Dengue outbreak in Taiwan is the deadliest ever mosquito-borne disease with a death toll of 42, double the number that died in 2014, said authorities on September 24.
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 Center 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 mosquitoes, 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," said, Chuang Jen-hsiang, CDC's deputy director.
"It's likely at its peak right now. The epidemic across Southeast Asian countries is generally more serious this year," he added.
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 Organization.
The virus, for which there is no vaccine, can lead to vomiting, bleeding, and breathing difficulty in more severe cases.
Cases in Thailand have nearly tripled this year while Malaysia also saw a surge in infections, with 219 deaths as of September 20, according to the CDC.
Local media have reported the epidemic hitting tourism in Tainan, a city with a population of 1.88 million, which draws visitors with its historic architecture and reputation as Taiwan's best food destination.
Businesses have seen a 50 percent drop in visitors since the outbreak, United Daily News reported earlier this month.