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 disease after returning from a four-month stay in Thailand.
According to the Korea Disease Control and Prevention Agency (KDCA), his genetic tests for three types of pathogens causing Naegleria fowleri were 99.6% similar to those found in a meningitis patient reported abroad.
This made the man the first patient to be diagnosed with the disease in Korea.
According to DDC director-general Tares Krassanairawiwong, most patients diagnosed with the disease caused by Naegleria fowleri had a history of choking on 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 then progressed to a critical stage, resulting in the patients' deaths.
"The amoeba is not transmitted from human to human, and it cannot be transmitted through drinking clean water," said Dr Tares.
The disease is rare in Thailand, as only 17 patients were diagnosed with the disease in Thailand from 1983 to 2021, according to the DDC.
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 them to clean their noses, to prevent the amoeba from entering the body. He also suggested they use sterilised water or saline water for nasal cleaning if they accidentally choke on unclean water.
Anyone who displays symptoms should seek immediate medical treatment, he added.
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 Korea Herald reported.