Chikungunya as an Emerging Cause of Acute Febrile Illness in Southern Sri Lanka

Abstract

Objective: The aim of this study was to determine the epidemiology of Chikungunya as an etiology of acute febrile illness in southern Sri Lanka.

MethodAs part of the Duke-Ruhuna post-Tsunami response, a joint research team established a prospective study of acute febrile illness. Between February and November 2007, the investigators enrolled 1079 patients > 2 years of age who presented with fever (>38°C tympanic) to the acute care clinics and emergency department of Teaching Hospital Karapitiya, Sri Lanka. We obtained paired sera from participants for Chikungunya diagnosis including IgG Indirect immunofluorescent assay (IFA), PCR, virus isolation, and sequencing.

Results: Of the 797 patients with available paired sera, 109 (13.7%) screened positive for Chikungunya IgG using IFA. Using a 4-fold rise in acute and convalescent sera, we identified 28(3.5%) acute infections. Additionally, we identified 12 past infections based on the presence of antibodies in both acute and convalescent sera. Among the 28 seroconversions, 10 were isolated by culture and 18 by PCR. Those with acute infections were older (40 years compared to 30 years, p=0.07), more likely males (82% compared to 60%, p=0.02) and were more often admitted to the hospital (93% vs 71%, p=0.001) compared to those without acute Chikungunya infection. Participants with acute Chikungunya infection were more likely to have joint pain (RR: 3.12, CI: 1.39, 7.00, p=0.004), muscle pain (RR: 4.86, CI: 1.87, 12.67, p=<0.001), rash (RR: 5.49, CI: 1.83, 16.45, p=0.001) and conjunctival injection (RR: 3.36, CI: 1.59, 7.10, p=0.001) than those without acute Chikungunya infection. Furthermore, viral Sequencing data confirmed the presence of epidemic African strain throughout the study.

Conclusion:Chikungunya virus was present in southern Sri Lanka and should be considered in the differential diagnosis of acute febrile illnesses. Our limited data suggest infection with the recently identified epidemic strain.