This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Hepatitis B infectivity is indicated by: 
Select and explain. 
A. Anti-HBsAg, B. HBsAg + HBeAg, C. Anti-HBsAg - Anti-HBc, D. Anti-HBeAg + Anti-Hbs Ag
B: HBsAg + HBeAg
Answer: B: HBsAg + HBeAg 
Explanation: Answer is B (HBs Ag + HBe Ag) HBe Ag: Its principal clinical usefulness is an indicator of relative infectivity - Harrison HBs Ag: Its presence in serum indicates infection /pervious vaccination with hepatitis B virus. HBs Ag Anti- HBsAg Anti Hbe HBe Ag Anti-Hbe Acute HBV infection High infectivit - IgM + - Chronic HBV infection High infectivity + - IgG + - Thus, the presence of the above two markers indicate an infection with hepatitis B virus and high infectivity. Q Whether the infection is acute or chronic can, however, only be commented if status of anti-HBe marker is dear.