The U.S. Centers for Disease Control and Prevention (CDC) has renewed its warning against using tap water for nasal irrigation, as a newly published investigation linked the practice to infections of a deadly amoeba.
Acanthamoeba can cause keratitis, which is an infection of the eye that does not spread to other parts of the body, according to the report. However, they can also cause a variety of severe human infections, including granulomatous amebic encephalitis (GAE)—an infection causing severe inflammation of the brain and spinal cord, typically in those with a compromised immune system.
All ten patients were already immunocompromised. They also all reported performing nasal rinsing before becoming ill. Six patients were diagnosed with GAE, and three of them died.
Seven patients reported nasal rinsing for relief of chronic sinusitis symptoms, while two other patients did it as part of a cleansing ritual, the researchers noted. At least four patients said they used tap water, in addition to one patient who reported using sterile water after submerging their device in tap water.
Over the years since the first acanthamoeba infection was diagnosed in 1956, scientists have tried to find out exactly how people become infected. After examining patient cases in the recent decades, the CDC said the combination of unsanitary tap water and habitual nasal rinsing is likely to be blamed for the problem.
“In these 10 case-patients with invasive Acanthamoeba infection, nasal rinsing may have been the transmission route,” the researchers wrote in the report. “Duration and frequency of nasal rinsing behaviors varied, but most patients had been rinsing for months or even years.”
The CDC scientists also highlighted the fact that at least half of the ten patients in this case series used tap water in their nasal rinsing practices.
While two-thirds of Americans believe tap water is bacteria-free and safe to use to irrigate their sinuses, studies have found “acanthamoeba and other biofilm-associated amebae have been detected in over 50 percent of U.S. tap water samples,” they warned.
Safe Nasal Rinsing Practices
The practice of nasal rinsing, if done wrong, could also increase the risk of contracting naegleria fowleri, a different type of organism commonly referred to as “brain-eating amoeba.”Naegleria fowleri infects people when water containing the amoeba enters the body through the nose. This typically happens when people go swimming, diving, or when they put their heads under fresh water, like in lakes and rivers. The ameba, also spelt amoeba, then travels up the nose to the brain, where it can destroy brain tissue and cause a devastating infection called primary amebic meningoencephalitis (PAM).
PAM is almost always fatal. According to the CDC, of 157 people known to be infected with Naegleria in the United States from 1962 through 2022, only four have survived.
To reduce infection risk from dangerous amebae during nasal rinsing, the CDC recommends using treated water.
“It is safest to use boiled, distilled, sterile, or filtered water,” the federal agency advised, adding that when tap water is used, it should be boiled for a minimum of one minute, or three minutes at elevations above 6,500 feet, and left to cool before use.
One can also treat the water using a filter designed to remove common germs. Labels that read “NSF (National Sanitation Foundation) 53” or “NSF 58,” or contain the words “cyst removal” or “cyst reduction,” indicate that the filter can remove Naegleria.
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