Immunity Amnesia

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Like many viruses, measles is known to suppress the immune system for a few weeks after an infection. But previous studies in monkeys have suggested that measles takes this suppression to a whole new level: It erases immune protection to other diseases, Mina says.

So what does that mean? Well, say you get the chicken pox when you're 4 years old. Your immune system figures out how to fight it. So you don't get it again. But if you get measles when you're 5 years old, it could wipe out the memory of how to beat back the chicken pox. It's like the immune system has amnesia, Mina says.

"The immune system kind of comes back. The only problem is that it has forgotten what it once knew," he says.