Reduce the rate of hepatitis A — IID‑10 Data Methodology and Measurement

Acute hepatitis A is a reportable disease in all states, the District of Columbia (DC), and New York City (CSTE query) and nationally notifiable (CDC NNDSS List of Notifiable Conditions, historically by year). The NNDSS is a nationwide collaboration that enables all levels of public health to share notifiable-disease-related health information. In some jurisdictions, viral hepatitis is a reportable disease: health care providers, hospitals, and laboratories are mandated to report cases to the state health department. In other jurisdictions, viral hepatitis is a notifiable disease, rendering such case reporting voluntary. Each state has its own laws and regulations defining whether viral hepatitis is reportable or notifiable. CDC in turn receives voluntary viral hepatitis case notification from each state or reporting jurisdiction. In 2016, all 50 states and DC submitted reports of hepatitis A to CDC (2016 Surveillance Summary). Surveillance for viral hepatitis through NNDSS is based on case definitions developed and approved by CSTE and CDC. Reported cases of hepatitis A are required to meet specific clinical and laboratory criteria. Only these confirmed cases are included in the numerator. Case rates per 100,000 US population are calculated based on the resident population of the United States for the data years and reporting states involved. For census years (e.g., 2010), population counts enumerated as of April 1 are used. For all other years, population estimates as of July 1 are used.

Limitations: Viral hepatitis is largely underreported in the NNDSS. Based on a simple probabilistic model for estimating the fraction of patients who would have been symptomatic, sought health care tests, and reported to health officials, actual hepatitis A cases are estimated to be 1.96 times the number reported to CDC (Klevens 2014). Additionally, rates may vary over time based on changes in public and provider awareness, changes in laboratory and diagnostic techniques, and changes in the definition of the condition (NPR).