Well, first off, other characters who weren't on the Lastlook trip won't get infected until Day Two, the virus needs the day to grow to full strength. It would also be VERY hard to accidentally infect someone, as it's very much a purposeful act, and by the time the infection can be spread, the infected will want to spread the virus around.

Sedation IS possible, but by the time Carolina would be infecting people, she would have already got her powers. So it's possible, but it will be difficult.