Which marker indicates current Hep B infection status?

• A. Anti-HBs
• B. Anti-HBc
• C. HBsAg
• D. HBeAg

Answer: (C)

Detectable surface antigen of the hepatitis B virus signals an active infection. When someone is currently infected, the virus produces HBsAg in the blood, appearing early after exposure and, if the infection becomes chronic, persisting for months or years. This marker is used clinically to determine ongoing infection and potential contagiousness. In contrast, anti-HBs indicates immunity from vaccination or recovery, anti-HBc shows prior exposure (with IgM anti-HBc pointing to an acute infection and total anti-HBc indicating past exposure), and HBeAg reflects high viral replication and infectivity but does not by itself define current infection status. Therefore, the presence of HBsAg best indicates an ongoing hepatitis B infection.