<prompt> A nurse develops clinical symptoms consistent with hepatitis. She recalls sticking herself with a needle approximately 4 months before after drawing blood from a patient. Serologic tests for HBsAg, antibodies to HBsAg, and hepatitis A virus HAV are all negative; however, she is positive for IgM core antibody. The nurseDoes not have hepatitis BHas hepatitis AIs in the late stages of hepatitis B infectionIs in the window after the disappearance of HBsAg and before the appearance of anti-HBsAg  <response>: In a small number of patients with acute hepatitis B infection, HBsAg can never be detected. In others, HBsAg becomes negative before the onset of the disease or before the end of the clinical illness. In such patients with acute hepatitis, hepatitis B virus infection may only be established by the presence of antihepatitis B core IgM anti-HBc IgM, a rising titer of anti-HBc, or the subsequent appearance of anti-HBsAg Reference: Ananthanarayan and Paniker;s Textbook of Microbiology Tenth edition 