HIV and AIDS
What is HIV?
HIV stands for Human Immunodeficiency Virus. It was originally isolated in Paris in May 1983 by Luc Montagnier. It belongs to a group of viruses called retroviruses.
Viruses copy their genetic material into the genetic material of human cells. This means that infected cells stay infected for the rest of their lives.
Through mechanisms which are still not fully understood, HIV prevents the immune system from working properly. Normally, the body's immune system would fight off infection. But HIV is able to infect key cells (called CD4 cells) which co-ordinate the immune system's fight against infection. Many are actually destroyed by being infected. Others, including CD4 cells which are not themselves infected, no longer work properly.
What is AIDS?
AIDS stands for Acquired Immune Deficiency Syndrome. AIDS is the result of damage to the immune system. A damaged immune system is unable to protect the body against certain specific 'opportunistic' infections and tumours. These are called opportunistic because they are caused by organisms which are normally controlled by the immune system but which 'take the opportunity' to cause disease if the immune system has been damaged. The opportunistic infections which are considered to be 'AIDS-defining' are listed in the HIV & AIDS Treatments Directory. Unlike most other diseases, different people with AIDS may experience different clinical problems, depending on which specific opportunistic infections they develop. This is what a syndrome means – a collection of different signs and symptoms that are all part of the same underlying medical condition.
What is the link between HIV and AIDS?
It has generally been accepted throughout the scientific community for a number of years that infection with HIV is the necessary pre-condition for the development of AIDS.
It is evidently possible for an individual's immune system to be compromised in other ways, and in rare cases this can lead to the same kinds of infection as those seen in AIDS. This has been termed idiopathic CD4 lymphocytopenia or ICL. The immune suppression seen in ICL is not always the same as in AIDS however, often clearing up without treatment.
Although it is clear that HIV has a central role in the development of AIDS, it is not clear exactly what this role is. The human immune system is immensely complex and there are many ways in which it can be affected by a retrovirus such as HIV. Furthermore, it is also not clear what role (if any) other factors – known as co-factors – may play in the development of immune damage.
Transmission of HIV
HIV is present in the blood (including menstrual blood), semen and vaginal fluids of infected people, but can only be passed on to another person if those fluids get into his/her body. Although sophisticated laboratory techniques are able to isolate the virus from other body fluids of infected people, such as saliva, the level of virus in these fluids is far too low to be infectious.
Thus, the main ways in which HIV is transmitted are:
Through unprotected anal or vaginal sex. HIV is unable to pass through good quality condoms, such as those bearing the CE mark.
Through blood-to-blood contact. This mainly happens through the sharing of injecting equipment amongst injecting drug users. In the past, before screening was introduced in the UK, this also occurred through blood transfusions or from infected blood products, such as the Factor VIII used to treat hæmophilia. Very rarely it can happen through occupational accidents amongst healthcare workers, such as needlestick injuries. Fortunately, follow-up studies have shown that fewer than 1% of individuals who receive injuries with HIV-contaminated needles become infected
Vertically, from mother-to-baby during the course of pregnancy, birth or breast-feeding. The average risk of transmission during pregnancy is in the region of 10-15% if the mother is HIV-positive, although it may be higher if she has a higher viral load (the amount of HIV in her blood, which indicates the rate at which the virus is reproducing in the body) or has developed AIDS. Breast-feeding does carry a risk of transmission, and should be avoided in countries where good alternatives to the mother's milk are available.
The detection of HIV
Usually HIV infection is detected by an HIV antibody test. The first test to be done, usually on blood, but possibly on saliva, is an ELISA (Enzyme Linked Immunosorbent Assay). Since this test can sometimes be positive even when someone is not infected – a `false positive' result – a second test called the Western Blot is done. This can confirm an ELISA.
The amount of time between getting HIV infection and developing antibodies varies. The vast majority of people with HIV will produce antibodies by around 45 days after infection. However, in a small proportion it may take up to six months for antibodies to develop, and in a very few people with HIV infection it may take even longer. This is one reason why a lack of HIV antibodies does not always mean freedom from infection.
It is important to bear in mind that the HIV antibody test is not an 'AIDS test': there is no such thing. It is simply a test for one of the results of HIV infection. For instance, the fact that you can find antibodies to HIV in saliva does NOT mean that you can find virus there in any quantity. Nor does the test predict whether or not you will develop AIDS.
There are also a number of laboratory tests which can look for the virus or parts of the virus itself (antigen testing and PCR, Polymerase Chain Reaction, or viral load testing), or damage to the immune system, or other aspects of the body's response to the effects of the virus. These should not be confused with the HIV antibody test.
