The Public Health Service is advising people living in and travelling to the the East Coast to protect themselves against mosquitoes. 

Three cases are still under investigation, however all cases live on, or have travelled to, the state's east. 

The infection is caused by a virus and is spread by mosquitoes, Public Health's clinical director doctor Faline Howes said. 

"This is unusual. These may be the first diagnosed cases of this virus caught in Tasmania. Over the last five years, two cases of Barmah Forest virus disease have been notified - both were probably caught interstate," she said.

Many people will not get symptoms, but those who do might experience joint pain and swelling, tiredness, rashes, headaches, muscle pain, fever and chills. 

Symptoms usually start seven to 10 days after being bitten by an infected mosquito. 

Most people recover completely in a few weeks. It is diagnosed with a blood test. There is no specific treatment available so prevention is important.

If you think you may have symptoms of Barmah Forest virus see your GP. For further information call the Public Health Hotline on 1800 671 738.

Tips to protect against mosquitoes: 

• Avoid mosquito-infested areas, where possible.

• Cover-up with a loose-fitting long sleeved shirt and long pants when outside.

• Put mosquito repellent on exposed skin.

• Take special care during peak mosquito biting hours, especially around dawn and dusk, and when outdoors or camping.

• Remove potential mosquito breeding sites from around the home and screen windows and doors.