The St. Bernard Parish water system in Louisiana has tested positive for the rare brain-eating amoeba that killed a 4-year-old boy last month, the U.S. Centers for Disease Control confirmed Thursday.

Health officials said the water is drinkable but becomes dangerous when ingested through the nose. The amoeba is present in four locations in the St. Bernard Parish water system and officials are urging residents to take precautionary measures to prevent infection.

"While the water is safe to drink, there is a risk if the amoeba enters the nose," State Health Officer Jimmy Guidry told the Times-Picayune. "There are basic precautions that families can take -- such as chlorinating their pools and avoiding getting water in their noses -- to protect themselves, though infection from this amoeba is very rare."

Officials believe the parish water system became compromised after its chlorine levels were low, according to state Assistant Health Secretary J.T. Lane. The parish will be flushing its water lines with chlorine for several weeks until they reach recommended levels, CNN reports.

Naegleria fowleri
The deadly brain-eating amoeba or Naegleria fowleri has been found in the St. Bernard Parish water supply in Louisiana, the U.S. Center for Disease Control confirmed Thursday. CDC

Three children contracted the parasite this summer. A 4-year-old Mississippi boy playing on a water slide in St. Bernard Parish contracted amoebic meningoencephalitis and died last month. The same parasite killed 12-year-old Zachary Reyna in Florida last month. And Arkansas preteen Kali Hardig, 12, survived the infection she contracted in July.

The brain-eating amoeba Naegleria fowleri is commonly found in warm fresh water and enters the body through the nose, where it travels to the brain and is usually fatal, according to the CDC.

Initial symptoms begin one to seven days after infection and can include headache, fever, nausea, vomiting and stiff neck. Later, symptoms include confusion, attention problems, loss of balance, seizures and hallucinations. The disease progresses rapidly and usually causes death within 12 days.

Below are the do's and don’ts for preventing infection:

Do:

Run bath and shower taps and hoses for five minutes before use to flush out the pipes. This is most important the first time you use the tap after the water utility raises the disinfectant level.

Keep small hard-plastic/blow-up pools clean by emptying, scrubbing and allowing them to dry after each use.

Use only boiled and cooled, distilled or sterile water for making sinus rinse solutions for neti pots or performing ritual ablutions.

Place the hose directly into the skimmer box and ensure that the filter is running.

Keep your swimming pool adequately disinfected before and during use. Adequate disinfection means:

Pools: free chlorine at 1-3 parts per million (ppm) and pH 7.2-7.8; hot tubs/spas: free chlorine 2-4 parts per million (ppm) or free bromine 4-6 ppm and pH 7.2-7.8. If you need to, top off the water in your swimming pool with tap water.

Don’t:

Don't allow water to go up your nose or sniff water into your nose when bathing, showering, washing your face, or swimming in small hard-plastic/blow-up pools.

Don't jump into or put your head under bathing water (bathtubs, small hard-plastic/blow-up pools).

Don't allow children to play unsupervised with hoses or sprinklers, as they may accidentally squirt water up their nose. (Avoid slip-n-slides or other activities where it is difficult to prevent water going up the nose.)

Don't top off by placing the hose in the body of the pool.