An antigen is a part of a virus that stimulates the production of antibodies. Someone who is antibody negative but antigen positive has the virus but has not yet produced antibodies.
Becoming HIV antibody positive
Most people who become infected with HIV do not notice that they have been infected. Some have a short illness soon after they become infected. This is called 'seroconversion illness' because it coincides with the time that blood tests for antibodies to HIV become positive. The illness may take the form of a sore throat, a fever or a rash, or, rarely, more severe illness.
Before the appearance of antibodies to HIV in the blood, some people may develop symptoms following exposure to HIV. Antibodies usually become detectable at the same time as this illness. This is known as seroconversion illness. The symptoms include:
- Prolonged fever (4 – 14 days) and aching limbs
- Red blotchy rash over the trunk
- Sore throat (pharyngitis)
- Ulceration in the mouth or genitals
- Severe headaches
- Aversion to the light.
Other symptoms, such as paralysis, meningitis and opportunistic infections as a consequence of severe immune suppression are much less common. Symptoms of seroconversion may occur in up to 80% of people infected, but the severity of the symptoms varies. Some people report only a mild flu–like illness 2 to 6 weeks after a risk of HIV exposure, but others experience an illness severe enough to require hospitalisation. The longer the illness lasts, and the more severe it is, the more likely you would be to develop AIDS within five years, presuming you were not to use antiretroviral therapy.
Remember that these symptoms could be caused by other infections; flu, glandular fever, tonsillitis and a serious herpes attack have similar symptoms to those reported in seroconversion illness.
If you think that you have been exposed to HIV in recent weeks and you develop some of these symptoms, treatment is an option that should be considered. However, we don't yet know whether this treatment will be of long–term benefit. If you want to begin such treatment, you should approach one of the major HIV treatment centres immediately. Do not wait to be referred by your GP, who may not understand the urgency of the need for treatment or the scientific rationale for intervening with drug treatment at this stage of infection. Some of the largest GUM clinics in London are now running studies to follow people treated at this stage of infection. If you live outside London, call your local clinic and ask to speak to a consultant to find out whether they will consider embarking on an experimental course of treatment.
Current British HIV Association guidelines recommend that treatment in acute infection is best initiated as part of a clinical trial.
Asymptomatic HIV infection
Initially any damage caused by HIV has no outward effect. This is called asymptomatic infection, which may last for many months or years.
Sometimes people with asymptomatic HIV infection may have swollen lymph nodes, which is called PGL, Persistent Generalised Lymphadenopathy. But this is not a sign of damage in itself.
People who have HIV and feel 100% well may nevertheless have signs of immune damage detectable by laboratory tests; for example, their CD4 count may be below normal levels. The use of viral load tests has also demonstrated that HIV is actively replicating inside the bodies of asymptomatic people from the moment of infection; at no time is the virus truly latent. The CD4 count and viral load are known as surrogate markers and are discussed in the HIV & AIDS Treatments Directory.
Symptomatic HIV Infection
Statistical studies of people with HIV have shown that the more time passes, the more likely it is that the damage will become more severe and infections or tumours may develop. However, such statistics reflect population tendencies: individuals will have their own responses to HIV which may or may not lead to symptomatic disease.
The infections are called opportunistic infections because they are infections with pathogens that are around us all the time – and which our immune systems can normally fight off with no problems. They only become a problem if the immune system is not working well, so that infections that were previously under control become reactivated.
Our bodies also contain cells that can go out of control at any given moment. Normally, these too are kept under control by our immune system. If, however, our immune system is damaged, these cells can cause opportunistic tumours or sometimes cancer.
In addition, HIV can have direct effects upon the body. For instance, the virus can also attack immune cells in the brain. These cells are involved in feeding the brain cells. If they are damaged, the brain, or some nerves, may not work as well as usual. This is called HIV-associated dementia.
When someone gets ill due to these infections or tumours, he or she is said to have symptomatic HIV infection.
It is important to understand that apart from the so–called 'wasting syndrome' and HIV-associated dementia, the symptoms of AIDS and of symptomatic HIV disease are the symptoms of particular conditions caused by opportunistic infections and tumours, and not directly by HIV itself. Therefore there are a wide range of possible symptoms, and it serves no particular function to answer the question: what are the symptoms of AIDS? Particular symptoms are associated with particular opportunistic infections.
An AIDS diagnosis
Before coming to a diagnosis of AIDS, doctors look at a variety of symptoms and tests. There is no single test for AIDS.
Doctors will look for one of the opportunistic infections or cancers in the presence of underlying immune deficiency. They might, for instance, do tests to try to seek a positive diagnosis of PCP, a type of pneumonia.
These tests are normally only available if you have already been diagnosed as HIV antibody positive, or sometimes if you are seriously ill.
