This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable Diseases, Subject name: Social & Preventive Medicine
Epidemiological markers of Hepatitis - B is 
Select and explain. 
A. HBs Ag, B. Anti - HBs, C. Anti HBc, D. HBe Ag
A: HBs Ag
Answer: A: HBs Ag 
Explanation: (HBsAg) (177- Park 19th) (188-Park 20th) (563-Chakraborthy-Micro 2nd)HBsAg. Types are useful markers of epidemiology. These are eight antigenic types of HBs Ag* HBsAg - appearance of HBs Ag is the First evidence of infection, appearing before biochemical evidence of liver disease and persists throughout the clinical illness* Anti HBs Ag - signals recovery from HBV infection, noninfectivity and immunity* HBeAg - indicates viral replication and infectivity