Sinus Rinse Warning: Tap Water Linked to Deadly Brain-Eating Amoeba Infections in New Medical Study

In a breakthrough study published in a medical journal, U.S. researchers have investigated an unusual source of severe infection among immune-compromised people: nasal rinsing. This seemingly benign hygiene habit, often endorsed for its health benefits in clearing sinuses and relieving chronic sinusitis symptoms, may pose a severe risk when tap water contaminated with Acanthamoeba—a type of free-living amoeba—is used.

The study in question describes ten patients who contracted nonkeratitis Acanthamoeba infection after performing nasal rinsing with tap water. The patients were all immune-compromised, with most of them suffering from chronic sinusitis and other health conditions such as cancer (particularly hematologic cancers like chronic lymphocytic leukemia), HIV/AIDS, or diabetes mellitus. It's important to highlight that although such infections are quite rare, with only a few documented cases each year in the U.S., a staggering 82% are typically fatal.

What is Acanthamoeba, and why is it dangerous? Acanthamoeba are tiny, one-celled organisms that are usually harmless. They inhabit various environments including soil, rivers, lakes, and even the tap water in our homes. While these amoebas can cause a painful eye infection known as keratitis, they are also capable of causing far more severe infections like granulomatous amebic encephalitis (GAE), which affects the central nervous system, along with skin diseases, rhinosinusitis (nasal and sinus inflammation), lung disease, bone infections (osteomyelitis), and more widespread, or disseminated, diseases.

The threat is particularly acute for individuals with compromised immune systems. People who've had organ or stem cell transplants, are undergoing cancer treatment, living with HIV/AIDS, or have diabetes are at a higher risk of being infected by this opportunistic pathogen. Acanthamoeba enter the body through various routes: when we get dirt in our eyes, suffer skin injuries, or through our respiratory tracts.

This CDC-backed study uncovered a possible transmission route of Acanthamoeba through the practice of nasal rinsing. Nasal rinsing, or nasal irrigation, is a common practice in various cultures and religions, and it's typically recommended for health benefits. Devices used for nasal rinsing include neti pots, squeeze bottles, or even just cupped hands. However, the researchers found that if the water used for rinsing isn't sterile, it can introduce harmful pathogens into the body.

How prevalent is the misunderstanding about tap water's safety in nasal rinsing? Surprisingly, recent studies suggest that nearly two-thirds of U.S. adults believe that tap water is safe for this purpose. Yet, using tap water for nasal rinsing has been associated with deadly infections caused by organisms like Naegleria fowleri and Acanthamoeba.

The researchers used the CDC's free-living amoeba database to identify patients with laboratory-confirmed nonkeratitis Acanthamoeba infections who had a history of nasal rinsing. Nine out of the ten cases occurred in the past decade, with the patients' median age being 60 years. Notably, this study discovered a higher-than-expected survival rate among its subjects. Seven of the ten patients survived their infection, which is remarkable given the typically high fatality rates. Diagnoses were predominantly made using PCR (polymerase chain reaction), a method that allowed for rapid detection of the infection.

When looking at the clinical manifestations, a majority of the patients had rhinosinusitis, skin disease, and nearly half had central nervous system involvement, signifying GAE. Cutaneous disease and osteomyelitis were other complications observed. The study also found that the dissemination of the amoeba to other organ systems might have been facilitated by a delay in recognizing acute sinus symptoms, especially in patients with a background of chronic sinusitis.

One of the key findings lays in the survival rate: patients presenting early with skin or sinus manifestations survived at higher rates because treatment could begin sooner. Among those with GAE, a condition previously associated with less than a 7% survival rate, half of the patients in this study survived. Some survivors presented with skin lesions before any central nervous system symptoms appeared, which may have led to earlier treatment and better outcomes.

The nasal rinsing practices of the patients varied: some did it as part of a religious ritual, others for relief from chronic sinusitis. At least four of the patients used unsterilized tap water, and one patient reported using sterile water but then exposed the rinsing device to tap water. The other five patients did not report the type of water they used. The frequency of nasal rinsing among the patients varied greatly, from once per week up to five times per day, with the development of symptoms occurring after periods ranging from a couple of weeks to several years.

The researchers' conclusions from these ten cases highlight nasal rinsing with tap water as a potential transmission route for invasive Acanthamoeba infections. This study underscores the need for heightened awareness and education about safe nasal rinsing practices, especially among those who are immune-compromised.