My English is not good, I tried to describe my problem. I had sex with my girlfriend in a hotel room last night (opening the room at about 9:30 pm, and making love at about 11:30 pm). We got up this morning and suddenly found blood on the bed, but we can't be sure if the blood is our own. During the process of making love, our body were very likely to come into contact with the blood on the sheets（But we can't confirm if the bloodstain was dry at the time）. I would like to ask if the blood is left by the people who lived in this hotel before, and the hotel did not change the sheets（It is possible in our country）, are we at risk of having AIDS if the people lived in this room before have AIDS?