Epidemiological features of sindbis fever in South Africa

Abstract

Background: In 2010,Martinique experienced a severe DENV-1 and DENV-4 coepidemic involving more than 10% of the population. A study was conducted in the Emergency Department (ED) to investigate the relationships between clinical severity of illness and virological characteristics. Methods & Materials: Dengue-like patients admitted within 8 days after the onset of fever were eligible. Data were recorded at presentation. Final outcome data were collected in all patients. Dengue cases were confirmed and serotyped by a hemi-nested RT-PCR. Dengue-specific antibodies were detected by using IgM capture, IgG capture, and IgG indirect enzyme linked immunosorbent assays. Basedondisease severity and thepatient caremethods, we distinguished three groups of clinical forms: uncomplicated forms treated at home with simple monitoring (G1), intermediate severity forms warranting intravenous rehydration in the ED and followed-up under ambulatory conditions (G2) and severe forms including DHF/DSS that most often warranted hospitalization (G3) Results: The study included 201 patients (107 females, median age 38 years, range 15-89). DENV-1 was demonstrated in 126 (63%) patients and DENV-4 in 75 (37%). Secondary infections were recorded more frequently in DENV-4 than in DENV-1 infections (64.5% versus 50%, respectively, p <0.001). Regarding clinical severity, G1 included 118 patients (58.7%), G2 included 50 patients (24.5%) and G3 included 33 patients (16,4%). The distribution of severe forms was not significantly different between serotypes and between primary and secondary infections. When sampled between day-1 and -3 of illness, primary infections demonstrated higher viremias than secondary infections (respectively, median 9.09 log, [IQR 8.01-10.62] and 8.41.log [IQR 7.15-9.47], p <0.01). In all, DENV-1 infections demonstrated higher viremias than DENV-4 infections (respectively, median 8.56 log [IQR 7.17-9.82] and 7.69 log [IQR 6.17-8.64], p <0.001). Median viremias were 8.60 log (IQR 7.32-9.76) in G1, 7.65 log (IQR 6.78-8.71) in G2 and 7.47 log (IQR 5.36-8.79) in G3 (p=0.003). However, the patients with severe and intermediate severity formswere admitted and sampled later than patients with uncomplicated forms (respectively, median day 5 [IQR 4-5], day 5 [4-6], day 3 [2-4], p <0.001). Conclusion: During the 2010 epidemic inMartinique, DENV1 and primary infections demonstrated higher viremias. Clinical severity was independent from serotypes and immune status.