Outbreak Investigation of Chikungunya in Kovuru town, West Godavari district, Andhra Pradesh, India, 2021

  • Vector-borne
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In October 2021, an event-based surveillance system reported rise in cases of fever with arthralgia in Kovuru, a town in South India. We investigated to describe the epidemiology of the outbreak and identify potential risk factors to stop further spread.
We defined suspect case as fever >38.5°C with joint pain among residents of Kovuru, from 08 Oct to 26 Nov 2021. Outbreak was confirmed by analyzing past records of sub district hospital and district surveillance data (2017-21). We identified cases by reviewing hospital-records and community cases by house-house survey. We used ELISA-serology for laboratory confirmation and conducted entomological surveys.
We identified 75 suspect cases, of which 52(35.1%) were hospitalised between 24 to 30 October. Overall attack rate (AR) was 7%(75/1074) and household AR was 10.3% (31/302). Median age of cases was 29.3 years (IQR16-40). AR among females and males was 8.8% and 5.6% respectively (OR 1.6,1.01-2.6; p=0.04,). Of 37 cases that were tested for Chikungunya, Dengue and Malaria, 17(45.7%) were positive for Chikungunya and one for Dengue. Aedes mosquito breeding sites were found in 14(45%) houses with cases (P=<0.01, OR 50.2, 6.1-405) and 85%(52/61) of respondents did not use any personal protective measures. Entomological surveys revealed high larval indices (House Index:18.1, Breteau Index:28) which later reduced to 8.3 and 18.1 respectively, 10 days after vector control measures were instituted.
Chikungunya outbreak was confirmed after investigating cases of fever with joint pain that were reported from Kovuru and with supporting evidence of no such clustering during past three years. Favourable peri-domestic mosquito breeding coupled with inadequate personal protective measures possibly led to Chikungunya outbreak, which resulted in debilitating rheumatic manifestations among the Kovuru residents. We recommended a coordinated and multidisciplinary approach addressing behavioural health promotion and conduct of integrated vector surveillance and control measures to prevent future outbreaks.

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