I recently finished Darrel Ray's The God Virus, which builds off of Richard Dawkins' concept of a meme and, Ray purports, the work of Daniel Dennet (though I have not yet had the pleasure of reading Dennet's work, so I cannot speak to this, but we'll give him the benefit of the doubt ;) ).
The book itself was interesting, presenting the idea of religion as a virus: it infects the mind, uses the mind's immunity mechanisms to protect itself against competing religious ideas. I was disappointed, though, that Ray didn't address what I thought was a very fair concession: the concept of an idea as a virus is not restricted to religion. While one could argue that the book was very focused on the religious idea virus, I think that, in all fairness, a proper reflection on the idea contrary to religion - atheism - as a virus would have made for a more informative read. As such, I'll put my thoughts on atheism as a virus.
First, to give a brief overview of the concept of "idea as a virus": Ray discusses how an idea will invade the mind and establish defenses within the infected individual to prevent other ideas from kicking it out. This also helps to facilitate the idea of "natural selection" of ideas - those ideas that are incapable of protecting their claim on individuals will eventually wither and die. Darrel Ray, in his book, gives several examples of the various religious viruses achieving this.
Atheism has its roots firmly set in the skepticism movement - the "show me" movement, for which Missouri, my home state, claims as its nickname. As such, it shares the same defenses as skepticism: critical thinking, demands of evidence and/or rational basis, and likely others that I have not yet discovered through introspection. By teaching those infected with the "skepticism" virus to apply these practices, the vector of the virus - the advocate of skepticism - ensures that competing ideas, such as religion, UFO abductions, demonic possessions, ghost hauntings, racism, sexism, and anti-LGBT sentiments, will find sufficient resistance to either fail to get a foothold or fail to even get in through the front door. The success of the defenses comes in varying flavors - too weak (atheists who lapse back into religion), too strong (gnostic atheists), and various strengths in between. At the risk of stating the obvious, I believe agnostic atheism to be the most-balanced position.
Now, then, we're left with atheism and theism both meeting the criteria as viruses, with each configuring its infected individuals with practices to defend against infection by the competing idea. What, then, makes one better than the other?
I'll preface the next part of this post by saying that, when I refer to religion, I refer to ones that actively seek to convert - Christianity and Islam being the most relevant examples to the western world. There are plenty of harmless, non-evangelistic religions such as Wicca, pagan religions, Satanism, and other "minor players" that, although I disagree with them on the grounds of rationality, aren't to be worried about since they don't have any concerns with propagation or retention of believers.
Popular religions tend to punish people for leaving their religion. Beyond just the "guilt cycle" that Darrel describes in his book, the popular religions threaten those who consider leaving with death. In Christianity and Judaism, Moses and Aaron murder three thousand people for leaving the Jewish religion and worshiping a golden calf (thankfully, the modern-day manifestations of these religions do not tend to advocate something so severe); in Islam, the punishment can be death for leaving the religion, weaving itself into the laws of nations like Afghanistan. Less-severe instances of punishment for apostasy can constitute things such as eviction by parents of their children from their home, such as was the case for Damon Fowler.
Atheism, however, prescribes no such punishment for relapsing into irrationality; in the rare event that someone is threatened with any punishment for merely not being an atheist anymore, anyone who describes themselves as secular humanist should denounce such an act, if not offer means to support the affected individual, much like they do for atheists facing the same backslash from theists.
Beyond consequences of apostasy is the fact that theism opens the door to let irrationality in; very often, the logical fallacies and inconsistencies of religion are ignored under the guise of "having faith", and that this purposeful ignorance of flaws in one's beliefs is even considered a virtue in many religious circles. Skeptics, on the other hand, define their beliefs based on what can be rationally concluded (officially, anyway, and it's the job of a skeptics' skeptic friends to point out when they haven't). This can be embodied no better in the following questions: when was the last time an atheist had a demon exorcised from them? What special power does atheism bestow upon an individual that protects them from Satan's minions' influence? And before anyone dismisses exorcism as having gone out of style with the movie "The Exorcist", I'll remind you that the Catholic church still has exorcists who occasionally get themselves into the news.
In the end, skepticism - and atheism - is a virus, just like theism. The difference - the very, very important difference - is that the mechanisms that skepticism uses to protect itself from being displaced don't typically call for anyone's death or lesser forms of punishment, but instead provoke a breakdown and analysis of the opposing idea, leaving the individual open still to consideration of opposing viewpoints. The omission of this doesn't subvert Darrel's writing - it's still very much a worthwhile book - but I think it would have definitely benefited from such an introspective analysis. Beyond that, I can only imagine how much better this would have sounded if it was written by someone with a degree in sociology rather than information technology.