Seroprevalence of Coxiella burnetii infection in southern Taiwan.
The emergence of infection with Coxiella burnetii, the causative organism of Q fever, has been only recently recognized in Taiwan. Several cases of acute Q fever infection have been described, but the prevalence of antibodies to C. burnetii in the general population in Taiwan has not been reported. Thus, we studied the seroprevalence of C. burnetii infection in southern Taiwan. We conducted a retrospective serosurvey to examine the prevalence of C. burnetii infection among subjects admitted to a rural hospital in Taiwan for various reasons, and among presumably healthy attendees of a routine physical examination clinic of an urban public hospital. The diagnosis of C. burnetii infection required the presence of antibodies to both phase I and II antigens (titer > or = 1:16) or only to phase II antigens (titer > or = 1:256), as detected by indirect immunofluorescence assay. The prevalence of C. burnetii infection was 4.2% in both the in-patient (15/357) and physical examination participant (11/259) populations. None of these subjects had signs compatible with acute Q fever (febrile illness within the past 3 months). The antibody prevalence rate was higher in males than in females, and peaked in persons aged 61 to 70 years. These data suggest that C. burnetii infection is not rare in southern Taiwan and does not cause clinical symptoms in all infected patients.