Last updated: June 20, 2025
Source: Centers for Disease Control and Prevention

Key Points

Acanthamoeba is a free-living ameba, a type of one-celled organism that lives in water, soil, and dust.
Most people will come into contact with Acanthamoeba at some point, but most will not get sick.
Although rare, some people develop serious Acanthamoeba infections that can be life-threatening.
Seek medical care immediately if you experience symptoms of an Acanthamoeba infection.

Overview

Most people will be exposed to Acanthamoeba during their lifetime. This microscopic ameba is found in:

Soil and dust
Fresh water and saltwater
Swimming pools and hot tubs
Drinking water systems
Humidifiers
Heating, ventilation, and air conditioning (HVAC) systems

How Infection Occurs

Most people exposed to Acanthamoeba do not become ill. However, infection can occur when the ameba enters the body through:

Cuts or open wounds on the skin
Inhalation into the lungs or nostrils
Contact with the eyes, particularly through contact lens use

When infection does occur, Acanthamoeba can cause serious illnesses affecting the brain, skin, eyes, and sinuses.

Types of Acanthamoeba Infections

Non-Keratitis Acanthamoeba Infections

Non-keratitis Acanthamoeba infections are rare but serious conditions that can affect one or multiple parts of the body. These infections typically occur in people with weakened immune systems.

Infection Type	Description	Severity
Granulomatous Amebic Encephalitis (GAE)	Infection of the brain and spinal cord	Nearly always fatal
Cutaneous Acanthamoebiasis	Skin infection, often presenting as nodules, ulcers, or abscesses	Serious; can disseminate
Acanthamoeba Rhinosinusitis	Infection of the nasal cavity and sinuses	Serious; can spread to brain
Disseminated Infection	Infection affecting multiple organ systems	Life-threatening

GAE, cutaneous acanthamoebiasis, and Acanthamoeba rhinosinusitis can all progress to disseminated infection if not promptly diagnosed and treated.

Acanthamoeba Keratitis

Acanthamoeba keratitis is a rare but severe eye infection that typically occurs in otherwise healthy individuals.

Key Characteristics

Primarily affects contact lens wearers in the United States
Can cause permanent vision loss or blindness if not treated early
Usually does not spread to other parts of the body
Symptoms may include eye pain, redness, blurred vision, light sensitivity, and the sensation of something in the eye

Risk Factors for Contact Lens Wearers

Using tap water to clean or store contact lenses
Swimming, showering, or using hot tubs while wearing contact lenses
Not following proper lens hygiene and disinfection protocols
Wearing lenses longer than recommended

Free-Living Amebas

A free-living ameba is a single-celled organism that lives independently in water and soil environments worldwide. Most people encounter these organisms without developing illness. However, a small number of individuals may develop rare but serious infections.

Amebas Known to Cause Severe Human Disease

Ameba	Primary Infections	Typical Exposure Routes
Acanthamoeba	Brain (GAE), skin, sinuses, eyes (keratitis)	Water, soil, dust; contact lens use
Balamuthia mandrillaris	Brain (GAE), skin	Soil, dust; inhalation or skin wounds
Naegleria fowleri	Brain (primary amebic meningoencephalitis)	Warm freshwater entering the nose

All three amebas can cause life-threatening brain infections. Some can also cause infections of the eyes, skin, sinuses, and other body sites.

When to Seek Medical Care

Consult a healthcare provider immediately if you experience symptoms that may indicate an Acanthamoeba infection, especially if you:

Wear contact lenses and develop eye pain, redness, or vision changes
Have a weakened immune system and develop unexplained skin lesions, neurological symptoms, or sinus issues
Have had recent exposure to contaminated water or soil and develop concerning symptoms

Early diagnosis and treatment are critical for improving outcomes in Acanthamoeba infections.

Related Resources

For the Public

For Healthcare Providers

Clinical Overview of Acanthamoeba Infections
Diagnostic Guidelines for Non-Keratitis Infections
Treatment Recommendations and Case Management

About CDC's Work on Acanthamoeba

CDC monitors, investigates, and provides guidance on Acanthamoeba infections to:
- Improve detection and diagnosis of rare amebic infections
- Support healthcare providers with clinical resources and consultation
- Educate the public, especially contact lens wearers, on prevention strategies
- Conduct research to better understand transmission, risk factors, and treatment outcomes

This content is adapted from the official CDC website. For the most current information, please visit cdc.gov/parasites/acanthamoeba.