In Who's Afraid of Virginia Woolf? sex and infidelity are mostly used as weapons. The characters commit sexual acts or threaten them as way of gaining power over each other. In a few instances, characters try to become intimate in order to connect with each other. These attempts at true intimacy are short lived, however. For the most part, like most everything else in the play, sex is a tool for battle.
In Who's Afraid of Virginia Woolf? sex is more often linked with power than intimacy.
Martha's almost infidelity is the last straw for George; it's what causes him to "kill" their imaginary son.