often are not fully aware of reporting requirements in connection with other reportable diseases and do not initiate reports routinely (Allen and Ferson, 2000). In addition, some persons with chronic HBV infection can experience sudden increases in alanine aminotransferase (ALT) that may be associated with jaundice or liver decompensation. That change may have a variety of causes, including infection with another hepatitis virus; alcohol, drug, or medication use; or sudden hepatitis B disease reactivation that can be associated with the period of seroconversion from a hepatitis B e antigen (HBeAg) state to an antibody to hepatitis B e (anti-HBe) state or reversion from an anti-HBe state back to an HBeAg-positive state (Koff, 2004). Therefore, in investigating acute symptomatic infections, it is important to identify outbreaks so that preventive measures can be undertaken and, in the case of hepatitis B, to identify and screen close contacts who might benefit from the hepatitis B vaccine. Such information is needed if surveillance staff is to determine which cases are newly diagnosed, the result of recent exposure, or chronic (Fleming et al., 2006).

Classifying acute cases of hepatitis B and hepatitis C requires a complex integration of clinical data, positive and negative laboratory data, and prior or repeat testing (see Boxes 2-2 and 2-3). Many of the test results—for