Which serologic marker indicates an acute Hepatitis B infection?

The serologic marker that indicates an acute Hepatitis B infection is the presence of Anti-HB core IgM. This antibody is the first indicator of an acute infection, as it appears during the early stages of the disease when the body is actively responding to the Hepatitis B virus. Anti-HB core IgM indicates that the patient is either in the acute phase of infection or has recently been infected.

The other options represent different stages of infection or immune response. For example, Anti-HB surface IgG would indicate a resolved infection or chronic infection, as it signifies that the immune system has produced antibodies against the hepatitis B surface antigen. HB surface antigen is present in acute and chronic infections, but it does not specifically indicate that the infection is acute. Lastly, HB e antigen is associated with active viral replication and higher transmissibility but does not specifically mark acute infection; it can be seen in both acute and chronic cases. Thus, the presence of Anti-HB core IgM is the most crucial and specific marker for diagnosing an acute Hepatitis B infection.