Which combination of hepatitis B serologic markers indicates a highly infectious stage?

Which combination of hepatitis B serologic markers indicates a highly infectious stage?

• A. HBsAg positive and HBeAg positive
• B. HBsAg negative and anti-HBs positive
• C. Anti-HBc positive and anti-HBe positive
• D. HBeAg negative and anti-HBs negative

Answer: (A)

The key idea is that infectiousness in hepatitis B closely tracks viral replication, which is signaled by HBeAg. HBsAg shows that a person has an active infection, while HBeAg indicates the virus is replicating vigorously and producing many viral particles. When both are present, there is ongoing, high-level replication, making the person highly contagious. If HBsAg is present but HBeAg is absent, replication is typically lower, so infectivity is reduced. If the person has anti-HBs, that means immunity (via vaccination or recovery), and they are not infectious. Anti-HBc alone shows prior exposure but doesn’t by itself confirm high infectivity. HBeAg negative with anti-HBe positive suggests reduced replication and lower infectivity. So the combination of HBsAg positive and HBeAg positive best indicates a highly infectious stage.

The key idea is that infectiousness in hepatitis B closely tracks viral replication, which is signaled by HBeAg. HBsAg shows that a person has an active infection, while HBeAg indicates the virus is replicating vigorously and producing many viral particles. When both are present, there is ongoing, high-level replication, making the person highly contagious.

If HBsAg is present but HBeAg is absent, replication is typically lower, so infectivity is reduced. If the person has anti-HBs, that means immunity (via vaccination or recovery), and they are not infectious. Anti-HBc alone shows prior exposure but doesn’t by itself confirm high infectivity. HBeAg negative with anti-HBe positive suggests reduced replication and lower infectivity. So the combination of HBsAg positive and HBeAg positive best indicates a highly infectious stage.