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HIV modes of transmission

Each of the three HIV transmission modes have their own peculiarities:

Sexual transmission

Most HIV infections have been or are acquired during unprotected sex. Sexual transmission is through contact between sexual secretions (or blood contaminated with the virus) and genital mucosa, rectum or mouth. Transmission probality varies depending on the type of sexual activity with an infected person ranging from 0,00005 to 0,005 per sexual act, compared to 0.0067 for sharing a syringe with a HIV positive drug addict and 0.9 for blood transfusion with HIV contaminated blood. The best protection against HIV regarding this mode of transmission is the condom. Following the synthesis of several studies, it has shown that the proper use of condoms during each sexual activity lowers the risk of infection by 85%.

Transmission through blood

This mode of contamination concerns especially injecting drug users, hemophiliacs and transfusion recipients. Health professionals (health nurses, laboratories) are also concerned, though more rarely. Do not overlook the risks of contamination by not or poorly disinfected needles (tattoos).

Transmission from mother to child during pregnancy

Mother to child transmission of the virus can occur in utero in the last weeks of pregnancy and at delivery. Note a tendency to false HIV positiveness among multiparous. Without treatment, the rate of transmission between mother and fetus, is close to 20%. Breastfeeding is also a risk of contamination for the newborn, about 5%, which makes it inadvisable for infected mothers. However, three recent studies, one led by PJ. Illife et al. in Zimbabwe, another by H. Coovadia in South Africa, and a last one by Mr. Sinkala et al. in Zambia, shows that exclusive early breastfeeding reduces the overall risk of postnatal transmission to 4% and increases the survival rate of children. Currently available treatments allies with a programmed caesarean have reduced this rate to 1%. The results are more mixed in developing countries, the risk of postnatal transmission has been reduced using Nevirapine down to 13% according to HIVNET012, 18% according to Quaghebeur et al.


HIV virus infecting a cell