a method for identifying a risk factor for diseases , disorders or conditions , such as those caused by human immunodeficiency virus , using the polymerase chain reaction and specific primers . methods for treating patients having these diseases , disorders or conditions by antimicrobial treatment of the risk factor by combined antiviral and antibacterial treatment or by sustaining or stimulating the subject &# 39 ; s immune system . methods for screening biological products including red blood cell preparations . primers and methods for detecting nucleic acids or microbial agents associated with red blood cells , such as those associated with red blood cells in subjects infected with hiv and undergoing antiretroviral therapy .