A Texas city is grappling with a brain-eating amoeba in its water like something out of a Hollywood movie.

Eight Texas cities have warned residents about using their tap water after the deadly brain-eating amoeba was found in the public water supply. A Do Not Use Water Advisory was issued for residents of Lake Jackson, Freeport, Angleton, Brazoria, Richwood, Oyster Creek, Clute, and Rosenberg, Texas, as well as for the Dow Chemical plant in Freeport and the Clemens and Wayne Scott Texas Department of Criminal Justice corrections facilities.

Tests of Lake Jackson’s water supply confirmed the presence of Naegleria fowleri an amoeba that can cause an infection of the brain, which is ordinarily fatal. Lake Jackson City Manager Modesto Mundo said, three of 11 sample tests indicated preliminary positive results for the brain-eating microbe, with one sample coming from the boy’s home.

Naegleria fowleri is a free-living amoeba that causes primary amebic meningoencephalitis (PAM), a disease of the central nervous system.

Naegleria fowleri infections are extremely rare in the U.S. but the contagion is almost always fatal. In the United States, there have only been 145 PAM infections from 1962 through 2018 with only four survivors according to the CDC. If humans accidentally drink the microbe, it’s harmless. But if it makes its way inside the nose it’s usually lethal.

Officials in Lake Jackson stated they were disinfecting the water supply. However, they said they did not know how long the process would take.

The Eight Texas communities were originally told on Friday night not to use their water supply for any reason except to flush toilets. The warning was lifted on Saturday by the Texas Commission on Environmental Quality (TCEQ)for everywhere but Lake Jackson, a city of more than 27,000 residents, The BBC reported.

Authorities in Lake Jackson later said that people could begin using the water, but must boil it before drinking it. Residents were also told to take other measures, including not allowing water to go up their noses while showering or bathing. According to TECQ, the boil-water notice will remain in place until the authority’s water system has been thoroughly flushed and tested to show clear water samples indicating the system’s water is safe to use again. The authority said in a statement that it was unclear how long it would be before the tap water was again safe.

The city further warned that children, elderly people, and people with weakened immune systems were “particularly vulnerable” to Naegleria fowleri.

Officials said they were beginning to decontaminate and flush the water system, and would later run more tests to ensure the water was safe to use.

An investigation into the city’s water supply began after a six-year-old boy Josiah McIntyre contracted the microbe and died earlier this month, Lake Jackson City Manager Modesto Mundo told reporters.

Naegleria fowleri occurs naturally in freshwater, the soil, warm lakes, rivers, and hot springs. It usually infects people when contaminated water enters the body through the nose and then travels to the brain.

The Centers for Disease Control and Prevention (CDC) says infection typically happens when somebody go swimming or diving in “warm freshwater places”.

The CDC says people cannot get infected by swallowing contaminated water, and it cannot be passed from person to person.

Those infected with Naegleria fowleri have flu-like symptoms including fever, nausea, and vomiting. Besides the normal symptoms showing someone is sick Naegleria fowleri comes with a stiff neck and headaches. Most people infected do not recover and usually die within just a week after the amoeba is within their brain.

Earlier this year an infection of Naegleria fowleri was confirmed in the U.S. state of Florida. At the time, health officials there urged locals to avoid nasal contact with water from taps and other sources. Two children in Minnesota died from N. fowleri in 2010 and 2012 — both cases “550 miles north of the previously reported northernmost case in the Americas.”

The amoeba was found to be thriving in U.S. rivers and lakes more and more, earlier this year. Insider reports that cases may increase as climate change warms waters. Experts estimate that between 3 and 8 Americans die from N. fowleri annually.