The last countries with polio have some important commonalities: They are rankled by terrorism that threatens health workers and makes it difficult to disseminate vaccines. But the root of this is often based in something else entirely: conspiracy theories that have grown out of stark mistrust in power.

This misinformation is a kind of virus in itself. Fighting dangerous conspiracy theories, as India has found, is its own important battle, as important and challenging as actually stamping out the poliovirus for good.

While the governments of Pakistan, Afghanistan, and Nigeria have committed to the distribution of polio vaccines, they can’t control the underground networks created by Al Qaeda, the Taliban, Boko Haram, and Islamic State, or ISIS.

Last April, militants killed seven Pakistani policemen who were guarding public health workers in Karachi. Later in 2016, the World Health Organization reported that two cases of polio had been found in Nigeria, in a part of the state isolated from the rest of the country by the terrorist group Boko Haram. In Afghanistan, militants blocked tens of thousands of children from being vaccinated.