Application Of A Framework For Horizon Scanning And Risk Assessment On The Risk Of Importation Of West Nile Virus To Singapore

Background: Reports of an outbreak of West Nile Virus (WNV) infection in the Central Macedonia region of Greece in August 2010 followed by unusually large numbers of WNV cases in the European region were picked up through our routine horizon scanning for news on potential public health threats of international concern. Singapore is along the East Asian-Australasian flyway for migratory birds, and Culex mosquito is present in Singapore. We conducted an assessment of the risk of importation of WNV infection to Singapore to: (i) determine the likelihood of a WNV outbreak in Singapore, (ii) understand the possible consequences and potential downstream impact, and (iii) facilitate implementation of prevention and control measures should an outbreak occur in Singapore. Methods: We applied the framework for horizon scanning and risk assessment developed by the Ministry of Health, Singapore. This framework enables the public health system of Singapore to detect early warnings of events that may constitute public health emergency of international concern (PHEIC), analyze the risk that these events pose to Singapore, and respond to them in a timely manner. The risk assessment was based on possible routes of introduction of WNV into Singapore, and surveillance programmes in Singapore, taking into account epidemiological characteristics of WNV, clinical manifestations, diagnosis and treatment of WNV, and risk factors. Inputs from various local agencies were incorporated. Results: The WNV may be introduced into Singapore through (i) infected migratory birds, (ii) importation of infected birds or other animals, and (iii) international travel of infected persons to Singapore. To date, the virus has not been detected in the surveillance of WNV in humans, migratory and resident birds, as well as mosquitoes. Thus, the likelihood of a WNV outbreak in Singapore is considered ‘unlikely’. Conclusion: Our qualitative analysis provided a systematic approach towards the assessment of the risk posed by WNV to Singapore. The WNV situation in North America, Europe and countries with significant travel links to Singapore, should be closely monitored for factors that might change the current risk assessment, and to allow the implementation of timely and appropriate control measures. Vector control remains the cornerstone for controlling mosquito-borne diseases.