HIV and ID Observations

Sometimes it takes a lot to surprise an ID doctor — we who try to make it seem like we’ve seen it all — but certain infections are either so severe (e.g., necrotizing fasciitis from group A strep) or so rare (e.g., endocarditis from Erysipelothrix rhusiopathiae) that even we are startled.

Doubly startling are those infections that score 10 out of 10 on both the severity and the rarity scale.

No doubt one such condition is primary amebic meningoencephalitis (PAM), the brain infection that tragically just led to the death of a 12-year-old boy in Florida.

The pathogenesis of PAM is straightforward:

1. Naegleria fowleri live in warm freshwater lakes and ponds.
   
2. The parasite enters the body through the nose, usually when someone swims or dives in these waters. (Some cases occur when contaminated water is used for nasal irrigation).
3. From the nose, the Naegleria travel back into the brain, causing a severe necrotizing infection that is almost invariably fatal.

However, just because we know how it happens, by no means we know why on an individual level.

Said another way, given the millions of people who swim in warm lakes and ponds each year, why have there been only 31 cases from 2003-2012? Why did this poor boy get sick, but his friends did not?

A case like this is a reminder that, no matter how experienced the clinician, the world of infections and how they cause human disease remains a humbling life’s work.