An 8-year-old Louisiana girl has died after being infected with Naegleria fowleri, an extremely rare "brain-eating amoeba" found in warm freshwater, according to her family.

Lillian Smart died over the weekend after being diagnosed with the infection, a spokesperson for her family said. Health authorities describe Naegleria fowleri as an organism that thrives in freshwater bodies across the United States and can travel up the nose, triggering an infection that almost always proves fatal. On average, fewer than 10 cases are recorded annually in the U.S.

The amoeba "grows best" during extended periods of extreme heat and lower water levels, the Louisiana Department of Health said in a separate release announcing the case — conditions that have persisted across the Gulf South this summer.

"Last night Lillian ran from our arms to the arms of Jesus," her parents, Daniel and Rebecca Smart, wrote Sunday in a public Facebook post. "The injuries to her brain were too severe for her little body to recover from. Everyone did everything they could to keep her here."

Louisiana's first confirmed case since 2013

The state health department said last week that Louisiana had recorded its first confirmed Naegleria fowleri infection since 2013. The department, which did not identify Smart, does not comment on individual cases or specific patients, spokesperson Stacey Grow said.

"Heartbroken over the news of Lillian's passing," Louisiana Gov. Jeff Landry wrote on X.

The infection was likely contracted while swimming in Lake Claiborne in north Louisiana, the department said.

When water carrying the amoeba travels up the nose and into the brain, it can cause a fatal infection known as primary amoebic meningoencephalitis. Between 1937 and 2025, only about 180 confirmed infections have been documented in the U.S., and the Health Department described such cases as "nearly always fatal." The infection cannot spread from person to person.

Part of what makes the infection so lethal is how it first presents: early symptoms such as severe headache, fever, nausea and vomiting can resemble bacterial meningitis, and the illness typically worsens within days, so cases are rarely confirmed in time to treat. The CDC has documented only a small number of U.S. survivors, most of whom were diagnosed early and treated aggressively.

A warm-water organism

Naegleria fowleri is found in warm freshwater lakes, rivers, canals, and ponds throughout the United States. The amoeba becomes dangerous in water that remains above 77 degrees Fahrenheit (25 degrees Celsius), and for years it has been documented almost exclusively during the summer in the southern part of the country. Scientists said a few recent cases have appeared in Maryland, Indiana, and Minnesota.

"The amoeba is naturally occurring, and there is no routine environmental test for Naegleria fowleri in bodies of water," the Louisiana Department of Health stated.

With no test to flag contaminated water, prevention is the main safeguard. The CDC advises people in warm freshwater to hold their noses shut, use nose clips, or keep their heads above water; to avoid water activities during periods of high water temperature and low water levels; and to refrain from digging in or stirring up sediment, where the amoeba can concentrate. It also recommends using only distilled, sterile, or previously boiled water for sinus rinsing — improperly treated tap water has been linked to earlier infections, including two Louisiana deaths in 2011 tied to nasal rinsing.

Last year, a 12-year-old boy in South Carolina also died from an infection caused by the amoeba.

Additional reporting was contributed by Nick Lichtenberg.

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Brook is a corps member of The Associated Press/Report for America Statehouse News Initiative. Report for America is a nonprofit national service program that places journalists in local newsrooms to report on undercovered issues.

Source: Fortune