Case: A 30-year-old Danish tourist (blond, athletic, good-looking) takes a tour of the Southwestern US on the "Green Turtle" (a school bus painted green and modified by hippies in the Haight to tour around the U.S.). The tourist took a swim in the hot springs in Arizona, but a few days later presented in the ER at UCSF with a headache, nausea, vomiting, and neck stiffness.
Was this a case of meningitis? The spinal tap revealed no bacteria. A few days later, the attractive Danish tourist died and his autopsy revealed the brain pictured above. The huge dark sections are portions where a deadly amoeba has penetrated his brain.
Naegleria fowleri is a free-living amoeba that lives in warm water. They are known to venture up a swimmer's nose, penetrate the cribiform plate, and reproduce in the brain, inevitably causing death within a few days. The mortality rate is 95% within one week.
I can't imagine being an infectious disease expert...how can you avoid becoming paranoid?