Modes of transmission of HIV/AIDS

According to Markowitz (2007), HIV is transmitted by four main routes:

  • Sexual contact,
  • Exposure to infected body fluids or tissues
  • From mother to child
  • Sharing of hypodermic needles

i.        Sexual contact

The most frequent mode of transmission of HIV is through sexual contact with an infected person. The majority of all transmissions worldwide occur through heterosexual contacts (i.e. sexual contacts between people of the opposite sex); however, the pattern of transmission varies significantly among countries. In the United States, as of 2009, most sexual transmission occurred in men who had sex with men with this population accounting for 64% of all new cases (Sepkowitz, 2010).

Risk of transmission increases in the presence of many sexually transmitted infections and genital ulcers. Genital ulcers appear to increase the risk approximately fivefold. Other sexually transmitted infections, such as gonorrhoea, Chlamydia, trichomoniasis, and bacterial vaginosis, are associated with somewhat smaller increases in risk of transmission (Evian, 2006).

  1. Exposure to infected body fluids or tissues

The second most frequent mode of HIV transmission is via blood and blood products. Blood-borne transmission can be through needle-sharing during intravenous drug use, needle stick injury, transfusion of contaminated blood or blood product, or medical injections with unsterilised equipment.

Unsafe medical injections play a significant role in HIV spread in sub-Saharan Africa. In 2007, between 12 and 17% of infections in this region were attributed to medical syringe use. The World Health Organization estimates the risk of transmission as a result of a medical injection in Africa at 1.2%. Significant risks are also associated with invasive procedures, assisted delivery, and dental care in this area of the world. People giving or receiving tattoos, piercings, and scarification are theoretically at risk of infection (Sepkowitz, 2010).

iii.        From mother-to-child

HIV can be transmitted from mother to child during pregnancy, during delivery, or through breast milk resulting in infection in the baby. This is the third most common way in which HIV is transmitted globally. In the absence of treatment, the risk of transmission before or during birth is around 20% and in those who also breastfeed 35%. With appropriate treatment the risk of mother-to-child infection can be reduced to about 1%. Preventive treatment involves the mother taking antiretrovirals during pregnancy and delivery, an elective caesarean section, avoiding breastfeeding, and administering antiretroviral drugs to the newborn (Sepkowitz, 2010).

iv       Sharing of hypodermic needles

Sharing of hypodermic needles leads to the spread of HIV/AIDS. According to Cohen and Hellmann (2015),at the start of every injection, blood is introduced into the needle and syringe. Therefore, a needle and syringe that an HIV-positive person has used can contain blood with the virus in it. Transmission occurs when another person then uses the same syringe without cleaning it. The reuse of a blood-contaminated needle or syringe by another person can be an effective means of transmission because a large quantity of blood can be injected directly into the bloodstream.

Markowitz (2007) stated that although HIV does not generally survive well outside the body, it can survive for long periods of time (over 28 days) if hermetically sealed in syringe. There is a risk of HIV infection through intravenous injecting, subcutaneous injecting (injecting into the fat under the skin) and intramuscular injection.

CDC (2012) stated that HIV infection from blood can occur in other ways as a result of injecting drug use:

  • Through sharing water used to flush blood out of a needle and syringe.
  • Through sharing syringes that have been cleaned in a way that does not eliminate all the blood they contain.
  • Through reusing bottle caps, spoons or other containers used to dissolve drugs in water and to heat drug solutions.
  • Through unsafe disposal of needles or syringes used for injecting drugs, leading to accidents in which blood gets into the body of another person.


Centre for Diseases Prevention and Control (CDC) (2012). Opportunistic infections and Kaposi’s sarcoma among Haitians in the United States.MMWRMorb Mortal WklyRep. ,31 (26), 353–354.

Cohen, M. S. & Hellmann, S. C. (2015).HIV prevention in clinical care settings: 2014 recommendations of the International Antiviral Society-USA Panel. JAMA: the Journal of the American Medical Association, 312 (4), 390–409.

Evian, C. (2006). Primary HIV/AIDS care: a practical guide for primary health care personnel in a clinical and supportive setting (Updated 4th ed.). Houghton: Jacana

Markowitz, M. (2007).Primary HIV-1 infection is associated with preferential depletion of CD4+ T cells from effector sites in the gastrointestinal tract. J. Exp. Med. 200 (6): 761–70.

Sepkowitz, K. A. (2010). AIDS—the first 20 years. N. Engl. J. Med., 344 (23), 1764–72.

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