Frequent double infection with Epstein-Barr virus and human herpesvirus-6 in patients with acute infectious mononucleosis.

Clinical infectious mononucleosis (IM) represents a benign self-limited form of lymphoproliferative disease which is usually caused by infection with Epstein-Barr virus (EBV). Microscopic characteristics of this lymphoproliferative disorder, however, are not ultimately specific for EBV infection, but can also be seen in infections with other lymphotropic viruses, especially of the herpesvirus family. Human herpesvirus-6 (HHV-6) infection can apparently be associated with a number of diseases also seen in EBV infection. Also, postinfectious chronic fatigue syndrome (PICFS) which may follow IM is in more than 60% of the cases accompanied by persistent active HHV-6 infection. We thus screened serologically 215 cases of acute IM for evidence for infection with EBV, HHV-6 and CMN. Patients were tentatively grouped into those having primary infection or reactivated (probably non-primary) infections. Cases were followed for two years to monitor changes in titers. Of all 215 cases, 211 (98.1%) were positive for EBV, 137 (63.7%) for primary infections, 21 (9.8%) for reactivated infection, and 53 (24.6%) for latent EBV. Thirty-three (15.3%) cases had primary HHV-6 infection, 63 (29.3%) active or reactivated HHV-6 infection, and 71 (33.9%) latent HHV-6. Double active EBV and HHV-6 infection, including primary and reactivated infections, amounted to 89 (39.5%) cases. Cytomegalovirus (CMV) antibody titers were found in 81 (37%) cases, 48 (22.3%) of which indicated latent infection and 33 (15.3%) active infection. Only two cases had evidence of active CMV infection alone, 1 cases of active CMV and HHV-6 infection. Serologic titers in 12 (5.6%) cases indicated combined active infection with CMV, EBV and HHV-6.(ABSTRACT TRUNCATED AT 250 WORDS)