The recent deaths of two children from a rare but usually fatal brain infection transmitted by organisms thriving in freshwater have raised concerns about the risks of swimming in lakes and rivers during summer.

Health experts, however, emphasize that the disease is uncommon and early treatment can prevent fatalities.

On Friday, a mother in Fujian province in South China said on social media that her 5-year-old daughter had died from primary amebic meningoencephalitis after more than 50 days of treatment in an intensive care unit.

The girl had gone swimming and visited hot springs twice in June. She developed headaches, a low-grade fever and vomiting on June 22 and was diagnosed with the infection on June 27.

On Aug 11, the mother of a 6-year-old boy from Anhui province said her son had died from the same infection. He was suspected of being infected either while playing with water at his kindergarten in mid-June or while scooping fish by a riverbank in April.

Lu Yan, a researcher at the National Institute of Parasitic Diseases of the Chinese Center for Disease Control and Prevention, said the infection is caused by "brain-eating" amoebae — single-cell organisms that thrive in warm water such as lakes, rivers and hot springs, as well as in soil and mud.

The amoebae often enter the body through the nose or mouth when people swim, dive or play in freshwater, pools or other untreated water. They can invade the brain, destroy tissue and cause death.

Early symptoms include skin lesions, followed by fever, headache and vomiting.

"The disease can progress rapidly, and due to the lack of specific clinical symptoms, it may be misdiagnosed," Lu said.

"Although the infection is difficult to cure, there is no need to overreact because it is a rare parasitic disease and the incidence rate is very low," she said.

China has reported more than 40 cases over the years involving balamuthia mandrillaris, one of the most common brain-eating amoeba species.

Lu advised against swimming, washing faces or playing in water in wild ponds, lakes and rivers, as well as refraining from digging or stirring up sediments at the bottom of water bodies.

"It is also recommended to avoid submerging your head when swimming in freshwater, hot springs or other untreated warm water bodies," she said. "People with open wounds should avoid water activities or ensure proper protection before exposure to natural waters."

She stressed the importance of seeking prompt medical attention if headaches, fever or other symptoms occur after swimming or playing in natural water sources. Informing doctors about such activities can help confirm the diagnosis as early as possible.

"Early detection and treatment are key," she said.

Huang Lisu, head of the infectious disease department at the Children's Hospital affiliated with Zhejiang University's School of Medicine, told People's Daily that the disease's rapid progression, low incidence, limited diagnostic and treatment capacity at grassroots hospitals and the lack of targeted medications for infected children have compounded treatment challenges.

She noted that the hospital has successfully treated two patients in the past year and a half.