If Ebola ever infects a promiscuous homosexual man in the US, it will spread through the whole gay community within a month.
For that matter, if Ebola ever infects a promiscuous man (or woman) in the US, it will spread through the community within a month.
But, the thing to note is that far more casual contact than sexual relations will spread the disease. You don't even need to get kissed (although all that will do the job).