Infection with human immunodeficiency virus does not influence the clinical severity of scrub typhus

Infection by Orientia (formerly Rickettsia) tsutsugamushi causes scrub typhus, a severe febrile disease common in Asia. Both scrub typhus and AIDS are prevalent in northern Thailand. Therefore, we prospectively investigated the impact of infection due to human immunodeficiency virus (HIV) on the severity of the clinical syndrome produced by O. tsutsugamushi. The severity of scrub typhus was objectively graded on admission of patients to the hospital, and serologies for antibodies to HIV were performed. Fourteen (16%) of 86 patients with scrub typhus were infected with HIV; the median T helper cell count was 70/mm3. There were no significant differences between HIV-infected patients and non-HIV-infected patients in severity scores or other admission characteristics. O. tsutsugamushi was isolated in blood samples from 48.6% of patients without HIV infection and in blood samples from 14.3% of HIV-infected patients (P < .05 x 2 test). The clinical manifestations of O. tsutsugamushi infection, unlike those due to some other intracellular pathogens, are not unusually severe in immunocompromised patients with AIDS.