Public-health officials are confronting dangerous ideas as much as a deadly disease.

The anatomy of a 1930 epidemic that wasn’t:

Was parrot fever really something to worry about? Reading the newspaper, it was hard to say. “not contagious in man,” the Times announced. “Highly contagious,” the Washington Post said. Who knew? Nobody had ever heard of it before. It lurked in American homes. It came from afar. It was invisible. It might kill you. It made a very good story. In the late hours of January 8th, editors at the Los Angeles Times decided to put it on the front page: “two women and man in Annapolis believed to have 'parrot fever.'"