How can the transmission of HIV be prevented?

What is HIV?

HIV stands for Human Immunodeficiency Virus.  A virus can only survive by living in the cells of another organism. HIV is a type of virus called a retrovirus: It incorporates itself into the genetic material of cells called 'CD4 white blood cells', which are part of  the immune system.  This process is called 'reverse transcription', and it enables HIV to replicate.  This leads to destruction of the CD4 cells and damages the immune system.

What is AIDS?

AIDS stands for Acquired Immune Deficiency Syndrome.  A syndrome is a set of signs and symptoms that occur together, as a result of a specific cause.  The syndrome of AIDS is caused by HIV.  However a person infected with HIV may not necessarily progress to having AIDS.

HIV causes AIDS by damaging the immune system and making the body vulnerable to 'opportunistic infections'.  These are called ‘opportunistic’ because the weakened immune system gives them the ‘opportunity’ to take hold. These infections can cause death in people were severely weakened immune system.

AIDS was first diagnosed in 1981. Since then HIV and AIDS have spread rapidly and cases have been reported in more than 150 countries.  At the beginning of 2004 it was estimated that nearly 42,000,000 people were living with HIV and AIDS.

In Australia at the beginning of 2004, more than 20,000 people have been diagnosed with HIV infection. Over 8000 of these have been diagnosed with AIDS, and nearly 6000 people have died from AIDS related illnesses.

More statistics about HIV and AIDS...

How is HIV transmitted?

Unprotected sexual contact or sharing drug injecting equipment are the most common causes of HIV transmission. Sexual contact that may transmit HIV includes vaginal and anal sex, and with lower associated risk, oral sex.

In a some cases, HIV can be transmitted from pregnant mother to child. This is called ‘vertical transmission’. The risk of vertical transmission can be reduced if the mother uses anti-HIV drugs during pregnancy and delivery. In Australia breast feeding is not recommended for mothers infected with HIV because of the risk of HIV being transmitted through breast milk.

Healthcare workers and emergency personnel are at low risk of acquiring HIV from workplace exposure to HIV (for example by needlestick injury). A drug treatment regime called Post Exposure Prophylaxis (‘PEP’) has been shown to be effective in preventing seroconversion to HIV in these circumstances.

Blood products have been screened for HIV in Australia since 1985 and receiving transfusions of blood products is considered safe.

There is no evidence of transmission of HIV through ordinary social contact. HIV is not transmitted through sharing of plates, cups, cutlery, swimming pools or toilets, kissing, coughing, sneezing or spitting . The necessary conditions for HIV transmission (see below) are not present in these situations.

The principles of HIV transmission

Transmission of HIV is dependant on a number of conditions being fulfilled.  Understanding these conditions gives a better understanding of how HIV is transmitted:

Firstly there must be a source of HIV infection.  HIV exists in certain bodily fluids of persons infected with HIV.  These include blood, semen, vaginal fluid and  breast milk.

Secondly, there must be a way for HIV to be transmitted to the bloodstream of an uninfected person.  Sexual contact, or sharing drug-injecting equipment are the most common routes of HIV transmission.

Thirdly, there must be a person susceptible for infection.  HIV transmission only takes place from one human to another.  Mosquitoes, for instance cannot become infected with HIV and pass it on to humans.

Finally, a sufficient amount of HIV must enter the blood of an uninfected person for infection to be established.  If insufficient HIV enters the bloodstream, transmission of HIV infection will not occur.

If these conditions are not fulfilled, HIV transmission does not take place.

Stages of HIV infection

Seroconversion and primary illness

Some people can become infected with HIV without knowing it.  Other people may experience a short ‘seroconversion’ illness between two and six weeks after becoming infected.  The symptoms of this illness may be quite non-specific and include tiredness, fever, diarrhoea, rash, and ‘flu like symptoms.  These symptoms are common in other illnesses and so may not be remarkable at the time of the illness.

Asymptomatic HIV infection

Following seroconversion there may be a period of months or years during which HIV infection damages the immune system but does not manifest in outward signs or symptoms.  Some people may however experience a persistent swelling in the lymph nodes.  This period is known as ‘asymptomatic infection.’  During this time there is a constant battle taking place  between the immune system and HIV.

Symptomatic HIV infection

Indications of symptomatic HIV infection may include lack of energy, fevers and night sweats, persistent thrush in women and prolonged bouts of diarrhoea.

Late stage disease (equivalent to AIDS)

During advanced stages of HIV infection, a person may develop any of a number of infections which are considered as indicators of AIDS.  These are the conditions on which a diagnosis of AIDS, in a person who has HIV, is based.  They include:

• Kaposi’s Sarcoma (KS)
• Pneumocystis Carinii Pneumonia (PCP)
• Toxoplasmosis
• Cytomagalovirus disease (CMV)
• Candidiasis (thrush) in the oesophagus, throat or lungs

Testing and diagnosis of HIV

HIV infection is detected by a blood test for HIV antibodies.  Antibodies to HIV will not be detectable immediately after HIV infection, because it takes a while for measurable quantities of HIV antibodies to be produced by the immune system (up to three months).  This period is known as the ‘window period’.  An antibody test taken during the window period therefore may not be accurate.  This is important to remember, especially when making decisions about safe sex.

It is standard procedure to offer people pre and post HIV test counselling to the seeking an HIV antibody test.  This is regardless of the outcome of the test.  Counselling is done to explain the implications of the test results.

More information about testing and diagnosis...

Treating HIV and AIDS

In Australia, treatment of HIV and HIV related illnesses have usually followed four principles:

• Targeting the virus itself, using antiviral drugs.
• Treating and where possible preventing the individual opportunistic infections which result from damage to the immune system. caused by HIV.
• Restoring or rebuilding the damaged immune system.
• Treating and alleviating the symptoms of HIV disease.

In the 1980s and the early 1990s there were not a wide range of drugs available to target HIV itself, and those that were available often had limited effectiveness and unpleasant side effects.  In the latter 1990s there was a surge in the variety and effectiveness of anti-HIV drugs available in Australia, and the outlook since then has been more optimistic.

It is now common practice to combine several different classes of anti-HIV drugs in a treatment regime.  This has significantly improved the outlook for people living with HIV and AIDS, although problems with side effects are still reported.

Treatments are also available to reduce the risk of HIV transmission from pregnant mother to child, and where exposure to the risk of HIV transmission has occurred.

A significant addition to effective anti-HIV drugs has been the development of accurate tests to monitor the activity of HIV in a person’s body.  CD4 cell counts measure the number of CD4 cells in the blood.  Viral load tests measure the amount of HIV in the blood.  Together these have been very useful in determining how to best use anti-HIV drugs in treatment.

More information about HIV/AIDS treatments...

Preventing transmission of HIV

HIV Transmission can be prevented by:

• Practicing safe sex:  this means using condoms with water based lubricant for vaginal and anal intercourse.  Oral sex presents a lower risk for HIV transmission, and this can be reduced by using condoms and dental dams
• Not sharing drug injecting equipment: this includes syringes, spoons, filters, water, water containers and tourniquets. Sterile equipment for injecting drugs is freely available through needle exchange programmes.
• PEP (Post-exposure prophylaxis).  This is a course of anti HIV drugs which may prevent transmission of HIV after a risk exposure.
• Infection control in health and care care settings:  there are a number of standard guidelines that are followed in these settings to prevent infection (not just with HIV).  These are  effective in preventing HIV transmission.
• Infection control in other settings:  tattooing , body piercing and hairdressing procedures are required to comply with infection control guidelines, and standards for sterilising equipment.
• Prevention is better than cure: understanding the information in this document can help you to practice HIV prevention.