Northern Territory health officials have warned people to protect themselves from insect bites after two rare mosquito-borne viruses were detected.

Northern Territorians have been urged to protect themselves from mosquito bites after two rare and dangerous viruses borne by the insects were detected.

Murray Valley encephalitis (MVE) virus and Kunjin virus were found in the Top End and Barkly regions during routine screening, NT Health says.

"The results of recent testing indicate widespread MVE and Kunjin virus activity throughout the Territory, medical entomologist Bill Pettit said on Thursday.

"Although mosquito numbers are currently relatively low in Top End urban areas and Central Australia, they can still occur in relatively high numbers in rural areas, especially those close to swamps and wetlands."

The announcement follows the recent death of a resident on the Tiwi Islands, north of Darwin, following a case of a mosquito-borne encephalitis, which is inflammation of the brain tissue.

Health authorities said they are still investigating which virus the resident was infected with in March but the MVE or Kunjin virus are the most likely.

Both viruses are transmitted by a bite from an infected mosquitoe, which mainly breed in vegetated freshwater habitats.

MVE is a rare disease that can be fatal.

Symptoms include severe headache, high fever, drowsiness, tremor, seizures and in some cases the disease can progress to delirium, coma, permanent brain damage or death.

Kunjin virus is also rare but endemic in tropical parts of Australia, like the north of the NT, but rarely leads to encephalitis.

People in the NT have been urged to cover up after sundown, use repellent and avoid outdoor exposure around mosquito-prone areas.

Residents are also advised to avoid outdoor exposure within two kilometres of swamps, creeks, rivers, billabongs and other flooded or low-lying areas, NT health said.

It comes five weeks after dengue mosquitoes were found in Tennant Creek, about 1000km south of Darwin.

They were thought to have hitched a ride from tropical north Queensland, where Dengue fever often occurs during the wet season.

No cases of dengue fever were diagnosed in the Territory following the discovery of the mosquito.