The Northern Territory Health Department says recent monsoonal rains in the Top End have led to a mosquito population boom.
It says the weekend rains encouraged backyard mosquitoes to begin breeding.
The Director of Medical Entomology Peter Whelan says the risk of being bitten by a disease-carrying mosquito has doubled.
"We've got more mosquitoes around now capable of carrying Ross River Virus and Barmah Forest virus," he said.
He says Territorians need to be careful of the heightened risk.
"Have a look around your own backyard and get rid of the backyard mossies.
"If you're going out into the environment or you live near creeks or swamps make sure you avoid the worst problem areas in the worst time of the day which is generally in the mornings and evenings."
© ABC 2013
18:04 EDT The weather bureau has urged residents in Queensland's Gulf to remain on cyclone alert as ex-Tropical Cyclone Gillian moves overland.