TRNSMISSION OF HIV

HIV is transmitted by three primary routes: sexual, parenteral (blood-borne), and perinatal. Virtually all cases of HIV transmission can be attributed to these exposure categories. Transmission rates from the infected host to the uninfected recipient vary by both mode of transmission and the specific circumstances

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A.    MODES OF TRANSMISSION
1-           Sexual transmission of HIV from an infected partner to an uninfected partner can occur through male-to-female, female-to-male, male-to-male, and female-to-female sexual contact. Worldwide, sexual transmission of HIV is the predominant mode of transmission.

2-         Parenteral transmission of HIV has occurred in recipients of blood and blood products, through transfusion of blood (estimated 95% risk of infection from transfusion of a single unit of HIV-infected whole blood [CDC, 1998a]) or clotting factors, in intravenous or injection drug users through the sharing of needles (approximately 0.67% risk per exposure [Kaplan, 1992]), in health care workers through needle sticks (approximately 0.3–0.4% risk per exposure, depending on the size and location of the inoculum [Updated PHS guidelines, 2001]), and, less commonly, mucous membrane exposure (0.09% risk per exposure (Updated PHS guidelines, 2001).

3-    Perinatal transmission can occur in utero, during labor and delivery, or post-partum through breast-feeding (Gwinn, 1996). Perinatal transmission rates average 25–30% (Blanche, 1989) overall in the absence of intervention, but vary by maternal stage of disease, use of antiretroviral therapy, duration of ruptured membranes, practice of breast-feeding, and other factors. In the United States as of December 2001, 91% of cumulative pediatric AIDS cases were attributed to perinatal transmission (CDC, 2002). More information on perinatal transmission can be found in Chapter VII on HIV and Reproduction.

B-FACTORS AFFECTING TRANSMISSION.
1-    Mutation of chemokine-receptor gene.
2-    Late stage of HIV infection.
3-    Primary HIV infection.
4-    Anti-retroviral therapy.
5-    Local infection.
6-    Method of contraception.
A-    Barrier decrease Infectiousness and Susceptibility.
B-    Spermicidal agents.
C-    Intrauterine devices.
7-    Factors that lower PH cervix of vagina that decrease HIV Concentration In Genital Secretions and Infectiousness.
8-    Immune activation which increase Infectiousness and Susceptibility.
9-    Genital tract trauma that increase Infectiousness.
10-    Pregnancy increase HIV Concentration in Genital Secretions and Infectiousness.