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

All clinicians and nurses who participated in this study were trained on the study protocol and sample collection. A clinician examined the patients and invited them to participate in the study if they met the eligibility criteria. In particular for the AUFs, all the patients were screened for dengue infection by RDTs, and the patients who came from a malaria endemic area were screened using a peripheral blood smear. Accordingly, only AUF patients who were negative for these diseases were included in this study. After obtaining written informed consent from the participants, the clinicians recorded their vital signs, signs and symptoms of the current illness, their history of exposure to the forest within 30 days, chronic comorbidity diseases and basic clinical laboratory results on a case report form (CRF). A nurse collected a total of 3 mL of whole blood, divided into 1 mL of whole blood in an EDTA tube and approximately 1 mL of plasma in a dry tube after centrifugation, and 1 mL of urine from each participant. One throat swab specimen was taken by a clinician and preserved immediately into a viral transport medium. The clinician also collected eschar swab specimens if the patient presented with one or several eschars based on a previously described method [26] . In addition, from each patient with AUF, we collected 1 mL of plasma in the convalescent phase, which occurred 7-10 days after the first plasma collection. All the specimens were immediately preserved at −20°C at the hospitals in Quang Nam province (Vietnam) until analysis at the University Hospital Institute Méditerranée Infection, Marseille (France).