My sister just found out that the father of her children (with whom she separated 3 yrs ago) tested positive for HIV 6 days ago.

She was tested for "everything" just after they broke up in '05.

About two months ago they did have sex (drunken retardedness that unforutnately happened) and she has also treated a bleeding cut on his finger.

Time line of events:
* Has been living in FL for 3 yrs where GOD knows what he's been doing.
* He was tested in April '08 and it came back negative.
* Moved back from FL in July '08
* Drunken sex night (with my sister) occured sometime in Sept
* He had another random encounter with a girl at a party over Halloween.
* He tested positive within the last week. (today is 12/3/2008)

My questions are...
* Is is possible that he contracted this virus from the Halloween night girl or has it shown up too quickly?
* Is there a chance the virus was not transmitted if he was infected before the Halloween evening?
* Is there anything that she can do to prevent establishment of the virus at this point?
i.e. immune boosting drugs/supplements or anything of that nature?

Any credible info on this would be greatly appreciated.

Thank you.