The Missouri resident had visited the beach at the Lake of Three Fires in Taylor County, Iowa, which has since been closed by authorities.
The amoeba, known as Naegleria fowleri, is a single-celled organism that lives in warm freshwater and can infect swimmers by traveling through the nose and into the brain. It causes an almost universally fatal infection, according to the US Centers for Disease Control.
Of the 154 known cases in the US over the last six decades, only four people have survived.
“Because these cases are so incredibly rare and out of respect for the family, we do not intend to release additional information about the patient which could lead to the person’s identification,” said the Missouri Department of Health and Senior Services.
Officials are currently testing samples from the lake for the presence of the amoeba.
While one drug has recently shown potential in fighting the infection, there isn’t necessarily a confirmed effective treatment process yet, the agency added.
The amoeba cannot be contracted through drinking, from a properly disinfected swimming pool or from one person to another, the CDC says.
Iowa DPH recommends holding your nose while in warm freshwater and avoiding freshwater when it gets particularly warm out.
Cases of “brain-eating” amoebas may be spreading northwards due to the climate crisis.
A 2021 study found that while the number of cases in the US has stayed mostly consistent since 1978, more and more cases are showing up further north and in places like Midwest — as opposed to the amoeba’s typical range in the southeast corner of the country.
Officials say that anyone who experiences severe headaches, fever, nausea, vomiting, stiff neck, seizures, altered mental health status, or hallucinations, should contact their healthcare provider immediately.