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’:
- The infection is almost always fatal, and the idea of something ‘eating’ a brain is particularly gruesome.
- The sources of exposure (lakes, rivers, and tap water) are common, making if feel as though everyday activities are putting people at risk.
- 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.
- 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:
- 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.
- 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.
- 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.
- The risk is limited only to exposure through the nose. You cannot be infected with Naegleria fowleri by drinking or touching contaminated water.
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