Your skin protects you from HIV/AIDS as well as all kinds of other nasty stuff. HIV/AIDS is usually transmitted through sex or needle sharing. Very few people get it from just touching someone. For that to happen, the person you are touching has to be HIV positive (which is a minority population to begin with), then they have to have a cut or something for blood to get through, and you also have to have a cut or something for their blood to get through. If you do not have any cuts, then there is no way for anything to get through.

Be careful when working in the nursing home, wear gloves, and put a bandage on any cuts that you may have just in case, but it isn't really anything that you have to constantly worry about. People in nursing homes are having their health monitored, so if they had anything serious like HIV, the staff would probably be aware of it.