Mosquito fogging may look like the authorities are cracking down on the airborne pests but it is not actually very effective, dengue expert Duane Gubler said yesterday.

Professor Gubler added that countries need to move away from such "easy approaches" and examine newer methods with more potential, such as introducing sterilised mosquitoes and using new pesticide compounds.

"It doesn't mean we won't spray," said Prof Gubler, who chairs Singapore's Dengue Expert Advisory Panel and is founding director of the Emerging Infectious Diseases Programme at Duke-NUS Medical School. "There will continue to be a place for spraying... What we have to do is get away from the easy approach of spraying and find out what really works."

He was speaking at a conference organised to commemorate Asean Dengue Day on June 15. The conference, which ends tomorrow, drew 150 participants from 24 countries.

They are discussing pest control methods and how well pilot projects to reduce the mosquito population have fared.

The National Environment Agency has pointed out previously that the "severe limitation" of mosquito fogging is that it also kills insects that prey on mosquitoes.

It also noted that outdoor fogging and indoor spraying and misting are effective only if the chemicals come into direct contact with the mosquitoes.

1,113 cases so far this year

Singapore's two largest dengue clusters are in the eastern part of the island, with one in the Bedok North area responsible for 64 cases. A smaller one of 11 cases is in Tampines, with 10 other clusters scattered across the island, each with fewer than 10 dengue victims. A cluster refers to at least two cases reported within 150m of each other over a two-week period. There have been 1,113 dengue cases reported so far this year, with 54 surfacing last week. This is relatively low: During the worst dengue epidemic - in 2013 - more than 22,000 people came down with the disease. But Singapore cannot afford to be complacent about its low dengue rates, Minister for the Environment and Water Resources Masagos Zulkifli said yesterday. "We must keep the public continually alert to eliminate mosquito breeding grounds all year round, for the sake of their loved ones," he added. "Public campaigns on dengue prevention and vector control will be a part of our lives as long as there is no effective vaccination against dengue." Linette Lai

"Thus, (they) have to be repeated frequently as new batches of mosquitoes will continue to emerge until all breeding habitats are found and removed," it said.

Dengue numbers have remained relatively low since the start of last year, with fewer than 100 new cases a week.

There were 2,772 dengue cases reported for the whole of last year. In comparison, during Singapore's worst dengue epidemic in 2013, more than 22,000 people were infected.

Prof Gubler said that although the low dengue numbers are good news and highlight the effectiveness of national mosquito control programmes, they could also be attributed to the natural epidemic cycle.

There are four strains of dengue, and cases tend to spike when a new strain becomes dominant.

Minister for the Environment and Water Resources Masagos Zulkifli told the conference: "This is a never-ending war... To keep winning this war, we must innovate, invest in new technology, and collaborate and share knowledge.

He also stressed that the general public must be "continually alert".