Singapore fights dengue with more mosquitoes

Singapore's got some special ammunition to fight a record outbreak of mosquito-borne dengue fever: more mosquitos.

But not just any old bugs, the ones in the six-barrelled mosquito launcher officials use have been infected with a special bacteria.

With each round, about 150 lab-reared male mosquitoes fly off in public housing blocks in search of a female companion.

The Wolbachia bacteria they carry stops diseases like Zika, Yellow Fever as well as dengue and the mosquitos can't transmit them.

And as principal investigator Ng Lee Ching explains, it leaves females unable to make more mosquitos.

"when a male mosquito mates with a female in the field, they are not compatible. So the eggs that are laid by the female are not viable, they don't hatch."

Singapore is a tiny island but it hosts a population of 5.7 million people.

It's recorded more than 26,000 dengue cases so far this year with four months to go -- worse than 22,000 in all of 2013.

The surge is due to a new strain of the disease, combined with unseasonably wet weather plus coronavirus lockdowns that left construction sites and other breeding grounds undisturbed.

"So if you can imagine, if we continue to release these male Wolbachia mosquitoes, into the field, compete with the wild type, mate with the female, you will get a gradual reduction of the mosquito population in the community."

Ng says some areas with high mosquito populations have seen up to 90% declines.

The strategy has also been successful in Australia's rural Northern Queensland, but some are skeptical whether it will work in densely urbanised Singapore:

Paul Tambyah is president-elect of the International Society of Infectious Diseases:

"Because you've got to flood the island with these mosquitoes, and people get annoyed when they see a mosquito. You know, you tell them this is sterile male mosquito, they're not going to be able to tell the difference, they're not going to grab the mosquito and examine and see whether it's a male or female. So they're going to swat them away, and that kind of defeats the purpose of your project. So it is a bit challenging to see how it's going to work in Singapore."