If you thought Billy Bush was infectious as the host of the Miss USA pageant, there's a reason -- he had mono. Bush dropped the info on his Twitter page yesterday -- "Health has been off the last 2 wks. Tests are back. I have mono." Billy planted a kiss on Miss Universe's face during the show. Miss U then kissed his co-host Nadine Velazquez ... who then kissed Miss West Virgina. TMZ spoke to a rep for Miss Universe just a few minutes ago, who told us Miss U "feels fine ... no mono-like symptoms." We're trying to get...