How HIV/AIDS spreads
You can get infected with HIV if blood or body fluids such as semen or vaginal fluid from someone with HIV enters your body.
Unprotected sex is the major mode of transmission of HIV worldwide.
The virus doesn’t survive very long outside the body. This means that you cannot get HIV from, for example, touching an object that an HIV-positive person has touched.
HIV is spread…
1. Through unprotected vaginal, anal or oral sex with an HIV-infected person.
2. From an HIV-positive mother to her baby during pregnancy, childbirth or breastfeeding.
The risk of HIV passing from mother to child is approximately 15-45% if no preventative measures are taken. With interventions to prevent mother-to-child transmission, this risk is reduced to below 5%.
Interventions involve treating the HIV-positive mother as early as possible (during pregnancy or breastfeeding) and providing the HIV-exposed baby with prophylactic ART from birth or during breastfeeding (if the mother was diagnosed during this time) to reduce their risk of getting HIV.
3. Through contact with HIV-positive blood (e.g. when a healthcare worker is involved in a needle-prick accident).
4. When intravenous drug users share needles, blades or syringes.
5. Through the use of contaminated surgical instruments (e.g. during traditional circumcision).
6. Through blood transfusions with infected blood.
Note that, in South Africa, blood donated for blood transfusions is screened for HIV and that contaminated blood is discarded.
This means that the probability of HIV infection via blood transfusion is low. But transmission can still occur – even these highly sensitive tests can’t always detect very early HIV infection in a donor.
The risk of transmission
Infection isn’t inevitable if you’ve been exposed to HIV. The likelihood of transmission is determined by, for example, the concentration of HIV in the other person’s body fluids.
Although HIV has been detected in saliva, the concentration is thought to be too low for HIV to be transmitted through French kissing.
It would require the exchange of almost one litre of saliva between individuals before there would be sufficient virus available for possible transmission. In addition, a digestive protein in human saliva tends to inactivate the virus.
The risk of HIV transmission also depends on the HIV-positive sexual partner’s stage of infection. Virus concentrations in blood and body fluids are highest when a person has been infected with HIV recently, or otherwise very late in the disease, when AIDS has developed.
Very soon after infection, the virus can multiply rapidly as the immune system hasn’t had time to respond and fight back yet; late in the disease, the virus can multiply rapidly because it has destroyed the immune system.
You’re more vulnerable to contracting HIV through sexual contact if you have sores on the genitals, mouth or around the anus/rectum. These sores can be caused by rough intercourse, other sexually transmitted infections (STIs), gum disease or overuse of spermicides.
In heterosexual sex, women are more vulnerable to HIV infection because of the large mucous-membrane surface area of the vagina compared to that of the penile opening. Men who are circumcised have a slightly lower risk of being infected with HIV.
Fortunately, you can take action to reduce your risk of infection. For example, using a male or female condom every time you have sex significantly reduces the risk of HIV infection and other STIs (as opposed to having unprotected sex). Birth-control methods such as hormonal oral contraceptives, implants, injections or intra-uterine contraceptive devices DO NOT reduce the risk of HIV infection.
Note that once you have HIV, your blood, semen or vaginal fluids will be infectious for the rest of your life.
Sexual behaviours and the risk of HIV
Very low risk
- Kissing (if no blood is exchanged through cuts or sores)
- Touching (such as stroking, hugging or massage)
- Masturbation (including mutual masturbation)
- Oral sex on a man with a condom
- Oral sex on a woman with a barrier method (such as plastic wrap, dental dam or a condom
- cut open to make a square)
- French kissing (the risk is higher when sores or gum disease are present)
- Vaginal sex with a male or female condom
- Anal sex with a male or female condom
- Anal sex without a condom
- Vaginal sex without a condom
- Always practise safe sex
Practising safe sex is important, even if both partners have HIV. This is because you and your partner could have different strains of the virus. If you have unprotected sex, you could infect one another with another strain.
Your immune system then has to fight off two different viruses and you may have to change your treatment regimen because different HIV strains require different drugs.
The four stages of HIV/AIDS
Although HIV infection can theoretically be divided into four different phases, these phases are not, in practice, as distinct.
If you’re HIV positive, your health will depend on how strong your immune system is, your CD4 cell count and viral load, and on whether you’ve been exposed to other infections and diseases.
HIV infection can, however, be divided into the following broad phases or stages:
Stage 1: The primary HIV infection phase
The acute phase of HIV infection (also called acute seroconversion illness) begins as soon as seroconversion has taken place. Seroconversion is when your HIV status converts or changes from being HIV-negative to HIV-positive. Prior to seroconversion, an HIV test would be negative. Following seroconversion, the HIV test would show that you’re HIV-positive.
The time between the onset of HIV infection and the appearance of detectable antibodies is known as the ‘window period’. This period lasts for a couple of weeks. During this time, an HIV test would show that a person is HIV-negative even though they’ve been infected with the virus. This is why a follow-up HIV test is always recommended if you have a negative HIV test.
