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Nearly 2 million dengue inspections this year: Dr Vivian Balakrishnan

Speaking in Parliament, the Minister for the Environment and Water Resources said the Sanofi vaccine has not shown adequate success rates against the types of dengue predominant in Singapore.

SINGAPORE: The National Environment Agency has conducted nearly 2 million dengue inspections this year, and deployed more than 1,000 Gravitraps in dengue clusters for mosquito-control purposes, Minister for the Environment and Water Resources Dr Vivian Balakrishnan said in Parliament on Monday (Aug 4).

There have been more than 12,000 reported dengue cases so far this year, Dr Balakrishnan said. This dengue epidemic, which has been ongoing since 2013, was driven by three factors:

  1. There was a switch in the predominant dengue serotype to DENV-1 last year. This strain of DENV-1 virus spreads more rapidly than other strains in Singapore and now accounts for about 90 per cent of the current infections.

  2. Singapore's general population lacks immunity to dengue due to cumulatively low incidence over the last two decades.

  3. The mosquito Aedes aegypti is still endemic in Singapore despite efforts over the years.

Dr Balakrishnan said the National Environment Agency (NEA) has increased the frequency of inspections and taken enforcement action against errant contractors, whose sites have seen the breeding of mosquitoes. So far this year, 62 Stop Work Orders have been issued and 14 contractors prosecuted in court, he said.

Penalties have also been levied on homeowners, town councils and other landowners when breeding is found within their premises, he added. This year, the fines levied ranged from S$200 for home owners to S$39,000 for construction contractors.

BIOLOGICAL INTERVENTION

When it comes to developing new tools to tackle dengue, Dr Balakrishnan said NEA's Environmental Health Institute (EHI) is working with local researchers to utilise the Wolbachia bacteria.

"We are currently studying the feasibility of using Wolbachia-carrying male Aedes aegypti mosquitoes to suppress the mosquito population in Singapore. A Dengue Expert Advisory Panel consisting of international and local experts has been appointed to provide scientific advice on the safety and effectiveness of this technique in our context. As this is a novel biological intervention, we will not embark on any field trials unless it is clear that safety is totally assured."

Responding to questions from Members of Parliament on whether the Government will approve the Sanofi vaccine, Dr Balakrishnan said more needs to be done to ensure its efficacy. "It showed some promise, but to be honest with you, my frank opinion is that it is not good enough. Why do I say that? It showed reasonable effectiveness, about 75 per cent for Type 3 and Type 4 serotypes of dengue," he said.

"Against Type 1, which is the current problem we are having, it is only about 50 per cent effective. Against Type 2, which is the predominant dengue serotype which circulates in Singapore, it was only about 35 per cent effective. Those rates of efficacy are not, in my opinion, good enough."

Dr Balakrishnan said that Singaporeans must continue to stay vigilant and keep their homes free of breeding habitats. He said since January, more than 4,000 breeding sites have been found in residential premises.

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