Serological Studies on Cytomegalovirus Infection in Relation to Infectious Mononucleosis and Similar Conditions

A study of a Swedish 3-year serum material from patients clinically suspeced of infectious mononucleosis (IM) revealed a 25% incidence of patients with typical Paul-Bunnell positive mononucleosis. Paul-Bunnell negative serum pairs were tested for antibodies against cytomegalovirus (CMV) antigen by complement-fixation, immunofluorescence and immunodiffusion. The occurrence of titer rises to CMV among Paul-Bunnell negative patients showed an incidence of 2.7% in 1966 and 4.6% in 1967–68. Approximately half of the CMV cases had low titers of mostly nonspecific sheep red cell agglutinins. Most patients in adult and old ages had demonstrable CMV antibodies in their sera; the curve relating age to frequency approached 90–100% in the highest age group (≥ 66 years), suggesting life-long persistence of antibodies to CMV.In a more detailed study on sera from patients with CMV antibody titer rises, immunofluorescence tests against Epstein-Barr virus (EBV) revealed concomitant titer changes against the two viruses in 2 or possibly 4 out of 11 cases. The possibility of double infections with CMV and EBV is discussed.