Watts-MacLeod is the only strain of exsurgent virus which doesn’t result in death (of the infected and generally everyone around them) in short order. If someone is believed to have a latent infection of any kind, it’s very likely that habitat authorities will be looking to quarantine them – if an angry mob doesn’t incinerate their morph first. Therefore, public knowledge of the Watts-MacLeod virus is effectively nil. Further, many of the infected don’t even know that they’ve caught it and merely think that they’re going mad. Which isn’t to say that there’s no truth to the theory.
If you choose to play an async, be aware that the virus is the touch of the incomprehensibly alien and Other on your character. The only thing about it that you can be certain of is that it persists as though a part of you, and you will never be free of it. You need to take an aspect related to Watts-MacLeod/asyncs/PSI in order to access any of their abilities. (It makes a great Trouble.) Due to the strain of reconciling between the Earth-derived and incompletely integrated alien aspects of their brains, asyncs also start the game with one moderate mental consequence (nature TBD by player & GM) which can be treated as usual with psychological assistance.
The abilities that an async has learned to use coherently and more-or-less at will are known as sleights. So far as crunch goes, these are Will stunts that either enhance a character’s mind (Ψ-χ) or influence other minds housed in biological brains (Ψ-γ). The list of sleights in the EP sourcebooks are a good place to start, but by no means the be-all end-all of async abilities.