Louisiana state health officials are warning patients about potential dangers of using tap water in the sinus-irrigating neti pot after two patients died of Naegleria fowleri infection.

N. fowleri is known as a "brain-eating" amoeba because it can enter a patient's nose, infect the brain, and cause primary amebic meningoencephalitis (PAM), a brain-tissue destroying condition.

The first Louisiana patient died of neti pot-induced infection in June. An additional two patients died of N. fowleri infection in August after swimming in warm, fresh water.

The amoeba usually infects patients that submerge their heads in freshwater lakes and rivers, though it can be transmitted through inadequately chlorinated pool water or underheated (less than 116°F) tap water that enters a patient's nose, a statement from the Louisiana Department of Health and Hospitals said.

Patients that irrigate their noses with a neti pot should use distilled, sterile, or previously boiled water, Raoult Ratard, MD, a Louisiana state epidemiologist, said in the statement. He noted that tap water was safe to drink, but may not be safe for nasal cleansing.

Symptoms of PAM include headache, fever, nausea, vomiting, and stiff neck, and may take one to seven days to start. Later symptoms include confusion, lack of attention to environment, loss of balance, seizures, hallucinations, and, in one to 12 days after infection, death. The disease progresses rapidly and symptoms may resemble bacterial meningitis, the statement warned.

N. fowleri infection is rare in the U.S. -- only 32 cases have been documented from 2001 to 2010, according to the CDC website. The agency also noted that patients should rinse devices like the neti pot after use and to allow it to air dry.

The CDC is actively working with Louisiana state health officials on the investigation, an agency representative told MedPage Today.