<prompt> Epstein-Barr virus EBV VCA-IgG 1 :80 and EBV antibody to early antigen EA1 :320 suggest which one of the following diseases?Chronic infectious mononucleosisPrimary syphilisScarlet feverPrimary atypical pneumonia  <response>: 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. 