An outbreak of dengue fever has been declared in a Pacific country beloved by Australian travellers.

The Cook Islands Ministry of Health declared the outbreak last week, with a total of seven cases of the illness in the past 18 days now confirmed.

So far, the ministry said, the cases were confined to the main isle of Rarotonga, with none in the outlying islands of the Pa Enua.

The Australian government has urged people to protect themselves against mosquitoes and use insect repellent while in the country.

The tropics-associated illness is carried by certain species of mosquito.

Dengue fever is mostly imported into Australia by travellers – if a mosquito bites an infected person, that mosquito can become a carrier.

Outbreaks in Australia are largely confined to north Queensland.

Symptoms can include a sudden fever, a headache, chills, swollen glands, muscle and joint pain, fatigue, abdominal pain, nausea, vomiting, and a faint, red rash.

The severity can range from mild to severe.

Most people with dengue fever recover in about a week, according to Health Direct, but other cases can require hospital case.

Occasionally, dengue fever has proven fatal.

Severe dengue fever symptoms may develop several days after the initial systems, and include frequent vomiting, vomit with blood in it, and unexpected bleeding.

People who have any dengue fever symptoms and are concerned for their health should contact their doctor.

Anybody feeling extremely unwell should contact Triple Zero in Australia, or emergency health services overseas.