OPINION: Bad Ideas Are Spreading Like the Plague

From socialism to nationalism, debunked ideologies are making a return.

The defeat of measles in the United States was one of the great good news stories of the turn of the millennium. Prior to 1963, when a vaccine was developed, the highly contagious virus led each year to 48,000 hospitalizations and 400–500 deaths, mostly among small children, according to the Centers for Disease Control and Prevention (CDC). But immunization campaigns steadily eroded the disease's reach, and by 2000 it was declared eliminated from American shores.

Today, the U.S. is grappling...