GRAPHICS
Infectious Diseases
Flesh-eating bacteria, brain-eating amoebas pose risks for swimmers
Janet LoehrkeUSA TODAY
July 17, 2026, 4:01 a.m. ET
For many people, a swim in a lake or river is the perfect way to escape the summer heat
But beneath the surface, the waters can contain more than fish and frogs. Microscopic organisms capable of causing severe illness and, in rare cases, death, may also be present
According to the Centers for Disease Control and Prevention, two waterborne pathogens have become increasingly common in U.S. freshwater lakes and brackish waters in recent years, a trend linked to rising water temperatures driven by climate change
The threat comes from two rare but potentially deadly pathogens: Vibrio vulnificus, often referred to as “flesh-eating bacteria,” and Naegleria fowleri, the “brain-eating amoeba.”
As of mid-June, eight cases of flesh-eating bacteria had been confirmed in Florida this year, according to the University of South Florida’s NPR. And the brain-eating amoeba was found in two of the United States’ most popular national parks, USA TODAY reported
How do these pathogens enter the body?
Both the brain-eating amoeba and flesh-eating bacteria flourish in warm water conditions
Brain-eating amoebas are more commonly found in warm freshwater lakes and rivers, while flesh-eating bacteria are primarily found in warm brackish water, which is a mix of fresh and salt water
Here’s how both pathogens can enter the body during water activities:
Why is it called a brain-eating amoeba?
The amoeba is often referred to as brain-eating because it can cause a deadly infection called Primary Amebic Meningoencephalitis (PAM) that destroys brain tissue
The brain-eating amoeba usually kills fewer than 10 Americans each year. In particular, only four survivors have been identified of the 167 instances that have been recorded in the United States “between 1962 and 2024,” according to the CDC
Why is it called flesh-eating bacteria?
The bacteria are often referred to as flesh-eating because they can cause necrotizing fasciitis, which destroys muscle tissue, skin tissue, and skin. It can enter through a cut, but it cannot penetrate unharmed skin
The bacteria can also enter your body when you eat uncooked or undercooked shellfish
The flesh-eating bacteria are rare, but they can be life-threatening. Without treatment, death can occur in just a few days
An average of 150 to 200 cases is reported each year, with most in Gulf Coast states, according to the CDC
Take precautions during water activities
Swimmers, particularly those in southern states and warm coastal waters, should expect a minimal risk of contracting a pathogen in warm freshwater lakes, rivers, brackish waters, and hot springs
Here’s how to lower your risks:
Medical experts always recommend keeping a close eye on children when they play or swim in the water. While it’s uncommon for adults to swallow water while swimming, children are far more prone to do so, according to VCU Health
Researchers are unsure why boys appear to be most at risk of being infected. It may be because they are more prone to play in the sediment at the bottom of lakes or jump and dive into the water, according to the CDC
Progression of infection: Know the symptoms
Because of the life-threatening results, it is important to be aware of symptoms and the significance of seeking immediate medical assistance following any exposure
Here is a comparison of symptoms of the flesh-eating bacteria and the brain-eating amoeba:
CONTRIBUTING Julie Garisto, T. Sudore, and C.A. Bridges, USA TODAY NETWORK; Christopher Cann and George Petras, USA TODAY
