Only distilled or sterile water should be used when irrigating the sinuses, the Missouri health department said today in an alert following the deaths of two people in Louisiana.

The deaths were caused by an organism called Naegleria fowleri that can lead to a brain infection called primary amebic meningoencephalitis. Both people had used tap water to flush water through their noses with a device known as a neti pot.

The organism travels to the brain through the nose, destroying tissue as it goes. It can not cause an infection by drinking water through the mouth.

The water in St. Louis city is treated well beyond what's required by statute, a process that "should assure that the residual chlorine throughout the treatment system will destroy any Naegleria fowleri," according to a city health spokesman.

Representatives for the St. Louis County health department could not be reached.

The infections can occur when people swim in fresh water lakes and rivers and inhale water up their noses. In rare cases the cause has been linked to untreated swimming pools or tap water.

The symptoms of infection, which typically occur within a week of exposure, include headache, vomiting, fever, nausea and stiff neck and can progress to loss of balance, confusion, hallucinations and seizures. The disease is usually fatal within two weeks.

There are about three cases of Naegleria fowleri infections a year in the U.S. according to the Centers for Disease Control and Prevention. Nearly all were caused by contaminated water in lakes, streams or rivers. 

Louisiana health regulators warned residents earlier this month about the dangers of using neti pots improperly after a second death in the state in 2011.

A 51-year-old DeSoto Parish woman died after using tap water in a neti pot to irrigate her sinuses and became infected by the deadly amoeba, which entered the body through her nose. In June, a 20-year-old St. Bernard Parish man died under the same circumstances.

Health officials recommend irrigating or rinsing the nose using only distilled, sterile or boiled water. Neti pots or other irrigation devices should be rinsed after each use and allowed to dry.