ObjectiveTo assess the occurrence of active human cytomegalovirus (HCMV) infection and HCMV disease and to evaluate potential risk factors in immunocompetent intensive care patients after major surgery or trauma.DesignA prospective clinical study.SettingAn anesthesiological intensive care unit (ICU) in a university hospital.PatientsFifty-six anti-HCMV immunoglobulin G (IgG) seropositive patients without manifest immunodeficiency whose simplified acute physiology score (SAPS II) value rose to ≥41 points during their ICU stay.InterventionsOnce a week, the patients were examined for active HCMV infection by polymerase chain reaction and by viral cultures from blood and lower respiratory tract secretions. Three times a week, detailed clinical examination for signs of HCMV disease was carried out.Measurements and Main ResultsTwenty of the 56 ICU patients (35.6%) who met the study criteria of a SAPS II score >40 points and anti-HCMV IgG seropositivity developed an active HCMV infection as diagnosed by the detection of HCMV DNA in leukocytes, plasma, or respiratory tract secretions. In seven patients, the virus was isolated in the respiratory tract secretions. Severe HCMV disease appeared in two patients with pneumonia or encephalitis respectively. In patients with active HCMV infection, the mortality tended to be higher (55%) than in those without (36%); the duration of intensive care treatment of the survivors was significantly longer in the patients with active HCMV infection (median 30 vs. 23 days;p= .0375). Univariate testing for factors associated with active HCMV infection showed the importance of sepsis at admission (p= .011) and prolonged pretreatment on the ward or in an external ICU (p= .002); the relevance of underlying malignant disease was borderline (p= .059). Multiple regression analysis identified only sepsis to be independently associated with active HCMV infection (p= .02; odds ratio, 4.62).ConclusionsEven in a group of ICU patients without manifest immunodeficit who were anti-HCMV IgG seropositive and had reached a SAPS II score of ≥41 points, active HCMV infection occurred frequently (35.6%). Septic patients were affected twice as often as the total study population. In 2 of the 20 cases, active HCMV infection progressed to severe HCMV disease. Proper diagnosis demands special clinical attention combined with extended virological examinations. Further studies in a larger patient group should evaluate the influence of HCMV on ICU mortality.