"Myth" 1: HIV Spreads Like Wildfire

It does not, Shelton argues, noting that only 8% of people whose heterosexual partner carries HIV become infected each year.

"This low infectiousness in heterosexual relationships partly explains why HIV has spared most of the world's populations," Shelton writes.

That may be true, Dickinson counters. But when a person is first infected with HIV -- and still is negative on most HIV tests -- that person is extremely infectious. This means that in certain circumstances HIV can spread fast.

"Let's say you are a young adult and single and living on South Beach and you go clubbing every weekend and are somewhat promiscuous," Dickinson tells WebMD. "If you have an acute HIV infection, it will spread like wildfire. This is not a conflagration that will cover a whole continent. But in individual places, HIV spreads rapidly."