Many, perhaps millions, have died from mumps, and the rest of us are descended from the survivors, inheriting their immune responses. This is why almost no one dies from the mumps anymore.

Native Americans were ravaged by many plagues that eliminated perhaps 98% of them between 1492 and LaSalle's expedition up the Mississipi River roughly a century later, including the mumps.

It is unknown how many the mumps, or any other disease communicated by Colombus's crew, killed directly, but it is known that mumps did cause deaths in Native Americans, who had no resistance at all to the new, to them, disease.