About 30% - 60% of HIV-infected people develop ‘flu-like symptoms such as a sore throat, headache, mild fever, fatigue, muscle and joint pains, swelling of the lymph nodes, rash and (occasionally) oral ulcers. These symptoms usually last for a week or two.
Because the virus replicates rapidly, the viral load is usually very high during this acute phase.
Stage 2: The asymptomatic latent phase
The second phase of HIV infection is the asymptomatic latent or silent phase. During this stage, an infected person displays no (or very few) symptoms. During this phase, many HIV-positive people are unaware of the fact that they’re carrying the virus – unless they’ve had an HIV test and know their status. This means that they can unwittingly infect new sexual partners.
If you’re HIV-positive and in this second, latent phase, the virus is still active in your body. Over time, however, the virus will start to destroy your immune system. The good news is that most people (especially those who are on ART) remain HIV-positive for many years without any manifestation of clinical disease.
Stage 3: The minor symptomatic phase of HIV disease
In the third phase of infection, minor and early symptoms usually start to appear. At this stage, your viral load is increasing, your immune system begins to fail, and opportunistic infections occur.
If you’re in this phase, you may experience:
- Mild to moderate swelling of the lymph nodes in the neck, armpits and groin
- Occasional fevers
- Oral candidiasis (thrush)
- Pulmonary tuberculosis
- Oral hairy leukoplakia (causing white patches on the tongue)
- Shingles (or herpes zoster)
- Skin rashes and nail infections
- Sores in the mouth that come and go
- Recurrent upper respiratory tract infections
- Weight loss of up to 10% of your usual body weight
- General feelings of tiredness and not feeling well
Stage 4: AIDS
The fourth stage is known as Acquired Immunodeficiency Syndrome (AIDS).
Major symptoms and opportunistic diseases begin to appear as your immune system continues to deteriorate and the viral load gets higher. At this point, your CD4 count drops significantly (below 200) and your viral load becomes very high (between 100,000 and 1 million).
The following symptoms usually indicate advanced immune deficiency:
- Oral and vaginal thrush infections (thrush) that are persistent and recurrent
- Oesophageal candida (thrush in the food pipe)
- Extra-pulmonary tuberculosis (TB) that affects other parts of the body besides the lungs
- Recurrent herpes infections such as cold sores (herpes simplex)
- Recurrent herpes zoster (or shingles)
- Bacterial skin infections and skin rashes
- Bacterial pneumonia
- Kaposi’s sarcoma, a form of skin cancer
- Pneumocystis jerovici pneumonia (PJP) – the most common opportunistic infection in people with HIV
- Fever for more than a month
- Persistent diarrhoea for more than a month, leading to wasting syndromeWeight loss of more than 10% of usual body weight
- Generalised lymphadenopathy, a disease affecting the lymph nodes (or, in some cases, the shrinking of previously enlarged lymph nodes)
- Toxoplasmosis of the brain (an infection caused by a common parasite)
- Cytomegalovirus (a common herpes virus)
- Cryptococcal meningitis (an infection of the tissues covering the brain and spinal cord)
- Peripheral neuropathy (damage to the nerves in the hands and feet)
- Abdominal discomfort
- Oral hairy leucoplakia (white patches on the tongue)
- Persistent cough and reactivation of tuberculosis
Course and prognosis of HIV/AIDS
HIV attacks the CD4 (T-helper) cells that protect the body from infection.
When someone first contracts HIV, the virus spreads rapidly through the body and an intensive phase of viral replication results in high quantities of the virus and a corresponding decrease in CD4 count. This is the acute primary infection phase (also called “seroconversion illness”).
As the body’s immune responses begin to kick in and antibodies are produced, the amount of virus declines and the immune system recovers (shown by an increase in the CD4 count).
The clinical latency phase
During the clinical latency phase (when you look and feel healthy), the immune system controls the replication of the HI virus. Over time, however, the immune system weakens.
This is indicated by another decrease in the CD4 count while the viral load (the amount of HIV in the body) remains at a relatively low and stable level.
This clinical latency phase can vary from weeks to years.
Progression to AIDS
How rapidly HIV progresses to AIDS depends on a number of factors, one of which is the viral set point. This is the level of HIV in the blood established after initial infection.
Someone with a low viral set point (a small amount of HIV in the blood) is less likely to develop advanced disease quickly, while someone with a high viral set point (a high level of virus in the blood) is likely to show more rapid disease progression.
Nutrition, stress levels, and other lifestyle factors can influence disease progression.
Progression from HIV infection to AIDS follows a set pattern, although the rate of progression varies from person to person:
- Rapid progressors take 3 - 6 years
- Average progressors take 8 years
- Slow progressors take 15 years
- A small group of people are classified as non-progressors. The slow progression of these individuals is thought to be a result of genetically inherited factors.
Currently, there’s no cure for HIV/AIDS, but available anti-retroviral treatment (ART) can greatly extend years and quality of life. Treatment is also available to prevent and/or cure some of the illnesses associated with AIDS.
Reviewed by Dr Pooja Balani, MBBS (UK). Medical Technical Advisor at the Southern African HIV Clinicians Society. March 2018.