High tides are elevating numbers, and the Top End Health Service is urging people to protect themselves.

Salt marsh mosquitoes can carry the Ross River virus.

And although the high risk period for RRV starts in December, the virus can be contracted all year around.

"This means people need to start taking precautions to avoid being bitten," Director of Medical Entomology Nina Kurucz said.

While all efforts have been made by Darwin's Medical Entomology team to control known breeding areas, they will likely be out in swarms over the next week at least.

Ms Kurucz said the team sprayed 170 hectares of salt marsh mosquito breeding area in swamps near Darwin's northern suburbs.

"This is the time of the year when high tides and rainfall trigger extensive salt marsh mosquito breeding until monsoonal rains flood all the breeding areas," Ms Kurucz said.

She said there is only a narrow window of about three days to effectively spray the larvae.

Darwin is surrounded by swamps and with a flight range of 50km, there is no stopping mosquitoes from making their way into Darwin, Palmerston and rural areas.

There are just over 100 species of mosquito in the NT, but according to the government, the northern salt marsh mosquito, Aedes vigilax, "is the most important pest mosquito in the Top End because of its aggressive biting habits during the day and night".

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