Troubadour, 24 hours ago I posted this,

"Anal sex is far more risky than vaginal, but as Musket says, heteros do it too.
Unprotected sex is far more risky.
That is an issue for all preferences.
Multiple, concurrent partners is far more risky.
That is an issue for all preferences.
Does anyone know a different issue, or are these the issues that determine infection rate in any preference group?"

No-one came back with any other issue.
Those ARE the issues that determine infection rate in sexual transmission.