11 people in southern Thailand have been infected with a strain of malaria that primarily infects macaque monkeys.
Health authorities said the southern provinces of Trat, Songkhla and Ranong were the areas most at risk for Plasmodium Knowlesi infections.
Koh Chang Island reported nine such infections, with the rest reported in Bo Rai.
According to the governor, Chamnanwit Terat, most of the patients lived and/or worked near forests inhabited by the macaque monkey.
Although they have since recovered, Mr Chamnanwit said they were told to remain vigilant to prevent the disease from spreading further within the community from the macaque monkey.
In the past year, 70 people have contracted malaria, which is caused by a parasite.
P. knowlesi, like the other parasites responsible for malaria, can only be spread by its vector, the Anopheles mosquitoes.
See: Anti-mosquito guide: all about mosquitoes to protect yourself from them
In 2004, researchers in Sarawak, Malaysia found that the parasite was able to infect humans and long-tailed and pigtailed macaques.
The provincial administration plans to inform the public about the threat posed by Plasmodium Knowlesi infections, Chamnanwut said.
To avoid getting infected, residents living near forest areas are advised to apply mosquito repellents before going out and sleep with mosquito nets covering them.
According to the Department of Disease Control, residents living near wild macaque habitats are also advised to take extra precautions.
On Koh Chang, a popular tourist destination, live at least 1,000 long-tailed and pig-tailed macaques, according to park chief Dusit Samuttrakapong.
About Plasmodium knowlesi and the macaque monkey
P. knowlesi is now recognized as the fifth type of Plasmodium responsible for malaria in humans.
Infections have been reported across Southeast Asia.
According to molecular, entomological and epidemiological data, human infections with P. knowlesi are not of recent onset, and P. knowlesi malaria is primarily a zoonosis.
In humans, infections were not diagnosed until molecular detection methods distinguished P. knowlesi from the morphologically similar P. malariae.
Infections caused by P. knowlesi in humans are life-threatening, but if detected early enough, they can be treated.
Source: Chiang Rai Times, PubMed