Questions/Answers

The integrated vector control programme led by the National Environment Agency (NEA) aims to reduce the health and economic burden of arboviral disease transmission in Singapore. The programme has contributed to a decline in dengue infections and dengue-related deaths in Singapore and has been cited by the World Health Organization (WHO) for its success* . Though it targets dengue, its benefits extend to the control of other mosquito-borne diseases such as Zika, Chikungunya, Yellow Fever, West Nile Virus and Japanese Encephalitis. The programme utilizes a sustained coordinated effort to keep the mosquito population low even in inter-epidemic periods and adopts a risk-based approach, leveraging on sophisticated analysis of near real-time field data and predictive algorithms, to optimize the use of scarce resources for targeted pre-emptive responses. Its success is attributable to the integrated vector control approach across the government, community and private sectors, comprising key elements of the Integrated Vector Management (IVM) strategy endorsed by the WHO** . Lastly, the programme strengthens domestic resource mobilization and international support in capacity building efforts especially in developing countries. *Global vector control response 2017-2030. Geneva World Health Organization; 2017. **WHO. Global strategic framework for integrated vector management. Geneva, World Health Organization, 2004 (WHP/CDS/CPE/PVC/2004.10).

An integrated vector control approach harnesses the collective knowledge, resources, equipment, and commitment of stakeholders, communities and individuals to sustain efforts. The integrated approach covers preventive action taken at high risk areas, and recovery plans that are delivered promptly to the most vulnerable and susceptible groups, through systematic processes that are continuously refined through iterative reviews. A broad range of operational, scientific, legislative, behavioural and advocacy-related tools and methodologies are employed. This multi-pronged effort mobilizes multiple government agencies and institutions, the research community, training centres, field inspectors, healthcare networks, industry associations, and community organizations to achieve a better outcome collectively.

Annually, about 390 million people are estimated to be infected with dengue. In 2017, the WHO set goals for a 75% reduction in vector-borne disease mortality and a 60% reduction in vector-borne disease morbidity. WHO has acknowledged that vector control has linkages to SDGs 1, 3, 6, 11, 13 and 17* . Singapore’s integrated programme contributes to these SDGs in combating tropical and communicable diseases, addressing the associated gender and social-economic divide and strengthening capabilities through global partnership for sustainable development. *World Health Organization. Regional Office for South-East Asia (2017). Vector control. World Health Organization. Regional Office for South-East-Asia. http://www.who.int/iris/handle/10665/258546

With the low total fertility rate in Singapore, every child is especially precious. Mosquito-borne diseases pose a particular threat to this vulnerable group. Our integrated programme has made a positive impact on children over the years. From 1977 to 2000, the proportion of reported dengue infections below 15 years of age in Singapore decreased from 0.3 to 0.07* . Before 2005, our programme was implemented largely by its health and environment agencies with limited support from other government agencies. This posed limits on the effectiveness of the programme. With the formation of the Inter-Agency Dengue Task Force in 2005, there was a marked improvement in information sharing across government agencies and other stakeholders, through a formal platform for cross agency conflict resolution, greater coordination of shared resources and more extensive vector control coverage of areas requiring intervention. There was also a fundamental change from a reactive control approach to a pre-emptive one where there is sustained effort regardless of the transmission intensity. *Effect of increasing age on the trend of dengue and dengue hemorrhagic fever in Singapore, Ooi EE, Goh KT & Wang NCD, Int J Infect Dis 2003; 7: pages 231-232

The integrated approach provides a scalable framework for activating quick and coordinated responses to the dynamic disease situation, even for new diseases such as Zika. It facilitates rapid testing and deployment of new tools, for example, dengue predictive models and NEA-designed Gravitraps to enhance surveillance, drones for inspections and dispensing of larvicide, and use of Wolbachia-Aedes technology to suppress the mosquito population. Designing out water stagnation in building structures, such as improved roof drainage systems and mosquito-proofed floor gully traps, and policy innovations, such as mandating Environmental Control Officers for large construction sites, add to our evolving arsenal of measures.

To the best of our knowledge, NEA is the first to implement the use of dengue predictive models in informing the timing and focus of its mosquito control operations. Gravitraps represent an important evolution in the use of portable surveillance tools. Where its predecessor the Ovitrap was only capable of trapping mosquito eggs, the Gravitrap additionally traps the female Aedes mosquito, this preventing further dengue infections. Drones have been used in other contexts. Though the Wolbachia-Aedes technology was conceived elsewhere, Singapore is among the first to evaluate this novel control method for a cityscape environment.

