An otherwise healthy young boy was promptly rushed to a Southern California hospital last November after experiencing a headache, vomiting, fever, and an “altered mental state” that would eventually prove fatal.

Initially, doctors at the Intensive Care unit treated the boy for bacterial and viral meningitis. When he began showing signs of decreased consciousness and respiratory failure that would require intubation and assisted breathing, doctors conducted a CT scan that showed his brain was swelling. An analysis of his spinal fluid would confirm a grim diagnosis: a rare but often fatal amoeba called Naegleria fowleri – more commonly known as the brain-eating amoeba. 

He would be dead after just three days in the hospital.

Twelve days before his diagnosis, the boy had visited a natural hot spring in an area known as Hot Ditch in Southern California. It is here experts believe he contracted the free-living amoeba commonly found in warm freshwaters like hot springs, rivers, and lakes. N. fowleri enters the body through the nose where it travels to an olfactory nerve. The single-celled amoeba both breaks down brain tissue and can simultaneously trigger a fatal immune response, resulting in the death of 97 percent of its hosts in what is described as a “rare and devastating infection of the brain,” or primary amoebic meningoencephalitis (PAM).

Fewer than eight cases occur in the US annually with fewer than 40 cases being reported between 2006 and 2016, yet nearly every incident since 1962 has proven fatal. Most of the time the victim has been a young male exposed to warm recreational waters during the summer months. Last year, the brain of a 69-year-old woman in the US was turned to “mush” while a 29-year-old New Jersey man died from the infection after visiting a water park in Texas.

However, five survival cases in recent years lend hope for treating the infection. The administration of miltefosine, an investigational breast cancer and anti-leishmania drug, shows promise in killing free-living amebae, including N. fowleri, in the laboratory. In 2013, a 12-year-old girl diagnosed with PAM started a treatment of miltefosine in combination with therapeutic hypothermia and made a full neurological recovery. That same year, an 8-year-old boy also survived PAM after receiving miltefosine but suffered what is likely to be permanent brain damage. In his case, doctors did not cool his body to below its normal temperature. In the summer of 2016, a 16-year-old boy also contracted PAM and was treated using the same protocol as the 12-year-old girl. He also made a full recovery. In all three of the survivor cases, the patients were treated within just a few days of becoming ill.  

The California boy was also given miltefosine but it is not clear whether doctors induced therapeutic hypothermia. This is the ninth case in the State of California since 1971. The third occurring after the person was exposed to hot spring water.

Though contracting PAM after swimming is rare, the CDC notes that people should consider risks when swimming.