Deadly Bacteria Came From Tap Water

Two fatal cases of primary amoebic meningoencephalitis (PAM) in Louisiana are the first recorded instances of PAM in the United States involving Naegleria fowleri in household plumbing with municipally treated tap water.

These cases also represent the first time nasal irrigation devices have been associated with instances of PAM.

Symptoms of PAM include headache, fever, stiff neck, anorexia, vomiting, altered mental state, and seizures, with onset occurring anywhere between 1 to 7 days after exposure.

In the first case, a 28-year-old man developed severe occipital headache, neck stiffness, back pain, confusion, and fever. 

"The patient had chronic allergic sinusitis and irrigated his sinuses with a neti pot at least once daily, using tap water to which he added a commercially available salt packet," wrote Jonathan Yoder, MPH, of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases in Atlanta, and colleagues. 

Samples from the patient’s home revealed several amoebae, and water from a tankless water heater was positive for N. fowleri.  The neti pot tested negative for N. fowleri, although finding viable samples within a dry neti pot was unlikely, the authors said. 

A 51-year-old woman who developed altered mental status, nausea, listlessness, fatigue, neck stiffness, and high fever presented as the second case.  She also used a neti pot to treat sinus problems.  Samples taken from the woman’s kitchen faucet, shower, and bathroom sink all tested positive for N. fowleri.

In both cases, identification of PAM occurred after treatment was no longer possible – after declaration of brain death in the first case, and during the autopsy in the second. 

Both municipal water sources tested negative for N. fowleri.  The authors were uncertain how the amoeba was able to colonize household hot water systems, suggesting a possible relation to the upward shift of thermophilic amoeba from the southern United States due to heat waves.

"It is unclear whether the increased temperature and heat waves projected in climate change models will lead to further expansion of the [amoeba's] geographic range," they said.

-Michael Potts


Yoder J, Straif-Bourgeois S, Roy S, et al. Primary Amebic Meningoencephalitis Deaths Associated With Sinus Irrigation Using Contaminated Tap Water [published online ahead of print August 22, 2012]. doi: 10.1093/cid/cis626