Aggressive environmental control to stop the largest dengue fever outbreak in Hong Kong, 2018

  • Vector-borne
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Background:
Dengue fever (DF) was not endemic in Hong Kong, though sporadic cases of locally acquired DF were reported. In August 2018, the Centre for Health Protection (CHP) of Hong Kong recorded a DF outbreak in a local park named Lion Rock Park (LRP).

Methods:
We reviewed notifications of DF cases received by CHP from May to October 2018. We defined locally-acquired case of DF as those who have dengue fever compatible symptoms with laboratory confirmation, and have not travelled to endemic area within 14 days of symptom onset. All locally-acquired cases with exposure to LRP or its surrounding area were included in the outbreak. We conducted epidemiological and laboratory investigations for all cases for epidemiological linkage, possible common exposure and common source of infection.

Results:
We identified 19 cases in the outbreak. They involved 10 males and 9 females (47.3%) with median age of 55 years (17-78). They had onset of symptoms from August 2 to 20. Majority presented with fever (94.7%) and myalgia (89.5%). None had severe dengue complications. Eleven cases had DENV-1 virus with identical nucleotide sequence. The outbreak was established on August 15 when epidemiological investigation of 3 locally acquired DF cases revealed geographical linkage to LRP. Risk assessment suggested the park was the major source of infection and we promptly recommended closure of the park on August 17 for intensive anti-mosquito operation to stop the spread of the disease. The outbreak was effectively controlled after closure of the park with the last case had onset of symptoms on August 20. The outbreak was declared over on October 10.

Conclusion:
Prompt anti-mosquito control can stop an evolving dengue fever outbreak. Prompt epidemiological investigation for early targeted control can help to prevent the disease becoming endemic in Hong Kong.

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