The idea is that religions, like viruses, are costly to those infected
with them. They demand large amounts of money and time, impose health risks and make people believe things that are demonstrably false or contradictory. Like viruses, they contain instructions to "copy me", and they succeed by using threats, promises and nasty meme tricks that not only make people accept them but also want to pass them on.
This was all in my mind when Michael Blume got up to speak on "The reproductive advantage of religion". With graph after convincing graph he showed that all over the world and in many different ages, religious people have had far more children than nonreligious people.
All this suggests that religious memes are adaptive rather than viral from the point of view of human genes, but could they still be viral from our individual or societal point of view? Apparently not, given data suggesting that religious people are happier and possibly even healthier than secularists. And at the conference, Ryan McKay presented experimental data showing that religious people can be more generous, cheat less and co-operate more in games such as the prisoner's dilemma, and that priming with religious concepts and belief in a "supernatural watcher" increase the effects.