The NT’s director of Medical Entomology says while this is not the worst mozzie season on record, “it is very bad at the moment” and could possibly get worse in the coming days due to another big tide this week with cases of Ross River virus expected to rise.

NT Director of Medical Entomology Nina Kurucz said that the salt marsh mosquitoes can fly up to 50 kilometers and are coming up from the extensive swampland.

“Unfortunately, there’s not much you can do about that. And this is why we are asking people really to be vigilant,” she told ABC Radio Darwin on Monday.

She said while Ross River Virus cases have been low so far this season, an increase in cases could be expected over the next few months due to high humidity levels and increase in the lifespan of mosquitoes.

“While salt marsh mosquitoes usually trigger the start of the Ross River virus season, the common banded mosquitoes are the principal vector, with this species increasing in numbers following the first monsoonal rains,” she said. “Some receptacle breeding mosquitoes in urban areas can also transmit the Ross River virus.”

Ms Kurucz said that the health department is expected to rollout a big insecticide aerial spray on Friday in swamp areas close to the northern Darwin suburbs and going to spray out by hand throughout the Darwin areas to kill mosquitoes at their larval stage.

“We are mainly using an insecticide called BTI that’s actually live bacteria,” she said.

“It is very target-specific and not harmful to humans at all. So, we just dip it in the water where we know the mosquitoes are, and they ingest that bacteria, and it kills the stomach lining.

“So, once you put that out it’s only active for a few hours, and you see the effect pretty much straight away within a few hours.”

When asked if the health department would also do fogging in some areas, she said it is not very effective and would kill any insect it encounters.

“Unfortunately, it is not targeting specific [insects] it would kill any insect it encounters,” she said. “And we are not doing any fogging unless there’s an actual disease outbreak and the reason is that the fog is very short lived.”

The NT Health department defines the Ross River virus as a debilitating disease, with symptoms including swollen and painful joints and muscles, a red rash, fever, fatigue and swollen glands.

“As there is no vaccine, personal protection from mosquito bites is the best defence,” the department said in a statement.

Suggested measures to avoid mozzie bites include avoiding locations where mosquito activity is high, especially after sundown and using a protective repellent containing 20 per cent DEET or picaridin or extract of lemon eucalyptus (PMD) at a concentration of at least 30 per cent as a supplement to protective clothing, with creams providing best protection, among others.