One key initiative is UNITEDengue, a cross-border network founded by ASEAN countries for sharing dengue data and knowledge. International and regional events, training attachments and study visits are hosted by the NEA. Another unique capacity building activity is the Singapore International Dengue Workshop – a joint initiative by NEA and the World Health Organization – providing a holistic view of dengue management, with an emphasis on inter-sectoral collaboration. Over five workshops, more than 326 public health practitioners from 45 WHO Member States have been trained. Practitioners gained knowledge, skills and confidence, and successfully applied these back in their own countries.

Singapore’s inter-disciplinary vector control programme is presently supported by approximately 760 officers involved in the management and execution of control operations, engagement of stakeholders, and epidemiological investigation and regulatory work. Approximately 90 officers are involved in scientific research to inform strategies to augment policy and practice. Between 2000-2009, the economic impact of dengue in Singapore, without control and intangible costs, was estimated between US$0.35 billion and US$0.65 billion (based on 2010 dollar values). Comparatively, control expenditure amounted to US$0.5 billion in the same decade. Today, the programme costs about US$52 million per year, largely due to high manpower costs.

The economic resources invested, which represent a fraction of the benefits, corroborates with NEA’s commitment to safeguard public health, amidst rising risks from urbanization and emergence of new diseases. The resultant high public and international confidence in Singapore as a good place to live, work and play underpin the economic sustainability of our integrated approach. Nonetheless, NEA continues to refine its programme, to rely more on technology in place of manpower, to achieve greater resource sustainability. The integrated approach, with its strong focus on source reduction and environmental management, rather than chemical control, also contributes to a sustainable environment. The NEA also undertakes registration of all pesticides and repellents in Singapore prior to their sale to ensure that vector control chemicals have been duly evaluated for their safety and effectiveness in accordance to the WHO Pesticide Evaluation Scheme. Through encouraging the social norming of the right behaviours to reduce mosquito breeding as part of the integrated approach, society as a whole will not have to bear undue cost burden from downstream interventions. There is also social justice as areas identified with higher risks will receive greater intervention regardless of the socioeconomic characteristics of the neighbourhood.

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Yes. For an objective assessment of the impact of the integrated vector control approach on dengue, we worked with an independent academic research institution (the National University of Singapore) and rigorously modelled the historical transmission intensity of dengue in Singapore. The academic paper detailing the assessment is being prepared for peer review prior to publication.

We estimated the probability of a susceptible individual acquiring a new dengue infection in each year and also the number of dengue infections averted due to the mosquito control programme. We used the Force of Infection (FOI) to estimate how the probability of an individual acquiring a new dengue infection changed over time. We also estimated the number of dengue infections averted as a result of the control programme.

The evaluation shows substantive reductions in dengue. From 1982-1998, the disease burden in those aged 16-20 declined from 70% to 13%. From 1977-2000, the proportion of reported infections below 15 years of age decreased from 0.3 to 0.07* . The probability of an individual acquiring a new dengue infection declined from 6.5% to 1.2% in the 1960s-1980s, and maintained at 1%. Approximately 160,000 infections in Singapore were averted between 1990-2013. *Effect of increasing age on the trend of dengue and dengue hemorrhagic fever in Singapore, Ooi EE, Goh KT & Wang NCD, Int J Infect Dis 2003; 7: pages 231-232

The Inter-Agency Dengue Task Force (IADTF), comprises 29 stakeholders from the People, Public and Private sectors. The IADTF is chaired by NEA and emphasizes the importance of integration, collaboration, partnerships and inclusion. It provides an enabling platform which facilitates the resolution of cross agency issues, shares best practices, and enhances communication and coordination. NEA works closely with IADTF members to enhance their mosquito control plans. NEA conducts a national dengue prevention public education campaign annually, combining both mass publicity and on-ground outreach efforts to rally the community. Students learn the importance of dengue control in their curriculum. NEA partners community organizations and leaders, to develop localized engagement programmes, including the elderly. These partners mobilize more than 8,500 Dengue Prevention Volunteers to conduct advocacy activities at affected areas, and make house visits to encourage residents to take active measures to prevent mosquito breeding in their homes. There is high recall of campaign messages. NEA has partnered corporates to conduct dengue prevention talks and training to their staff, and create additional content and resources for the public. NEA also works with worker dormitory operators, gardeners, nurseries and travel agencies to develop outreach materials and promote greater awareness and action on mosquito control.

An integrated approach fosters greater stakeholder and community ownership in working towards a common goal. Community advocacy appears to be most effective when the threat of disease transmission is the highest. The NEA will leverage on behavioural science to further enhance the effectiveness of public health interventions undertaken outside epidemic periods. Singapore’s vector control programme requires substantial public expenditure and this may be less sustainable if demands for public resources become more competitive. To improve productivity, NEA is piloting the use of smart gravitraps which can remotely transmit information on mosquito activity and reduce the need for frequent physical inspections.