Maybe I'm being anal about this, but isn't saying "By having sex with one person, you're having sex with x persons", or even just saying "having sexual contacts with x persons", like, way way WAY overexagerating?
I mean yeah, if we're talking STDs..
IF you have unprotected sex
IF your partner has had unprotected sex before
IF it was with a diseased partner
IF your partner contracted the disease
etc.
Other than that, no I'm not marveling about the numerous people I'm supposedly "having sexual contacts" with in just one night.
It would be akin to giving a handshake to someone and marveling "Woooaah, with only this handshake, I'm having indirect hand contact with thousands and thousands of people through a HAND SHAKING NETWORK!"
... Anyway, yeah.. STDs are bad.. use protection