Which hepatitis B serology marker indicates current infection?

Which hepatitis B serology marker indicates current infection?

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

Answer: (A)

In hepatitis B serology, active viral replication in the blood—i.e., current infection—is indicated by the presence of the surface antigen, HBsAg. This marker appears early in infection and can be seen in both acute and chronic hepatitis B. If it persists for more than about six months, the infection is considered chronic. When someone clears the virus or has immunity from vaccination, HBsAg disappears and anti-HBs appears, signaling protection rather than ongoing infection. Other markers tell different stories: anti-HBs shows immunity (from vaccination or recovery), anti-HBc indicates exposure to the virus (with IgM suggesting a recent infection and IgG indicating past infection), and anti-HBe points to lower viral replication and reduced infectivity but does not by itself confirm current infection. Therefore, the marker that indicates current infection is HBsAg.

In hepatitis B serology, active viral replication in the blood—i.e., current infection—is indicated by the presence of the surface antigen, HBsAg. This marker appears early in infection and can be seen in both acute and chronic hepatitis B. If it persists for more than about six months, the infection is considered chronic. When someone clears the virus or has immunity from vaccination, HBsAg disappears and anti-HBs appears, signaling protection rather than ongoing infection.

Other markers tell different stories: anti-HBs shows immunity (from vaccination or recovery), anti-HBc indicates exposure to the virus (with IgM suggesting a recent infection and IgG indicating past infection), and anti-HBe points to lower viral replication and reduced infectivity but does not by itself confirm current infection. Therefore, the marker that indicates current infection is HBsAg.