Might have been a flat answer, but a correct one.

Just googleing “measles auto immune” gives you ample links that go in depth on why and how measles infections can CAUSE autoimmune conditions, like e.g. this one: my.klarity.health/measles-and-its-role-in-trigger…

And one mechanism how they do that is specifically by confusing the immune system into not knowing what’s friend or foe, so that it starts attacking the body instead of contageons.