1)well to host it as in activate the infection yourself from a 1.13 patch u have to have 2 ps3's 1 on the latest update and 1 on 3.55 or a lower Jailbreakable firmware. You put the 1.13 patch on your 3.55 then u Data Transfer to Your Online Ps3
2)The Other way idk if u mean this way but if u get into a uav lobby and u back out and go into a private match you will still have the infected map from there u can just keep hosting it for your friends or u can go do the infection

but once you turn off your ps3 or go to the main menu the infection goes away.
i hope this helped you understand a little better how to host it.