Sources of Infection & Risk Factors

Acanthamoeba keratitis

Acanthamoeba keratitis is a rare disease that can affect anyone, but is most common in individuals who wear contact lenses. In the United States, an estimated 85% of cases occur in contact lens users. The incidence of the disease in developed countries is approximately one to 33 cases per million contact lens wearers.

For people who wear contact lenses, certain practices can increase the risk of getting Acanthamoeba keratitis:

• Storing and handling lenses improperly
• Disinfecting lenses improperly (such as using tap water or topping off solutions when cleaning the lenses or lens case)
• Swimming, using a hot tub, or showering while wearing lenses
• Coming into contact with contaminated water
• Having a history of trauma to the cornea

Contact lens wearers who practice proper lens care and non-contact lens wearers can still develop the infection. For additional information on contact lens care and prevention of Acanthamoeba keratitis visit CDC’s web page on Prevention and Control.

There have been no reports of Acanthamoeba keratitis being spread from one person to another.

Granulomatous Amebic Encephalitis (GAE)

Granulomatous Amebic Encephalitis (GAE) and disseminated infection are very rare forms of Acanthamoeba infection and primarily affect people with compromised immune systems. While unusual, disseminated infection can also affect healthy children and adults. Conditions that may increase a patient’s risk for GAE and disseminated infection include:

• AIDS
• Organ/Tissue transplant
• Steroids or excessive use of antibiotics
• Diabetes Mellitus
• Cancer
• Disorders in which white blood cells in the lymphatic tissue are over-produced or abnormal
• Disorders in which blood cells or blood clotting mechanisms do not function properly or are abnormal
• Liver cirrhosis
• Lupus