Chikungunya Fever Outbreak in a Candy-making Home Industry, Nagcarlan, Laguna, Philippines 2018

  • Vector-borne
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Background:
In August 2018, the Epidemiology Bureau of the Department of Health received a report regarding clustering of suspect chikungunya cases in Nagcarlan, Laguna. We conducted an investigation to determine the existence of an outbreak and its source and identify risk factors.

Methods:
We conducted a 1:2 case-control study. A suspect case was any previously well resident of Nagcarlan, Laguna with fever and joint pains from April 20-August 17, 2018. A confirmed case is a suspect case positive for chikungunya polymerase chain reaction (PCR). Active case finding and face-to-face interviews were done. A control is an asymptomatic resident negative for Chikungunya confirmatory test. Environmental and entomological surveys were conducted. Sera were collected.

Results:
We identified 252 cases. None died. One hundred fifty-four (61%) were females. Age ranged from 2-73 years (Median=34). Rainfall started in April 2018. Barangay Taytay, with the highest attack rate (37 cases per 1,000 population), has numerous candy/delicacy-making home-based industries. Workers wearing only short pants and shirts aggregate inside houses that were mostly dark. Breeding sites observed were mixing pails, drums, and axilled plants. Fogging only done in one village. House and Breteau indices were higher than standard values. Twenty-three (51%) of 45 samples were positive for chikungunya virus. Risk factor was being a candy/delicacy home industry worker (OR=9.50, 95%CI=2.53-35.63). Wearing long pants (OR=0.54, 95%CI=0.29-0.96) was protective.

Conclusion:
There was a chikungunya fever outbreak in Nagcarlan, Laguna. Entry of a viremic host from neighboring endemic areas may have been the source. Increased mosquito breeding sites and Aedes mosquito density, limited vector control measures, and poor practice of self-protection measures led to the outbreak. We should regularly conduct search and destroy activities in houses and workplaces. The community, especially industry workers and their employers, should know what appropriate self-protection measures to practice or institutionalize. Cases should be monitored, reported, and properly managed.

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