A Missouri resident is in intensive care after contracting a rare brain-eating amoeba, likely while water skiing at the Lake of the Ozarks, state health officials confirmed Wednesday.

The case of Naegleria fowleri — the scientific term for the amoeba — marks another confirmed U.S. infection this summer after a case in South Carolina and underscores the growing concern about these deadly organisms in warm freshwater across the country.

The Missouri Department of Health and Senior Services said preliminary information suggests the patient may have been water skiing at the Lake of the Ozarks days before becoming ill. It’s only the third confirmed case in Missouri since 1962, with previous cases reported in 1987 and 2022.

The Missouri Department of Health and Senior Services said the source of the patient’s exposure is being investigated by public health officials. 

“Recreational water users should assume that Naegleria fowleri is present in warm freshwater across the United States; however, infection remains very rare,” officials said.

No other suspected cases are being investigated in Missouri at this time.

The amoeba can be found in warm freshwater but occasionally has been detected in tap water. Health agencies stress that infections are extremely rare, with fewer than 10 cases annually in the U.S. However, those cases are usually deadly.

Because the amoeba occurs naturally, there is no way to prevent it in lakes or rivers. The amoeba is only life-threatening if it goes up the nose and travels to the brain. It is not deadly if ingested through the mouth.

The CDC says early symptoms of the amoeba infection include fever, headache, nausea and vomiting. Cases usually progress rapidly.

Naegleria fowleri, often referred to as the brain-eating amoeba, is a rare organism that can infect humans through unfiltered water, often with deadly results.

The bacteria causes primary amebic meningoencephalitis, or PAM, a brain infection that is almost always fatal. Between 1962 and 2024, only four people in the U.S. out of 167 known cases have survived, according to health officials.

The amoeba is typically found in warm freshwater environments like lakes, rivers, hot springs and poorly chlorinated swimming pools. When contaminated water enters the nose, it can travel to the brain and cause severe inflammation.

Naegleria fowleri can only be diagnosed positively through laboratory tests, which are available in only a few labs in the U.S. Because they’re incredibly rare and difficult to test for, many cases aren’t diagnosed until after the patient has died.

The Missouri case comes as researchers warn that climate change is creating conditions for more frequent infections.

The amoeba thrives in temperatures between 80 and 115 degrees, which is outside the livable range of competing microorganisms. Lakes and rivers are becoming hotter due to climate change, and stronger storms are increasing the amount of organic matter that ends up in waterways through flooding, creating ideal conditions for Naegleria fowleri populations to spike.

State health departments monitor water sources for the deadly bacteria, which is found around the world. According to the Minnesota State Health Department, infections are mainly discovered during the summer months of July, August and September because hot weather means higher water temperatures and lower water levels.

Earlier this summer, a fatal case of brain-eating amoeba was confirmed in South Carolina involving a 12-year-old. Two weeks after Jaysen Carr spent the Fourth of July swimming and riding on a boat on one of South Carolina’s most popular lakes, he was dead from the amoeba.

In June, the CDC confirmed that the 2024 death of a 71-year-old woman in Texas was caused by a brain-eating amoeba. The woman developed severe symptoms just four days after using a nasal irrigation device filled with tap water from an RV’s water system at a Texas campground.

According to a CDC report, the woman experienced fever, headache and altered mental status before progressing to seizures. Despite medical care, she died eight days after her symptoms began.

Louisiana, which has numerous warm and shallow waterways because of its proximity to the gulf and marshy terrain, has had numerous reports over the past decade where health officials found samples of Naegleria fowleri in the state’s public water systems.

A 2023 study found that higher water temperatures caused by climate change were contributing to the rise in flesh-eating bacteria found in the state’s water systems.

In 2021, the CDC released a map showing locations across the U.S. where the amoeba had been found through the years. That map showed exposures in 20 states, mostly in the southern U.S. According to the Wayback Machine, which archives older versions of web pages, the CDC removed the map sometime in 2024.

Chris McCrory contributed to this report.