Brain-eating ameba rare, but deadly
August 17, 2015
While the public health officer for Alpine, Mono and Inyo counties doesn't take lightly the death of a young Bishop, Calif., woman earlier this summer from primary amebic meningoencephalitis, Dr. Richard O. Johnson emphasizes that it was an extremely rare case.
After she was diagnosed with meningitis and admitted for treatment at Northern Inyo Hospital in June, the unidentified 21-year-old Bishop woman was transported to Renown Regional Medical Center, where she went into cardiac arrest and died. Testing done by the Centers for Disease Control and Prevention in Atlanta turned up positive for Naegleria fowleri, Dr. Johnson noted in a report.
The death is one of three reported in the U.S. this summer from a brain-eating ameba that lives naturally in warm freshwater sources as lakes, rivers, ponds, ditch water and hot springs, the CDC website reports.
While issuing a heads-up for the public, Johnson stressed that the infection is a rare occurrence.
"The emphasis is that anyone who has contact with untreated fresh water is at very low risk, anywhere, anytime," he said this week. "This is an incredibly low risk, as there are so few cases each year, in spite of millions of contacts with fresh water. To put it in perspective, at least 17 persons have been killed by lightning this year."
Johnson explained that a person can become infected when water containing the micro-organism enters the nose, usually while swimming or diving. People do not get infected by drinking contaminated water and the ameba has never been shown to spread from one person to another.
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"I want to emphasize there have been no evident cases of ameba contamination in the U.S. in well-maintained, properly treated swimming pools or hot springs," Johnson noted. "Appropriate regular filtration and chlorination or other types of disinfectant should eliminate the risk."
He added that officials believe the exposure in Inyo County occurred on private property used by family and friends and does not represent any risk to the general public.
"We did a site visit a few weeks ago and water was obtained for testing by the CDC, but results are not back yet," he said, noting that the suspect site is currently fenced and gated with no full-time residents.
Dr. Evan Easley, Carson Valley Medical Center chief medical officer, said he is not aware of any cases in Douglas County or Northern Nevada.
"To my knowledge we have not, and I've been here 20 years," Dr. Easley said this week. "To my understanding, it's found typically in warm water, though it can survive in some colder water. It tends to get down into the sediment and if the sediment gets disturbed it can get more dispersed in the water."
From 2005 to 2014, 35 infections were reported nationwide, according to the CDC website. Of those cases, 31 people were infected by contaminated recreational water, three as a result of nasal irrigation using contaminated tap water and one person was infected by contaminated tap water used on a backyard slip-n-slide.
CNN reported that an Oklahoma man died on Wednesday after swimming last week in Lake Murray in Ardmore, Okla.
While the infection is a greater risk in southern states, three cases have been confirmed in Minnesota since 2010. A 14-year boy died after swimming in a lake earlier this summer.
"It is an extremely rare situation where everything kind of had to be perfect, or imperfect, depending on your perspective, for this infection to actually occur," Easley said.
Johnson reported that uncommon and unusual sources include geothermal water, such as hot springs-tubs, canals, slip-n-slide, geothermal drinking water systems, swimming pools that are poorly maintained or minimally chlorinated and water heaters with temperatures less than 116 degrees Fahrenheit.
"The untreated hot springs and hang outs in the desert are always possible sources," he explained. "But commercial places should not be considered risky, as their water is treated and closely monitored.
"The mantra … Keep your head above water," he added.