Taiwan is suffering its deadliest ever outbreak of mosquito-borne dengue fever with a record high of 42 deaths.

Taiwan is suffering its deadliest ever outbreak of mosquito-borne dengue fever with a record high of 42 deaths, double the number that died in 2014.

Last year saw 15,732 cases - by far the highest in nearly three decades - with this year shaping up to overtake.

The total number of cases for 2015 has already hit 15,282, the Centre for Disease Control (CDC) said, the majority of them in southern Tainan City.

Unusually hot weather has caused the increase, the CDC said.

High temperatures and humidity encourage breeding of mosquitos, which is why countries with tropical climates - including Taiwan - tend to be plagued by dengue fever every year.

"This year saw temperatures in Tainan and (the southern region of) Kaohsiung at their highest in 30 years," Chuang Jen-hsiang, CDC's deputy director, told AFP.

"It's likely at its peak right now. The epidemic across Southeast Asian countries is generally more serious this year."

Another 36 deaths are being examined for their connection to dengue fever.

Dengue fever - which causes high fever, headaches, itching and joint pains - affects two million people across the globe annually, with the number of cases up 30 times in the last 50 years, according to the World Health Organisation.