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WITH more than 150 people struck down, the dengue fever outbreak in Cairns has been declared an epidemic.

In the worst outbreak of dengue fever since before World War II, 161 people in Cairns and nine in Townsville have been confirmed to have contracted the mosquito-borne disease.

Queensland Health's Dr Linda Selvey said the Cairns outbreak was of a type of dengue fever more virulent than that found in Townsville.

Dr Selvey said more people were having to be hospitalised, with one person requiring several days in intensive care.

"We are really concerned how quickly the number of cases have grown, how quickly it has moved to a range of different suburbs, the short incubation time which makes it difficult to control and the fact it's making people sicker," Dr Selvey told AAP.

"People are getting sicker than we normally see and children are getting sick where as previously children weren't necessarily getting sick."

There are four types of dengue fever and each type has different strains.

Cairns is dealing with an outbreak of a strain of dengue type three, believed to have originated from Indonesia.

Dr Selvey said Townsville had a different strain that was not as virulent.

Residents are being urged to empty water from any containers that could act as a site for the mosquito to lay its eggs.

Dengue fever symptoms include fever, sunburn-like rash, sore eyes and lethargy.