Epidemiological investigation of chikungunya outbreak, West Kalimantan, Indonesia

Abstract

BackgroundChikungunya is a vector-borne infection with high morbidity rate and associated with debilitating prolonged polyarthritis and substantial socioeconomic impact. On 4 January 2010, a chikungunya outbreak was reported in Sukadana Subdistrict, West Kalimantan, Indonesia. ObjectiveAn epidemiological investigation was conducted to identify the risk factors for the outbreak and recommend control measures. MethodA case-control study was conducted to identify the risk factors of the outbreak. The cases were residents who had major clinical symptoms of chikungunya that were identified by active case finding through the affected area while controls were neighbor of the cases. Interviews were conducted to collect demographic and clinical data as well as the risk factors of infection. The venous blood from ten patients, selected randomly, were collected and tested for diagnosis confirmation. ResultsDuring 12 December 2009 and 10 January 2010, a total of 65 chikungunya cases were identified with no death. Seven out of ten blood samples were confirmed as chikungunya cases. All of the patients had fever, rash and arthralgia while headache was reported in 43% of the cases. The attack rate was 17.3% (range 3.9–22.6%) and those aged >44 year old had the highest attack rate. In multivariate model, those farming in the forest and those who had poor practices in eliminating mosquito breeding sites had higher odds of having chikungunya, with adjusted OR: 10.66 (95%CI: 3.95–28.79) and adjusted OR: 3.51 (95%CI: 1.35–9.13), respectively. ConclusionsFarming in the forest and poor vectors control are two risk factor of chikungunya infection. Therefore, using anti-mosquito repellent when farming and continuous and coordinated mosquito breeding sites elimination are recommended.