The CDC is concerned that, according to World Health Organization standards, it is the first case of the disease contracted locally.

"We know this is an introduced [domestically transmitted] case because the patient never traveled abroad," said Shih Wen-yi, deputy director-general of the CDC. "We are still in the process of investigating and more information will be forthcoming. But we believe that this man was infected by people who had traveled abroad recently," said Shih Wen-yi, deputy director-general of the CDC.

According to Shih, since the WHO declared Taiwan malaria-free in 1965, Taiwan has continued to see isolated cases of malaria each year.

Nineteen cases have been reported so far this year. Eighteen of these were a result of people being infected abroad, while the most recent case was contracted in Taiwan.

"One case of malaria is not a big deal, but if it begins to spread to more people, then we have a problem," Shih said.

The CDC stated that of the roughly 17 types of mosquitoes in Taiwan, only the Anopheles minimus spreads the disease.

These mosquitoes inhabit Pingtung, Tainan, Taitung, Hualien and Kaohsiung counties.

The mosquito can be identified by its five black and white stripes and a body angled upward.

The infected patient, a 57-year-old Aboriginal man from Taitung County, has been receiving treatment in the Mackay Memorial Hospital since he began showing symptoms on Tuesday.

Shih warned the public to stay away from mountainous areas and to avoid going out at night. He also said that those planning to travel to areas where malaria is common should visit the CDC before leaving.

According to Shih, some 3 million people die of malaria each year worldwide. He said, however, that given modern medical knowledge, identified cases of malaria are easily treatable.

Symptoms of the disease include fever, headache, excessive sweating, nausea and diarrhea. Because the incubation period ranges from 11 to 28 days, CDC officials are investigating the places the infected man visited over the past month.