‘Brain-Eating’ Amoebae hit the headlines – should we be afraid?

by Julia Diebol on August 23, 2011

An amoeba called Naegleria fowleri has been making news headlines recently (see, for example, CBS News, or U.S. News and World Report), where it is being referred to as the ‘brain-eating’ amoeba.  Three deaths have been confirmed in the U.S. this summer due to infections: two people in August from swimming in rivers or lakes and one person in June from using contaminated tap water in a neti-pot.  (The amoeba enters the body through the nose via contaminated water and travels to the brain, where it can destroy brain tissue.)

In terms of probability, the risk of infection is small – the CDC says infections are “very rare,” with 32 infections between 2001 and 2010 despite millions of exposures.  Also, the risk is not new, although it doesn’t seem to have made headlines in since 2008 according to a Google News search.

However, there are several factors that make the risk feel ‘scary’:

  1. The infection is almost always fatal, and the idea of something ‘eating’ a brain is particularly gruesome.
  2. The sources of exposure (lakes, rivers, and tap water) are common, making if feel as though everyday activities are putting people at risk.
  3. Those killed this summer have been young (all under 30 years old), making it feel as though everyone, even if otherwise healthy, is likely to be at risk.
  4. Amoebae [the plural of amoeba] are invisible to the naked eye.  You can’t tell if a body of water you’d like to swim in has zero or millions of amoebae in it just by looking at it.

When a risk feels scary, it can be challenging to communicate information clearly about the risk.  In this case, a few key messages (based on the CDC’s frequently-asked questions (FAQs)) could likely get lost in the transfer:

  1. There is no indication that the risk of infection is increasing.  An average of three deaths are reported each year in the U.S., mainly during the summer months, and mainly in southern states.
  2. The risk seems to be limited to warm, untreated, or poorly-treated water, with infections mainly resulting from swimming or diving in warm, shallow, freshwater lakes and rivers.
  3. Additional factors that may account for the extremely low number of infections compared to the number of people exposed to the same waters are unknown.
  4. The risk is limited only to exposure through the nose.  You cannot be infected with Naegleria fowleri by drinking or touching contaminated water.

For more information about Naegleria fowleri and other recreational water illnesses, see the CDC webpages on the topics.

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{ 4 comments… read them below or add one }

Mike August 23, 2011 at 3:24 pm

Would you be kind enough to call my mother to tell her she needn’t worry and that I don’t need to switch to distilled water for my neti-pot.

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Megan August 25, 2011 at 12:25 am

I’m kind of worried that I could have contracted an amoeba from using city water in my neti pot, which I used for the first time tonight. I live in Michigan – could it still happen here, and should I be worried?

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Daleth August 31, 2011 at 6:06 pm

Megan, of course it could happen. The point of the article is that it’s very unlikely, not that it couldn’t happen. An article that describes the neti pot death quotes the state epidemiologist saying “only sterile, distilled, or boiled water should be used in neti pots.”
That’s what you would need to do if you want to move from “very unlikely” to “can’t happen.”
http://www.mercurynews.com/science/ci_18707380

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Art September 3, 2011 at 4:27 pm

“The risk seems to be limited to warm, untreated, or poorly-treated water, with infections mainly resulting from swimming or diving in warm, shallow, freshwater lakes and rivers.”
Then this situation isn’t very limited considering that only people who strictly bath or swim in highly sanitized water are immune from infection. A lot of communities don’t sanitize water supplies very well and a lot of homes use wells which aren’t always deep or clean enough. If one doesn’t live in a big city one often is involved in some sort of water sports in some natural body of water. The list goes on and on to the point that the word “limited” just doesn’t isn’t appropriate.

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