Abstract
BackgroundThis study was conducted to identify epidemiological characteristics of the first documented CHIK fever outbreak in China and evaluate the effect of the preventive measures taken.Methodology/Principal FindingsFrom September 1 to October 29, 2010, China's first documented outbreak of CHIK fever occurred in the Xincun community of Wanjiang District of Dongguan city, Guangdong province; 253 case-patients were recorded, of which 129 were laboratory confirmed, with an attack rate of 1%. Before September 18th the number of CHIK fever cases remained relatively low in the Xincun community; from September 19th onwards, the number of cases increased drastically, with an outbreak peak on October 4th. Cases were distributed across nine small village groups in the Xincun community, with an attack rate of 0–12% at the village level. The household attack rates ranged between 20% and 100%. No significant difference was found in the attack rate between males and females. There was a significant difference in the attack rate in different age groups (chi-square = 18.35, p = 0.005); highest in patients aged 60 years or older and the lowest in patients aged under 10. The major clinical characteristics of patients are fever (100%), joint pain (79%) and rash (54%). Phylogenetic analysis of the E1 gene on the five earliest confirmed cases showed that the strains of CHIKV isolated from their sera were highly homologous (up to 99%) with isogeneic strains isolated in Thailand in 2009. After control measures were taken, including killing adult mosquitoes and cleaning breeding habitats of Aedes mosquitoes, the Breteau index and Mosq-ovitrap index decreased rapidly, and the outbreak ended on October 29.Conclusion/SignificanceThe infection source of the outbreak was imported. Cases showed obvious temporal, spatial, and population aggregation during the outbreak. Comprehensive control measures based on reducing the density of Aedes mosquitoes were effective in controlling the epidemic.
Highlights
CHIK fever is a viral disease mainly characterized by fever, rash, and severe joint pain
First isolated in Tanzania in 1952 [1], CHIKV is most commonly transmitted to humans through the bite of an infected Aedes mosquito
A suspected case was defined as a possible instance of CHIK fever in any person who met all of the following conditions: 1) living in Xincun community, Wanjiang District, Dongguan; 2) experienced sudden fever with at least one symptom of the disease, such as joint pain, rash or petechiae, and musculoskeletal pain since September 1, 2010; 3) did not undergo any confirmation test, or results of confirmation tests for both CHIKV nucleic acid and CHIKV IgM were found to be negative
Summary
CHIK fever is a viral disease mainly characterized by fever, rash, and severe joint pain. CHIK fever has become extensively prevalent in tropical and subtropical regions such as Asia, Africa, and Indian Ocean islands, and is an increasingly serious public health problem [2]. The land area of Dongguan is 2,465 square kilometers, and the permanent population is 8,220,237. It consists of four districts and 28 towns. The major mosquito-borne diseases in Dongguan City have been dengue fever and malaria. Cases of malaria are all sporadic, with Anopheles sinensis and Anopheles anthropophagus being the major transmission vectors. Dengue fever cases are most commonly sporadic imported cases, with Aedes albopictus being the only transmission vector. This study was conducted to identify epidemiological characteristics of the first documented CHIK fever outbreak in China and evaluate the effect of the preventive measures taken
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