Prospective case-control analysis of the aetiologies of acute undifferentiated fever in Vietnam

Le-Viet, Nhiem; Le, Viet-Nho; Chung, Hai; Phan, Duc-Tuan; Phan, Quang-Duong; Cao, Thanh-Van; Abat, Cédric; Raoult, Didier; Parola, Philippe

Spotted fever group (SFG) rickettsial infections are not well known in Vietnam. A recent serosurvey found that 1.7% of the healthy population in northern Vietnam has antibodies against SFG rickettsiae (using R. conorii antigen, which is the agent of the tickborne Mediterranean spotted fever) [17] . In our study, R. felis was the only SFG rickettsia detected. R. felis infection has been identified as an emerging rickettsiosis worldwide and an important cause of AUF in sub-Saharan Africa [18, 19] . Fleas have been recognized as vectors of R. felis, but mosquitoes, such as Anopheles gambiae, the major vector of malaria, may also transmit this agent [19] . Few cases of this emerging infection have been identified in Asia [18] , and our three R. felis cases might be the first evidence of its existence in Vietnam. Because R. felis has also been detected in control afebrile patients in Africa [20] and in Asia, as in our study, further investigation is needed to precisely determine the role of R. felis in AUF in the tropics. Q fever caused by C. burnetii occurs worldwide, is most frequently acquired through the inhalation of contaminated aerosols or the consumption of milk, and has been identified as an important cause of AUF [21] [22] [23] . Although it has been reported in some countries surrounding Vietnam [24] , all our patients were negative for C. burnetii; therefore, we still do not have evidence of Q fever in Vietnam. Thus, this disease might exist with a very low prevalence, and further surveillance should be performed in the future.