The development of new and improved treatments both for the underlying HIV infection and the opportunistic infections has significantly altered the natural history of HIV and AIDS.
Early estimates of the proportion of people with HIV who will go on to develop AIDS were partly based on the experience of the epidemic in the years before such drugs became widely available. As new drugs against HIV and opportunistic infections have become available, these have had a dramatic impact on estimates of the average prognosis of people with HIV.
Improving treatments for opportunistic infections mean that it is increasingly possible to develop an AIDS-defining illness, such as PCP, and have it successfully treated. Thereafter the individual may, to all intents and purposes, be just as healthy as they were before developing PCP, but nevertheless will now have been diagnosed as having AIDS. In practice, this means that very many people who meet rigid AIDS definitions can continue to lead healthy lives for long periods.
Prophylaxis, to prevent infections recurring or happening even a first time, has also changed the natural history of HIV disease. A number of studies in the early 1990s showed that, compared with the 1980s, people with HIV were experiencing a shorter survival time after they developed AIDS than previously. The reason for this was that prophylactic drugs have delayed the onset of AIDS, so that people are receiving their AIDS diagnosis when their CD4 cell count falls to, say, 75, when earlier in the epidemic they might have developed an AIDS-defining illness at a CD4 count of nearer 200. People with HIV who use prophylaxis are living with HIV without symptoms, and without an AIDS diagnosis, for longer.
The most dramatic developments in HIV treatment have occurred since 1995. Substantial reductions in death rates among HIV-positive people have been reported in many developed countries where infected people have access to the latest therapies. Early use of today's antiretroviral therapies, before HIV-related symptoms develop, may reduce an individual's risk of developing an AIDS-defining illness. Furthermore, many people with very advanced disease, including those with a prior AIDS diagnosis, have experienced remarkable recoveries in physical health, accompanied by rising CD4 counts and a reduction in viral load.
How safe is oral sex?
There is a commonly held belief among lay people that oral sex carries no risk. In fact, some consider oral sex a safe sex alternative. But the truth is, like any other sexual activity, oral sex carries a risk of transmitting HIV and other sexually transmitted diseases. The risk is even greater in serodiscordant couples (one partner is HIV positive while the other is negative), people who are not monogamous, or in people who inject drugs and / or share needles. Truth be told, abstaining from oral, anal, and vaginal sex all together or having sex only with a mutually monogamous, uninfected partner is the only way that individuals can be completely protected from the sexual transmission of HIV.
What are the risks of oral sex?
Risk is classified as being documented(transmission that has actually occurred, been investigated, and documented in the scientific literature) or theoretical (passing an infection from one person to another is possible). While there is documented risk with engaging in oral sex with an HIV infected partner the risk is much less than with anal or vaginal intercourse. This fact makes it very hard to calculate the actual risk with oral sex. Another factor that makes risk determination difficult is the fact that most people who engage in oral sex also engage in other types of sexual practices, namely vaginal and anal intercourse. Still, there have been document cases of HIV transmission strictly from oral sex.
Theoretical Risk: In fellatio, there is a theoretical risk of transmission for the receptive partner because infected pre-ejaculate ("pre-cum") fluid or semen can get into the mouth. For the insertive partner there is a theoretical risk of infection because infected blood from a partner's bleeding gums or an open sore could come in contact with a scratch, cut, or sore on the penis. Documented Risk: Although the risk is many times smaller than anal or vaginal sex, HIV has been transmitted to receptive partners through fellatio, even in cases when insertive partners didn't ejaculate.
Theoretical Risk: Cunnilingus carries a theoretical risk of HIV transmission for the insertive partner (the person who is licking or sucking the vaginal area) because infected vaginal fluids and blood can get into the mouth. (This includes, but is not limited to, menstrual blood). Likewise, there is a theoretical risk of HIV transmission during cunnilingus for the receptive partner (the person who is having her vagina licked or sucked) if infected blood from oral sores or bleeding gums comes in contact with vulvar or vaginal cuts or sores. Documented Risk: The risk of HIV transmission during cunnilingus is extremely low compared to vaginal and anal sex. However, there have been a few cases of HIV transmission most likely resulting from oral-vaginal sex.
Theoretical Risk: Anilingus carries a theoretical risk of transmission for the insertive partner (the person who is licking or sucking the anus) if there is exposure to infected blood, either through bloody fecal matter (bodily waste) or cuts/sores in the anal area. Anilingus carries a theoretical risk to the receptive partner (the person who is being licked/sucked) if infected blood in saliva comes in contact with anal/rectal lining. Documented Risk: There has been one published case of HIV transmission associated with oral-anal sexual contact.