However, the presence of HIV in bodily fluids alone does not mean that contact with such fluids will definitely lead to contamination. For this to happen, two conditions must be met:
- A suitable route of transmission;
- A sufficient quantity of the virus.
A quantity of the virus (viral load) high enough to transmit HIV can only be found in the blood, seminal fluid, vaginal secretions and at a very low percentage in breast milk.
Other fluids can only be considered to present a risk if they are contaminated with blood, but most of the time transmission cannot take place because the concentration of HIV is too low. A subject who has contracted the infection in one way, for example contact with infected blood, could transmit HIV in another way, for example through sexual intercourse.
HIV is primarily transmitted through sex
The sexual transmission of AIDS represents the most common way that HIV is transmitted worldwide. HIV can be transmitted by either homosexual or heterosexual sex and, in the case of the latter, it is more commonly transmitted from men to women (around 20%) than from women to men (less than 3%). However, it is difficult to define with certainty what the percentage risk of contagion is following sexual intercourse; certain people could contract HIV following a single sexual encounter, while other people will never be contaminated even after years of sexual intercourse with an HIV-positive partner.
There are actually a number of factors that influence the possibility of transmission following a sexual encounter:
- The risk can be increased by the number of events of sexual contact if the illness is at an advanced stage, by any genital diseases, and by the use of oral contraceptives in women.
- The risk can be reduced by using a condom, spermicides, or even if the person contaminated with HIV is taking antiretroviral therapy.
There are different behaviours that represent risk factors for the sexual transmission of HIV:
- Multiple sexual partners;
- Sexual intercourse with high-risk people (prostitutes, drug addicts);
- Not using a condom;
- Different types of sexual activities;
- Psychological conditions: taking drugs or drinking alcohol could impair judgement, and therefore the wherewithal to use suitable protection in the case of high-risk encounters.
Transmission via blood
People who work in medical facilities or with drug addicts are at risk because they are more likely to come into contact with infected blood and therefore become infected with HIV themselves. Prevention is therefore extremely important. A simple cut or scrape could represent a risk if it comes into contact with infected blood.
That said, HIV is a virus that doesn’t last very long in the outside environment and can only survive for two to three days, even under favourable conditions. The viral load of infected fluid can reduce by more than 90% in a few hours when it dries. In the event of an accidental injury involving contaminated material, certain factors come into play in determining whether contamination will occur:
- The viral load of the residual blood;
- The type of instrument involved in the potential contamination;
- The duration of contact and depth of the injury;
- The subject’s pre-existing injuries and immune condition.
Following accidental exposure to infected blood, the risk of contracting HIV is around 0.2-0.3%.
Transmission via injection
The parenteral route (via injection) is the easiest way for HIV to be transmitted from one person to another; the transmission rate via the parenteral route can be as much as 90%. This is due to the fact that this means that HIV reaches the bloodstream directly, where it directly finds a number of mononuclear cells (lymphocytes and monocytes). The main risk factor for parenteral transmission is drug addiction. This method of contamination takes place through the sharing of needles infected with HIV.
Other practices such as tattooing and piercing also present risk factors for AIDS; any item that could pass the skin barrier is capable of transmitting HIV.
HIV can be transmitted from mother to child, specifically during:
- Pregnancy, through the placenta;
To reduce the risk of infecting the newborn, a caesarian is generally performed in the case of HIV-positive women, and they are advised not to breastfeed.
Taking medications during pregnancy and after childbirth can considerably reduce the risk of the child being infected. However, if the child does contract HIV, it will begin to produce the antibody itself and will also be seropositive.
Last updated: 16/10/2017