A team of environmental and public health scientists is raising concerns about free-living amoebas, a largely overlooked group of microorganisms that may pose an increasing risk around the world. In a recent perspective article published in biological contaminantsresearchers explain that these tiny life forms are becoming a new global health risk. Their spread is being facilitated by rising temperatures, aging water infrastructure, and limited systems to detect and track them.
Most people have never heard of free-living amoebas, but scientists say they deserve more attention.
What is a freely living amoeba?
Amoebas are single-celled organisms that naturally live in soil, freshwater, and even man-made water systems. They move and feed by expanding part of their cell body. This process creates a unique shape.
Most amoebas are harmless and play a role in natural ecosystems. However, a small number of species can infect humans and cause serious illness. Although these infections are rare, they can be very serious when they occur.
One of the most well-known examples is Naegleria fowleri (often called the brain-eating amoeba). This microorganism can enter the body when contaminated water comes up to the nose, such as when swimming in warm lakes or poorly treated water. Once inside the body, it can reach the brain and cause a rapidly progressing infection that is almost always fatal.
Why these microorganisms are so difficult to eliminate
Scientists say one of the most worrying characteristics of these amoebas is their ability to withstand harsh conditions that would normally kill other microorganisms.
“What makes these organisms particularly dangerous is their ability to survive conditions that kill many other microorganisms,” said corresponding author Longfei Xu of Sun Yat-sen University. “They can withstand high temperatures and powerful disinfectants such as chlorine, and can even live in water distribution systems that people think are safe.”
This resilience means that standard water treatment methods may not always be sufficient to remove them, especially in older or poorly maintained systems.
The hidden role of amoebas in the spread of other pathogens
The risks go beyond the amoeba itself. The researchers highlight that these microorganisms can act as protective hosts for other harmful microorganisms, such as bacteria and viruses.
Inside the amoeba, these pathogens can survive in a kind of safe shelter, protected from disinfectants that would normally destroy them. This process is often described as the so-called Trojan horse effect. This allows dangerous microorganisms to remain in the drinking water system and spread more easily.
Scientists also worry that this protective environment could foster antibiotic resistance, making infections harder to treat over time.
Climate change is expanding their influence
The problem is expected to worsen as global temperatures rise. Many of these amoebas thrive in warm conditions, so as water temperatures rise, they can spread to new areas where they were once rare.
In recent years, several epidemics related to recreational water use have already raised public concerns in various parts of the world. These incidents suggest that the risk is no longer limited to a few isolated areas.
Demanding better monitoring and safer water systems
To address the growing threat, researchers are calling for a broader and more coordinated response. They recommend a One Health approach that brings together experts in human health, environmental science, and water management to approach problems from multiple angles.
Improving surveillance systems is a key priority, along with developing faster and more accurate diagnostic tools. The research team also highlights the need for advanced water treatment technologies that can better target these resilient organisms before they pose a risk to the public.
Problems that cross boundaries
“Amoebas are not just a medical or environmental problem,” Shu says. “They sit at the intersection of both, and addressing them requires integrated solutions that protect public health at its source.”
As scientists continue to study more of these microbes, one message is becoming clear: something nearly invisible to the naked eye may have a far greater impact on global health than previously thought.
