This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'Epstein-Barr virus (EBV) VCA-IgG 1 :80 and EBV antibody to early antigen EA1 :320 suggest which one of the following diseases? \nSelect and explain. \nA. Chronic infectious mononucleosis, B. Primary syphilis, C. Scarlet fever, D. Primary atypical pneumonia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Infectious mononucleosis (IM) may be suspected clinically but it is confirmed serologically. The heterophil antibody test, however, may be negative in up to 15% of adults and 35 to 40% of children. Because IM is caused by Epstein-Barr virus (EBV), a specific test for viral capsid antigen (VCA) of EBV is indicated when heterophil tests are negative. Acute IM is characterized by a VCA-IgM titer, and no VCA-IgG antibody or EBNA. Chronic EBV disease causes elevated VCA-IgG titers as well as high EA antibody titers.', 'role': 'assistant'}]