In the fall of 2001 I was in Calcutta with the magnificent photographer Sebastião Salgado, a Brazilian genius whose studies with the camera have made vivid the lives of migrants, war victims, and those workers who toil to extract primary products from mines and quarries and forests. On this occasion, he was acting as an envoy of UNICEF and promoting his cause as a crusader — in the positive sense of that term — against the scourge of polio. Thanks to the work of inspired and enlightened scientists like Jonas Salk, it is now possible to immunize children against this ghastly malady for a negligible cost: the few cents or pennies that it takes to administer two drops of oral vaccine to the mouth of an infant. Advances in medicine had managed to put the fear of smallpox behind us, and it was confidently expected that another year would do the same for polio. Humanity itself had seemingly united on this proposition. In several countries, including El Salvador, warring combatants had proclaimed cease-fires in order to allow the inoculation teams to move freely. Extremely poor and backward countries had mustered the resources to get the good news to every village: no more children need be killed, or made useless and miserable, by this hideous disease. Back home in Washington, where that year many people were still fearfully staying indoors after the trauma of 9/11, my youngest daughter was going dauntlessly door to door on Halloween, piping «Trick or Treat for UNICEF» and healing or saving, with every fistful of small change, children she would never meet. One had that rare sense of participating in an entirely positive enterprise.

The people of Bengal, and particularly the women, were enthusiastic and inventive. I remember one committee meeting, where staunch Calcutta hostesses planned without embarrassment to team up with the city’s prostitutes to spread the word into the farthest corners of society. Bring your children, no questions asked, and let them swallow the two drops of fluid. Someone knew of an elephant a few miles out of town that might be hired to lead a publicity parade. Everything was going well: in one of the poorest cities and states of the world there was to be a new start. And then we began to hear of a rumor. In some outlying places, Muslim die-hards were spreading the story that the droplets were a plot. If you took this sinister Western medicine, you would be stricken by impotence and diarrhea (a forbidding and depressing combination).

This was a problem, because the drops have to be administered twice — the second time as a booster and confirmation of immunity — and because it takes only a few uninoculated people to allow the disease to survive and revive, and to spread back through contact and the water supply. As with smallpox, eradication must be utter and complete. I wondered as I left Calcutta if West Bengal would manage to meet the deadline and declare itself polio-free by the end of the next year. That would leave only pockets of Afghanistan and one or two other inaccessible regions, already devastated by religious fervor, before we could say that another ancient tyranny of illness had been decisively overthrown.

In 2005 I learned of one outcome. In northern Nigeria — a country that had previously checked in as provisionally polio-free — a group of Islamic religious figures issued a ruling, or fatwa, that declared the polio vaccine to be a conspiracy by the United States (and, amazingly, the United Nations) against the Muslim faith. The drops were designed, said these mullahs, to sterilize the true believers. Their intention and effect was genocidal. Nobody was to swallow them, or administer them to infants. Within months, polio was back, and not just in northern Nigeria. Nigerian travelers and pilgrims had already taken it as far as Mecca, and spread it back to several other polio-free countries, including three African ones and also faraway Yemen. The entire boulder would have to be rolled back right up to the top of the mountain.

You may say that this is an «isolated» case, which would be a grimly apt way of putting it. But you would be mistaken. Would you care to see my video of the advice given by Cardinal Alfonso Lopez de Trujillo, the vatican’s president of the Pontifical Council for the Family, carefully warning his audience that all condoms are secretly made with many microscopic holes, through which the AIDS virus can pass? Close your eyes and try to picture what you might say if you had the authority to inflict the greatest possible suffering in the least number of words. Consider the damage that such a dogma has caused: presumably those holes permit the passage of other things too, which rather destroys the point of a condom in the first place. To make such a statement in Rome is wicked enough. But translate the message into the language of poor and stricken countries and see what happens. During carnival season in Brazil, the auxiliary bishop of Rio de Janeiro, Rafael Llano Cifuentes, told his congregation in a sermon that «the church is against condom use. Sexual relations between a man and a woman have to be natural. I have never seen a little dog using a condom during sexual intercourse with another dog». Senior clerical figures in several other countries — Cardinal Obando y Bravo of Nicaragua, the archbishop of Nairobi in Kenya, Cardinal Emmanuel Wamala of Uganda — have all told their flocks that condoms transmit AIDS. Cardinal Wamala, indeed, has opined that women who die of AIDS rather than employ latex protection should be considered as martyrs (though presumably this martyrdom must take place within the confines of marriage).

The Islamic authorities have been no better and sometimes worse. In 1995, the Council of Ulemas in Indonesia urged that condoms only be made available to married couples, and on prescription. In Iran, a worker found to be HIV-positive can lose his job, and doctors and hospitals have the right to refuse treatment to AIDS patients. An official of Pakistan’s AIDS Control Program told Foreign Policy magazine in 2005 that the problem was smaller in his country because of «better social and Islamic values». This, in a state where the law allows a woman to be sentenced to be gang-raped in order to expiate the «shame» of a crime committed by her brother. This is the old religious combination of repression and denial: a plague like AIDS is assumed to be unmentionable because the teachings of the Koran are enough in themselves to inhibit premarital intercourse, drug use, adultery, and prostitution. Even a very brief visit to, say, Iran, will demonstrate the opposite. It is the mullahs themselves who profit from hypocrisy by licensing «temporary marriages», in which wedding certificates are available for a few hours, sometimes in specially designated houses, with a divorce declaration ready to hand at the conclusion of business. You could almost call it prostitution… The last time I was offered such a bargain it was just outside the ugly shrine to the Ayatollah Khomeini in south Tehran. But veiled and burqa-clad women, infected by their husbands with the virus, are expected to die in silence. It is a certainty that millions of other harmless and decent people will die, very miserably and quite needlessly, all over the world as a result of this obscurantism.

The attitude of religion to medicine, like the attitude of religion to science, is always necessarily problematic and very often necessarily hostile. A modern believer can say and even believe that his faith is quite compatible with science and medicine, but the awkward fact will always be that both things have a tendency to break religion’s monopoly, and have often been fiercely resisted for that reason. What happens to the faith healer and the shaman when any poor citizen can see the full effect of drugs and surgeries, administered without ceremonies or mystifications? Roughly the same thing as happens to the rainmaker when the climatologist turns up, or to the diviner from the heavens when schoolteachers get hold of elementary telescopes. Plagues of antiquity were held to be punishment from the gods, which did much to strengthen the hold of the priesthood and much to encourage the burning of infidels and heretics who were thought — in an alternative explanation — to be spreading disease by witchcraft or else poisoning the wells.