The Department of Disease Control (DDC) said a brain disease caused by Naegleria fowleri, commonly referred to as "brain-eating amoeba", is not contagious between people.
The announcement came after The Korea Herald reported on Monday that a Korean national in his 50s died last Wednesday of the brain disease after returning from a four-month stay in Thailand.
According to DDC's director-general, Tares Krassanairawiwong, most patients diagnosed with the disease caused by Naegleria fowleri had a history of exposure to unclean water from natural sources.
Naegleria fowleri is an amoeba that lives in soil and warm freshwater, enters the body by inhalation through the nose, and travels to the brain.
Patients can be diagnosed with the disease one to 12 days after contracting the amoeba.
They may experience severe headaches, fever, vomiting and a stiff neck. The disease can progress and result in death.
Dr Tares said however: "The amoeba is not transmitted from human to human and it cannot be transmitted through clean drinking water."
The disease is rare in Thailand. According to the DDC, only 17 patients were diagnosed with it in Thailand from 1983 to 2021.
Some 82% of them, most of them male patients aged eight months to 71 years, died after the diagnosis.
Dr Tares suggested people avoid swimming in unclean water sources or using it to clean their noses, as way to help prevent the amoeba from entering the body. He also suggested they use sterilised or saline water for nasal cleaning if they accidentally inhale unclean water. Dr Tares added that anyone who displays symptoms should seek immediate medical treatment.
A total of 381 cases of Naegleria fowleri have been reported around the globe since 2018, including in India, Thailand, the United States, China, and Japan, the Herald reported.