Strong new evidence suggests a virus triggers multiple sclerosis

If you were to ask any of the 1 million Americans living with multiple sclerosis, they’d probably say their disease started with changes so small they almost didn’t notice them: a wobbly step, a weakening grip, sight going soft around the edges. But MRI scans of their brains — dotted with ghostly white scars — would tell a different story.

Those scars are signs of inflammation dating back multiple years. Each spot represents a dead zone filled with mangled remains of thousands, sometimes millions, of neurons. Like city blocks going dark during a power outage, these cells blinked out one by one after an immune storm stripped off the insulating myelin sheath that helps them send and receive electrical signals. But what triggers the immune system to turn on itself is still a mystery.

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