Measles are extremely contagious. So much so, they have a hitting average a major league batter would kill for. What makes measles so contagious is their ability to hide from our body’s immune system initial defenses. In fact, they hi-jack them to help it spread across the whole body.
When the measles virus enters our system, our white-blood cells are tricked into thinking the virus is not a threat. The measles virus then uses the white-blood cells as free transportation to the immune-system-central-station (lymph node).
Once in our lymphatic system all bets are off. The virus replicates and spreads throughout our entire body. Unfortunately the damage is not done yet. As it spreads, it also destroys cells (SLAM) in our body responsible for remembering how to deal with previous pathogens. Remember how you never get the same cold twice? That’s thanks to these cells in our body that remember how to fight and get rid off those previous cold viruses.
So not only are you sick from measles, but even after you recover, your body’s immune system is being reset. This means that after dealing with measles you are more susceptible to old viruses your body had already dealt with.
Measles do not actually kill you. It is that old virus that enters your weakened immune system that does.