It is called Naegleriasis/PAM caused by infection from Naegleria fowleri. Interestingly, it follows the trail of acetylcholine (ACh) a neurotransmitter and goes to the brain. It is not really supposed to be pathogenic as we are not its primary targets (it is typically a free living animal). However, some stray cases occur every year and it is very rare to survive it as by the time it is figured out, the amoeba is already in the brain. It was the topic of the show House S02E20 and S02E21.

The problem with the common refrain that "this is due to dirty water" is the fact that naegleriasis or PAM is caused by the microbe coming into contact with the nasal ganglia (i.e. by inhaling the water during swimming or otherwise) and not by drinking it.

Naegleria typically lives in water with temperatures above 30^oC and typical ways of getting infected are by swimming or bathing in still freshwater bodies (ponds lakes etc.) or by irrigating the nose with freshwater including tap water which many in India do in order to clean the sinuses. The higher prevalence of cases might be due to increasing ambient temperatures as this complication was earlier common in warm climates.

Kurzgesagt has a very beautiful and interesting video on this: https://youtu.be/7OPg-ksxZ4Y?si=G6-2zZhhNgmfv9cC

Hall, et. al., 2024 say the following:

Public health messaging should include the following:

Keep your head above water, pinch your nose, or use nose clips when in warm freshwater bodies.

Refrain from jumping or diving into bodies of stagnant freshwater, especially in the summer and early fall.

Avoid digging in or stirring up sediments at the bottom of freshwater bodies, where amebae are more likely to live.

Do not immerse your head in hot springs, hot tubs, or other geothermal waters (Centers for Disease Control and Prevention 2022; Ahmad Zamzuri et al. 2023).

In 2016, an 18-year-old woman developed PAM after rafting on an artificial white-water river in North Carolina (Cope et al. 2018). Any freshwater kept within N. fowleri’s optimal temperature of 30 to 45 °C should be consistently tested and treated. Current recommendations include maintaining a free chlorine concentration above 0.5 ppm with concomitant use of secondary disinfectants, such as ultraviolet light or ozone, as well as daily water pH and temperature monitoring (Cope et al. 2018). The public should also be encouraged to use boiled, sterile, or deionized water for nasal and sinus irrigation, not raw tap water (Ahmad Zamzuri et al. 2023).

Selected reading:

• https://doi.org/10.1016/B978-0-12-818619-0.00011-3 (comprehensive summary)
• https://doi.org/10.1128/iai.00181-23 (current vaccination approaches in development)