Although Singapore has one of the world's best mosquito control and dengue surveillance programmes in the world, more needs to be done, including using new technological tools to plug the gap between detection and control. This is according to experts who are in Singapore for the fourth Asia-Pacific Dengue Workshop, jointly organised by the World Health Organization (WHO). WHO estimates that dengue affects between 50 million and 100 million people each year, and is now endemic in more than 100 countries, compared to nine in 1970.
DENGUE SITUATION IN SINGAPORE
In Singapore, what is interesting is that the country experienced its first major dengue outbreak in the 1960s. After this was addressed successfully, the nation experienced a period of low incidence for about 15 years. Ironically, this could be one of the reasons for the current epidemic, a reduced immunity to current serotypes. In 2013, there were 22,000 reported dengue cases, and this year, it has reached more than 13,500.
Dr Raman Velayudhan, coordinator of the Vector Ecology & Management Unit at the World Health Organization, said: "Singapore also has the largest number of people travelling in and out. People may come in infected and provide your mosquitoes with infection and then they fly out in 48 hours. You really do not know what is happening with so much movement of people. This is definitely a big problem. So more integrated surveillance would be needed."
Dr Raman said this includes an early detection of a change in dengue serotypes. He added that new technologies to control mosquito populations could benefit Singapore, and WHO is evaluating about 18 different ones that could see large-scale applications in about three years.
These include biological control agents, like the wolbachia bacteria, as well as traps. However, Dr Raman noted that Singapore still needs to intensify its hunt for mosquito breeding sites that could be evading authorities.
Vaccines could also increase herd immunity. Pharmaceutical company Sanofi concluded phase three of the Asian trial of its new dengue vaccine recently, and experts said its American trial could be released over the next two months.
However, local authorities point out it is not effective enough for the two most common types of dengue virus in Singapore. The vaccine has an efficacy level of 50 per cent for Dengue Type 1 virus, and 35 per cent for the Type 2 virus.
Still, there are some advocates of the vaccine among experts. Professor Duane Gubler, founding director of the Program in Emerging Infectious Diseases at Duke-NUS Graduate Medical School, said: "It is not a totally effective vaccine. It has only 56 per cent efficacy. A lot of people do not agree with it, but you do not need a balance tetravalent vaccine to control dengue. What you need is a vaccine that will protect against two or three serotypes."
"You come in to an endemic area like Singapore where you already have many people who have the antibody and have had an infection, one or more. You give them a vaccine that protects against two or three viruses," added Prof Gubler.
Prof Gubler said what the vaccine will do is broaden the immune response to the point of reducing transmission. He added that other vaccines like Merck and Takeda are also promising and cost-effective, but they have not reached phase three trials.