Naegleria fowleri is a free living amoebaflagellate that resides in warm freshwater environments from lakes and rivers to geothermal wells and, rarely, domestic tap or RV water systems. It causes primary amebic meningoencephalitis, a rapidly progressing and almost invariably fatal brain infection.

Until recently, most attention focused on risks from swimming in lakes or rivers. But new evidence has highlighted another route of exposure: nasal irrigation using non sterile tap water, including water from RV hookups.

A recent case that raised alarm

In mid 2025, the CDC documented the first known US fatal case of PAM linked to nasal irrigation using tap water from an RV system at a Texas campground. The patient, a previously healthy 71 year old woman, used an irrigation device filled with that water. Four days later she developed fever, headache, confusion, and seizures. Eight days after symptoms began, she died despite hospitalization. Although the amoeba was not isolated from the water due to delayed sampling, investigators concluded the water was inadequately disinfected and nasal irrigation was the probable source.

In response, the CDC urged people never to use tap water for nasal cleansing unless it has been boiled for at least one minute (three minutes at high altitude), cooled, or is certified sterile or distilled. Authorities also stressed the importance of keeping irrigation devices and RV water systems clean to prevent hidden risks.

How the infection occurs

While pathogens in drinking water rarely cause illness when swallowed, water entering through the nose bypasses many natural defenses. Naegleria fowleri can travel along the olfactory nerve into the brain, where it multiplies and feeds on neural tissue, causing necrotizing meningoencephalitis. With a fatality rate near 99 percent, only a handful of survivors have ever been recorded.

Globally, about 9 percent of PAM cases have involved nasal irrigation as the only known exposure. Most other cases come from recreational water activities. The Texas case is the first documented US death tied to RV derived tap water, making this route of exposure a critical focus.