Historically, cases of infection caused by the ‘brain-eating’ Amoeba (Naegleria fowleri) have been reported in the southern United States. However, in recent years, more and more cases have taken place towards the north of the country.
In a new study, a group of researchers from the U.S. Center for Disease Control and Prevention (CDC) examined cases of N. Fowleri infection in the country over a period of four decades (1978 to 2018). They were found to have shifted north, with more cases in the Midwestern states than before.
N. Fowleri is a single-celled organism that occurs naturally in the warm freshwater of lakes and rivers. The bacteria cause a devastating brain infection known as Primary Amoebic meningoencephalitis or – PAM – an almost always fatal disease.
Infections occur when water contaminated by this amoeba rises through person’s nose, allowing N. fowleri to enter the brain through olfactory nerves and destroy brain tissue. Drinking contaminated water, however, does not result in infection, Live Science explained, citing the CDC.
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Because this bacterium thrives in warm waters up to 45 degrees Celsius, it is possible that an increase in global temperatures could affect the geographic expansion of these organisms, the authors of the research consider.
During the period analyzed, the number of cases reported annually was fairly constant, varying from zero to six per year. The vast majority of the 74 records occurred in southern US states. Six of them, however, were reported in the Midwest, including the states of Minnesota, Kansas and Indiana. Five of these cases occurred after 2010, according to the report.
By analyzing weather data around the date each case occurred, the scientists found that, on average, daily temperatures in the two weeks prior to each case were higher than the historical average for each location.
“It is possible that rising temperatures and consequent increases in recreational water use, such as swimming and water sports, may contribute to the changing epidemiology of the PAM,” scientists said.
The study authors point out that knowing when and where these cases occur, and being aware of changes in their geographic range, could help predict the times when it is riskier to swim in lakes and rivers.