Influence of Human T Lymphotropic Virus Type I Infection on the Etiology of Community-acquired Pneumonia

BACKGROUND: Human T lymphotropic virus type I (HTLV-I), the cause of human T cell leukemia, is associated with a high incidence of several other infectious diseases. However, the relationship between pulmonary infections and HTLV-I infection is still unclear. OBJECTIVE: A large-scale retrospective study was conducted on hospital inpatients to evaluate the relationship between community-acquired pneumonia (CAP) and HTLV-I infection. METHODS: The present study included 4,666 hospitalized patients during 1991-2007. Three hundred and thirteen of them were diagnosed as CAP. The presence of serum HTLV-I antibody was determined in all patients on admission. Prevalence of HTLV-I infection was analyzed between CAP patients and all inpatients. We also compared HTLV-I-positive CAP patients and HTLV-I-negative CAP patients for severity and manifestation of pneumonia. RESULTS: The prevalence of HTLV-I was higher in CAP patients than in all inpatients (18.9%: 13.7%, p=0.011). The rates of renal diseases and collagen vascular disorders were higher in the HTLV-I-positive CAP patients than in the HTLV-I-negative CAP patients. Multivariate analysis revealed that HTLV-I infection, gender, COPD and collagen vascular disorders were all independent risk factors for CAP. The severity indices of CAP, the PORT score and the CURB-65 score, were higher in the HTLV-I-positive patients than in the HTLV-I-negative patients. CONCLUSION: This study demonstrates that HTLV-I infection might be an independent risk factor for CAP and that HTLV-I-infected patients tend to demonstrate a relatively severe form of pneumonia.