Fatal Amoeba Brain Infection Linked to Tap Water in a Nasal Rinser and CPAP Machine

Acanthamoeba is a group of free-living amoebas that can cause severe disease of the brain, eyes, sinuses, skin and other organs, mostly in people with weakened immune systems. In the United States, roughly three to 12 people a year get Acanthamoeba infections other than keratitis, and most of them die. Because the amoeba is everywhere in the environment and its incubation period is unknown, possibly weeks or months, the source of an infection is usually never found.

A case series of ten patients with weakened immune systems had found that all of them used nasal irrigation before falling ill, many with tap water, but no environmental testing confirmed that route. This case did.

The case

On November 15, 2023, CDC learned of a 66-year-old patient who had died about three weeks after being hospitalized with confusion and weakness. The illness worsened to include seizures, fever, and breathing and digestive complications. Magnetic resonance imaging showed brain lesions, and the autopsy found signs of granulomatous amebic encephalitis.

The patient reported no recent recreational water exposure but regularly used tap water in an electronic nasal irrigation device and a continuous positive airway pressure (CPAP) machine at home. How the devices were cleaned is not known. The patient had diabetes, obstructive sleep apnea, alcohol use disorder, and ulcerative colitis that had required removal of the entire colon.

The evidence

• On January 4, 2024, working with the New Mexico Department of Health, CDC received brain tissue and confirmed Acanthamoeba encephalitis by immunohistochemistry and PCR.
• Acanthamoeba was also grown from the nasal irrigation device and from the drained water reservoir of the CPAP machine, and confirmed by real-time PCR on February 5.
• Every strain belonged to genotype T4, the one most often found in encephalitis cases.

Photos/Infectious Disease Pathology Branch, CDC.

This investigation confirms that tap water in the nose can cause Acanthamoeba infection. Poor cleaning and drying may have contributed: some of these devices have parts that are hard to reach for proper cleaning and drying.

How to protect yourself

• For nasal irrigation, use distilled, sterile, or boiled and cooled tap water.
• Follow the manufacturer's instructions on what water to use and how to clean electronic medical devices such as CPAP machines, and on cleaning nasal irrigation devices.

The authors urge clinicians to talk with patients about Acanthamoeba and safe water for these devices, and to report cases to local or state health officials, who in turn are asked to report them to CDC. CDC runs a free-living ameba consultation service for clinicians 24 hours a day, 7 days a week, offering advice on diagnosis and treatment.

Sources

• Haston JC, Ali IK, Roy S, et al. Notes from the Field: Fatal Acanthamoeba Encephalitis in a Patient Who Regularly Used Tap Water in an Electronic Nasal Irrigation Device and a Continuous Positive Airway Pressure Machine at Home — New Mexico, 2023. MMWR Morb Mortal Wkly Rep 74(10). https://www.cdc.gov/mmwr/volumes/74/wr/mm7410a4.htm
• CDC, preventing waterborne germs at home: https://www.cdc.gov/drinking-water/prevention/preventing-waterborne-germs-at-home.html
• The report was written jointly by CDC, the New Mexico Department of Health and the University of New Mexico; its laboratory figure is not reproduced here. Pictures an earlier version of this page left out were restored on 2026-09-26.