Highest transmission risk from blood and semen

Blood and semen of HIV infected people contain high concentrations of HIV. In vaginal fluid the concentration is significantly lower. The virus can also be present in other body fluids, such as saliva, sweat, tear drops and urine. The concentration in these fluids, however, is too low to be infectious.

Unsafe practices in relation to infected blood, semen and vaginal fluid can create a risk of infection. The virus can also be transmitted from mother to child, during pregnancy, at birth or after birth (through breastfeeding).

Possible transmission routes are manifold

HIV is known to be transmitted via the following routes:

• Through unprotected anal or vaginal sexual contact with an infected person. The risk of infection through heterosexual intercourse with an infected person is relatively small: around 0.1% per unprotected contact. The risk of transmitting the virus is higher for anal intercourse: 0.8%-3.0%. Also, the risk of transmission is higher from male to female. Finally, the risk is higher for the receptive sexual partner than for the insertive sexual partner (Holmberg et al., 1989).
• Through exposure to infected blood, by sharing contaminated needles or syringes (e.g. injecting drug users).
• Through transmission from mother to child, during pregnancy, birth or from breastfeeding. The risk of transmission depends on the number of virus particles in the mother’s blood.
• Through accidental puncture wounds acquired during the medical treatment of an HIV-infected patient. The risk of infection after such an injury is estimated at 0.3% (Gisselquist et al., 2006).
• Through blood transfusions and organ transplants. The risk of transmission through intravenous exposure to HIV infected blood is very high: 60-95%.The careful screening and selection of donors (those at risk of contracting HIV are asked not to donate their blood) now carried out virtually prevents the transmission of HIV through blood transfusions (Schreiber et al., 1996).

Transmission through spit and household contact (dinnerware, cutlery, bathroom hygiene) does not occur.

Transmission risk is greatest shortly after infection and several years later

The risk of transmission is highest shortly after infection and several years later, when the infection has become symptomatic. The prevalence of the infection and the risk of infection together determine whether transmission takes place per contact.

STI increase infection risk

The risk of infection is increased through simultaneous infection with other sexually transmitted infections (STI). Those infected with HIV are also more susceptible to contracting other STI and to a greater number of complications (Fleming & Wasserheit, 1999). The risk of HIV transmission is therefore greatly reduced where preventive measures are put in place to combat STI.