Scientists are sounding the alarm over a little-known but potentially deadly group of microorganisms that may be quietly spreading through water systems around the world. Environmental and public health researchers have warned that free-living amoebae, resilient microbes found naturally in soil and water, are emerging as a growing global health concern due to climate change, weakening water infrastructure and limited monitoring systems.
In a recent perspective published in the journal Biocontaminant, researchers highlighted how these microscopic organisms are capable of surviving in environments that typically eliminate other harmful microbes. While most amoebae are harmless, a small number can cause severe and often fatal infections in humans. Among the most dangerous is Naegleria fowleri, commonly known as the brain-eating amoeba, which can trigger a rare but rapidly progressing brain infection called primary amoebic meningoencephalitis.
The infection occurs when contaminated water enters the body through the nose, usually during activities such as swimming or diving in warm freshwater. Although cases remain rare, the disease is almost always fatal, making even limited exposure a serious public health concern.
Researchers say what makes free-living amoebae particularly dangerous is their extraordinary ability to survive harsh conditions. These organisms can tolerate high temperatures, withstand disinfectants such as chlorine and persist inside water distribution systems that are widely assumed to be safe for human use. According to the scientists, this resilience allows amoebae to remain undetected in drinking water networks and recreational water sources for extended periods.
Beyond causing infections directly, amoebae pose another hidden threat. They can act as protective hosts for other dangerous microbes, including bacteria and viruses. By sheltering these pathogens inside their cells, amoebae help them evade disinfection processes and spread more easily through water systems. This so-called Trojan horse effect may also play a role in the spread of antibiotic-resistant bacteria, further complicating public health efforts.
Climate change is expected to intensify the risk. Rising global temperatures are expanding the geographic range of heat-loving amoebae into regions where they were previously uncommon. Scientists note that recent outbreaks linked to recreational water use in several countries may be early signs of a much broader problem.
The authors of the study stress that tackling this threat requires a coordinated One Health approach that brings together human health experts, environmental scientists and water management authorities. They have called for stronger surveillance systems, improved diagnostic tools and the adoption of advanced water treatment technologies to detect and control amoebae before infections occur.
Researchers warn that free-living amoebae cannot be viewed solely as a medical or environmental issue. Instead, they represent a complex challenge at the intersection of climate change, public health and infrastructure management. Without integrated solutions and proactive investment in water safety, scientists caution that these invisible pathogens could pose an increasing risk to communities worldwide.