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I’ve been blogging a lot recently about dangerous viruses, like the flu and norovirus. But, truth be told, a lot of viruses we harbor don’t make us sick. They may even make us healthy. You’d think they’d be worth getting to know. But they’re mostly a mystery to us.

The collection of viruses that are dwelling inside you right now is known collectively as the virome. You might think these viruses were the sort that infect your cells. Some indeed are.