The human immunodeficiency virus is a retrovirus (Retroviridae family) that contains RNA and affects the immune system by attacking CD4+ T-lymphocytes, macrophages and dendritic cells. HIV attaches to the CD 4+ receptors expressed on the surface of these cells and enters their nucleus where with the help of the enzyme reverse transcriptase synthesizes DNA and replicates. Occurs viremia and the HIV spreads throughout the body.
There are two types of HIV distinguished – HIV-1 and HIV-2. HIV-1 is more common, whereas HIV-2 is mainly found in West Africa.
HIV infection is a sexually transmitted disease, so no wonder that more than half of the cases of HIV contraction are associated with sexual intercourse.
As at 2012, in the USA and 6 dependent areas (according to CDC) diagnoses of HIV by transmission were:
- 64% – due to male-to-male sexual contact;
- 17% – heterosexual contact (females);
- 9% – heterosexual contact (males);
- 4% – injection drug use (males);
- 3% – injection drug use (females);
- 3% – male-to-male sexual contact + injection drug use;
- 1% – other (including hemophilia, blood transfusions, perinatal exposure etc.)
Body fluids that contain viruses
- Semen, pre-seminal fluid, ejaculate;
- Vaginal fluids;
- Breast milk;
- Rectal fluids.
Saliva, sweat, tears, urine and feces when not contaminated by blood DO NOT contain viruses.
- Male-to-male sexual contact was reported to be the main transmission route in the USA (approximately 49%).
- Heterosexual contact
Having a vaginal or oral sex without using a condom is one of the most spread transmission routes. Receptive anal sexual intercourse puts a person at the highest risk of getting infected. However, it is possible to catch HIV from insertive anal sex as well.
Although oral sex is considered less risky, in some cases, HIV may be caught through oral sex, especially when the mucous membranes of the mouth have sores, are traumatized or the gums are bleeding. The same applies to deep, open-mouth kissing (regarding both partners).
Transmission by blood and blood products
90-100% of those who are exposed to HIV-contaminated products get infected.
- Injection drug use (IDU)
Sharing needles, syringes, the water in which drugs are mixed, or the cotton through which drugs are filtered with an infected person puts you at risk of contracting HIV. According to the CDC, about 7% of HIV positive persons were infected by injection drug use in the USA.
- Blood transfusions, blood products or organ transplantation
Although this route is very rare in developed countries as before any procedures all the blood-containing products are being carefully checked for HIV and other infections. It was estimated that currently the risk of infection with HIV in the United States by transfusion of checked blood is approximately 1 in 1.5 million donations.
- Direct contact between wounds, broken skin or mucous membranes and infected blood, blood-contaminated body fluids or other infected body fluids.
- Reused or not properly sterilized needles or other equipment used for piercing or tattoo.
Health care workers and laboratory workers are at risk of getting infected when they are injured with needles of sharp medical instruments. However, that risk is relatively low – HIV transmission after a skin puncture from a needle or a sharp object that was contaminated is approximately 0.3% and after a mucous membrane exposure – 0.09%
The child may be infected while still in the womb, during the delivery or by breastfeeding.
- The transmission during pregnancy is relatively rare (especially if the mother-to-be receives antiretroviral treatment) as the mother’s blood and the blood of the fetus do not mix. When the prophylactic antiretroviral therapy is not administered to the mother during pregnancy, labor, and delivery, and to the fetus after birth, the possibility of HIV transmission from mother to infant/fetus is from 15 to 35% depending on the country.
- The highest risk (50-65%) of infecting the child occurs during vaginal delivery, so the Cesarean section is recommended to protect the child.
- Breastfeeding by an HIV-positive mother should be avoided when it’s possible as breast milk contains viruses.
HIV is NOT transmitted by:
- Sharing foods and drinks;
- Sharing toilets;
- Sharing towels;
- Shaking hands;
- Closed-mouth kissing;
- Insects or pets;