Epidemiology TransmissionHIV has been isolated from semen, cervical secretions,lymphocytes, cell-free plasma, cerebrospinal fluid, tears,saliva, urine and breast milk. This does not mean, however,that these fluids all transmit infection, as the concentrationof virus in them varies considerably. Semen, blood, andpossibly cervical secretions are particularly infectious. Thecommonest mode of transmission of the virus throughoutthe world is by sexual intercourse: whether this is anal orvaginal is unimportant. Other methods of transmission arethrough the receipt of infected blood or blood productsand donated organs and semen. Transmission also occursthrough the sharing or reuse of contaminated needles byinjecting drug users or for therapeutic procedures, andfrom mother to child. Transmission from mother to childoccurs in utero, at birth (intrapartum) and through breastmilk.There is no well documented evidence that the virus isspread by saliva. It is not spread by casual or social contact.Health-care workers can, however, be infected throughneedle-stick injuries and by skin and mucosal exposure toinfected blood or body fluids. Finally, there is no evidencethat the virus is spread by mosquitoes, lice, bedbugs, inswimming pools, or by sharing cups, eating and cooking utensils, toilets or air space with an infected individual. Inother words, HIV and AIDS are not contagious.
