That number was a surprise on the low side for me, because I've often heard estimates that 25%-30% of adults in the US have HSV-2. Naively scaling that up to worldwide would have suggested up to 2 billion infections.
For example, Australia's rate of HSV-2 is around 12% while the UK is around 10% even though we have fairly similar cultural backgrounds when it comes to sexual activity.
I would expect that rate to be much lower in some middle eastern and asian cultures due to differences in culture regarding sexual activity.
536 million might be on the conservative side, but I would suggest it's nowhere near 2 billion.
And it just so happens one of the primary ways women catch HSV-2 is through a partner infecting them orally. There are "virgins" getting herpes in America.
Now, again, culturally, I've been told that Aussie men are incredibly chauvinistic, so maybe a smaller percentage is likely to engage in oral sex. I'm generalizing and speculating here , so take it with a grain of salt. In the UK, the sex education could be better. From talks with my friends from southern states, it seems you'd have to deliberately try to do worse.
Furthermore, there was at least some issue in that many doctors were more conservative, and didn't really like talking about oral sex. (I heard this from a doctor who was complaining about this).