention Program. This program funds 64 jurisdictions to identify pregnant persons infected with HBV and to case-manage their infants to improve receipt of postexposure prophylaxis, hepatitis B vaccine series completion, and post-vaccination serologic testing. Data in this report are from the reporting period for the 2019 birth cohort, followed from January 1, 2019, through December 31, 2020, and only includes infants managed by the program. Infants have variable lengths of follow-up time, depending on their date of birth. More information is available at the Perinatal Hepatitis B Prevention Program website.