The deceased girl’s father insisted that measles helps build up a person’s immune system.

So here’s the thing…and I know that everyone here knows this, but it doesn’t.

Measles causes immune amnesia.

It’s pretty sneaky - integrating into respiratory tract macrophages, and avoiding destructive phagocytosis by binding directly to certain membrane receptors, and then being transported to lymph nodes where B and T cells get infected by the measles virus too. These memory B and T cells contain the memory of past infections, and when they’re destroyed (because they’re infected), you no longer have the ability to quickly ramp up a response to past infections and you get to start all over from the start.

So even if their other kids survived, their chances of dying from another infection goes up. It takes somewhere between 2.5 and 5 years for that risk to come back to baseline.

The infection itself might not have been “that bad” (despite killing one of their children) but the mortality risk isn’t over by a long shot.