Misinformation about politics may often seem silly — the immigration bill will give out free cars! — but the consequences of false beliefs in public health can be deadly.

In the developed world, myths about the risks of vaccines have enabled the resurgence of communicable diseases like measles and pertussis. And in developing countries, false beliefs have hindered efforts to fight H.I.V./AIDS and eradicate polio in countries like Nigeria and Pakistan.

The latest example of the dangers of health misinformation comes from Western Africa, where the response to an Ebola outbreak in four countries has been hampered by conspiracy theories about its causes and phony rumors about how to treat it. False beliefs may not be the biggest obstacle to containing the Ebola outbreak, but they make an awful situation worse.

People in the affected regions have become especially distrustful of doctors, with some suggesting the disease is a hoax. A resident of a heavily affected area in Liberia told The Wall Street Journal last week: "I've never seen anybody die of Ebola. I've only heard of it. So it's a rumor." These beliefs are often based on conspiracy theories that the disease was invented by national governments in search of international aid or political power.