The following is a marker of acute hepatitis B infection:
**Core Concept**
Acute hepatitis B infection is marked by the presence of **HBsAg (hepatitis B surface antigen)** and **IgM anti-HBc (IgM antibody against hepatitis B core antigen)**. HBsAg appears first during acute infection, while IgM anti-HBc indicates recent infection and distinguishes it from chronic or resolved cases.
**Why the Correct Answer is Right**
HBsAg is the earliest detectable serological marker in acute hepatitis B, appearing 1β2 weeks after exposure. IgM anti-HBc develops concurrently and peaks during the acute phase, declining as IgG anti-HBc becomes dominant in chronic or resolved infections. Together, they confirm active viral replication and acute disease onset.
**Why Each Wrong Option is Incorrect**
**Option A:** *HBeAg* indicates high viral replication but is not specific to acute infection; it is also seen in chronic HBV.
**Option B:** *Anti-HBs* (antibody to surface antigen) arises after recovery or vaccination, not during acute infection.
**Option C:** *HBc IgG* persists long-term in both resolved and chronic infections, lacking specificity for acute disease.
**Option D:** *HBV DNA* is present in both acute and chronic phases, so it cannot differentiate between them.
**Clinical Pearl / High-Yield Fact**
Remember: **"IgM anti-HBc is the hallmark of acute hepatitis B."** If IgM anti-HBc is absent in a