The kid who caught every cold​

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Catching a cold usually isn't a big deal, but one 5-year-old girl's her recurring colds end in hospitalization. The child, whose case was described Monday in the Journal of Experimental Medicine, has a rare mutation that stops parts of her immune system from functioning properly. By studying her case, scientists have a better idea of how our body fights off the cold and related viruses.

Why it matters: According to Su, the average adult gets 3-4 colds a year, and they usually recover with no problems. But sometimes they don't, and it is unclear why. "That's why it's really important to study cases like these. It's hard to tell when some viruses are dangerous and when some won't be."