When tap water turns deadly: Multiple people diagnosed with dangerous amoeba after nasal rinsing

By Claire Wolters | Fact-checked by Davi Sherman
Published March 20, 2024

Key Takeaways

  • Tap water can be contaminated with pathogens like acanthamoeba, which can put people at risk of developing rare but serious infections.

  • Tap water can also be contaminated with heavy metals that can have worrisome neurological impacts.

  • Educating patients about tap water risks can help them make informed decisions about when to opt for tap versus sterilized water.

The Centers for Disease Control and Prevention (CDC) is warning about health risks from tap water, such as coming into contact with life-threatening waterborne pathogens like Acanthamoeba.[]

In an early-release study published in the CDC’s Emerging Infectious Diseases journal, researchers evaluated and discussed how tap water used for nasal rinsing may induce risks of non-keratitis Acanthamoeba. In the study, ten patients were diagnosed with non-keratitis Acanthamoeba following nasal rinsing, at least four of whom rinsed with tap water, the researchers wrote.

About acanthamoeba

Acanthamoeba is a free-living amoeba found in many different water sources, including tap water. The pathogen can cause Acanthamoeba keratitis, a rare but serious eye infection that infects the cornea and can, in some cases, lead to permanent vision loss or blindness. While the infection can damage the eye, it typically does not spread to other body parts. Acanthamoeba can also cause non-keratitis infections, which impact other parts of the body outside of the eye and can include conditions like granulomatous amebic encephalitis (GAE), cutaneous disease, rhinosinusitis, pulmonary disease, osteomyelitis, and disseminated infections, according to the CDC.[]

Acanthamoeba infections from tap water

When tap water is contaminated with Acanthamoeba, patients can be at risk of infection. According to the CDC, high-risk patients, including those who are immunocompromised from disease or medical treatments, are most at risk for non-keratitis Acanthamoeba infections.

Studies have also demonstrated that people who wear contact lenses may be at risk of keratitis Acanthamoeba infections if they rinse their contacts in contaminated water or frequently touch their eyes after rinsing their hands. Researchers hypothesized that “hand washing may release the microbial contaminants from fingernails and hand palms that might then lodge on the lenses when handled.”[]

Contaminated tap water may also have dangerous neurological impacts, particularly if it is overloaded with heavy metals. 

Claudia Zhang, a hydrologist who works with the water filter company Waterdrop, explains that “water contamination with heavy metals and organic compounds poses a health risk, particularly due to the neurotoxic effects of substances like lead, copper, arsenic, and certain synthetic organics.”

These compounds can be present in water at low concentrations, she adds, and “can potentially contribute to developmental issues, cognitive decline, and the exacerbation of neurodegenerative diseases.”

Importance of educating patients about tap water safety

Acanthamoeba risks are rare, but not as rare as some patients think, according to the CDC. A 2021 survey on misperceptions and use of tap water in the United States revealed that 33% of people incorrectly answered that tap water does not contain bacteria or living things; 50% of people said that tap water could be used for rinsing contact lenses; and 62% of people said that tap water could be used for nasal rinsing.[]

Tap water is not void of pathogens, and the CDC does not recommend that tap water be used—without first boiling it—for nasal or contact rinsing. To demonstrate Acanthamoeba’s presence in tap water, the CDC cited research conducted on household water in Ohio in the early 1990s, where the pathogen was present in water samples of over 70% of Ohio households.[]

Educating patients about tap water risks can help them make educated decisions on how to use their faucets. While doctors do not need to discourage patients from using tap water for other purposes like washing their hands, they should dispel rumors that tap water is completely safe and pathogen-free.

Educating patients about heavy metal contamination and the importance of sterilizing or filtering water for brain health may also be a good idea.

Zhang recommends that doctors “include environmental considerations in their patient assessments, particularly for individuals who might be exposed to contaminants in drinking water,” and “inform patients about the potential risks of neurotoxicity associated with exposure to waterborne contaminants like lead, copper, and organic chemicals, and advocate for regular water quality testing.”

Despite tap water risks, research continues to encourage handwashing with soap and water

Despite tap water’s risks, researchers and the CDC continue to recommend that people wash their hands with soap and water. Per the above study, the researchers say that they “still recommend hand washing with soap and water for removal of more pathogenic organisms.”

For nasal rinsing, the CDC recommends using boiled, sterile, or distilled water.[]

“All healthcare providers caring for immunocompromised persons should educate their patients about Acanthamoeba infections, including how to recognize symptoms and how to practice safe nasal rinsing,” researchers stated in Emerging Infectious Diseases journal. “Educating against the use of unboiled tap water for nasal rinsing may be effective in preventing invasive Acanthamoeba infections, particularly among immunocompromised hosts.”

What this means for you

Tap water can be contaminated with pathogens and/or heavy metals that pose health risks. Doctors should encourage patients to be wary of tap water risks and to avoid using unboiled tap water for health device purposes, such as nasal rinsing or cleaning contact lenses.

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