Dengue cases in Australia have reached a 20-year-high in 2016, according to the Health Department. Last year, over 2,000 cases were confirmed in the country, which is said to have been driven by infected travelers from tropical places returning to Australia.

“Dengue has been a problem globally for 20 years, and in the last 10 years we have seen epidemic spread of the virus through many countries in our neighborhood,” said the University of Sydney mosquito expert Cameron Webb. “The chance of travelers being infected may well be increasing.”

The expert also said that the increase in the reported cases could be also be the result of doctors conducting more assessments with travelers. A patient may need a few weeks to fully recover from dengue. Victoria and New South Wales had 461 and 450 cases, respectively, last year. In Western Australia, 553 cases were reported, making it among the highest of all Australian states and territories.

In Western Australia, 553 cases were reported, making it among the highest of all Australian states and territories. People in the ages of 25 to 34 represent majority of dengue cases in 2016. One in four of the 2,129 people this age group were affected last year.

The state with the highest cases of dengue is Queensland. Experts explain that Queensland is one of the places where mosquitoes can spread the virus, causing local outbreaks. Still, researchers say that the cases in Queensland are lower than the previous years because of the Eliminate Dengue program. The program involves immunizing the local mosquitoes in tropical areas against the dengue virus.

Experts say that dengue infection can be prevented by simply applying mosquito repellents. Those Australians who go to tropical places like Bali can utilize this method to prevent getting dengue. Experts also say that tourists from Australia usually assume that the mosquitoes in Bali were only active in the afternoon but these insects actually bite all day. So, precaution is urged to keep these tourists protected.