... infections, and the viruses that causethem perish within a few hours outside the humanbody.Health experts distinguish between colds and u on the basis of the viruses that cause them and the distinctions ... contact, such asthrough kissing, also spreads the virus. Though the strain of herpes simplex virus that causes coldsores, HSV-1, is different from the strain HSV-2,which causes GENITAL HERPES, ... family of viruses, the human rhino-viruses (HRVs), cause colds. Five strains of HRVcause 90 percent of colds. With most viruses,including those that cause the u, the body devel-ops immunity...