Who's Zoomin' Who?

Plot:

A sexually transmitted disease breaks out and affects several members of the hospital staff. Meanwhile, Webber reluctantly tells Derek about his own medical concerns. Izzie and Cristina worry about a patient's wife and daughter who can't agree on his care. Burke treats his college buddy Bill, whose medical diagnosis raises some questions regarding his wife's actions. And just as Meredith and Derek grow more intimate, a surprise from his past shows up.