What are HIV and AIDS?

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1. What are HIV and AIDS
2. The immune system and HIV
3. HIV statistics

What are HIV and AIDS?

HIV stands for Human Immunodeficiency Virus. It is a virus that attacks and weakens the immune system. If it is untreated, HIV causes so much damage that the body is no longer able to defend itself.

People who have been infected with HIV are often referred to as being HIV-positive (sometimes this is written as HIV+, or even +ve). Although there have been many advances in treatment in recent years, there is still no cure for HIV infection. Once you have been infected with HIV, you will always be HIV-positive.

HIV is the virus that can lead to AIDS. AIDS stands for Acquired Immune Deficiency Syndrome and is characterised by the appearance of the opportunistic infections (infections like tuberculosis which take advantage of a weakened immune system) that are a result of HIV infection.

If you are diagnosed with HIV early, and respond well to treatment, AIDS may be kept at bay.

The name 'AIDS' was more appropriate many years ago, when doctors did not fully understand the late stages of HIV infection. Today we know that AIDS is not a syndrome at all, because a syndrome is a collection of symptoms that do not have an easily identifiable cause. A more current name for the illness caused by the late stages of HIV infection is HIV disease. However, AIDS is still the name that most people use to refer to the immune deficiency caused by HIV.

As treatment for HIV infection becomes more effective, fewer people in the UK are now given an AIDS diagnosis.

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The immune system and HIV

HIV attacks the immune system. Your immune system is your body's defence against many illnesses and diseases and is crucial in maintaining your health. Your immune system's basic task is to distinguish between your body's own cells and anything alien to it, such as viruses, fungus, bacteria, toxins and foreign tissue.

To respond to these unwanted invaders, your body has a variety of mechanisms and specialist cells. Your skin is your first line of defence and a vital part of the immune system. It not only forms a barrier against intruders, but tells the rest of your immune system to get to work if there is a breach (e.g. an open wound).

Skin provides such a good barrier that most invaders have to get inside your body by being inhaled or swallowed. Some infections can also enter through mucous membranes (such as the moist tissue in your mouth, arse and cock). Once inside your body they can get into your bloodstream and quickly circulate.

Fortunately, your immune system has special immune cells called white blood cells. While many parts of your body play a role in the immune system (such as the tonsils, spleen and intestine), the white blood cells have a variety of important roles which organise how your body deals with intruders.

White blood cells

Different white blood cells have different jobs. Some white blood cells can attack a range of different foreign organisms. Others are able to recognise a single, specific foreign organism to which your body has been exposed in the past.

Large white blood cells (called phagocytes) act like a general patrol. They eat up debris and foreign organisms in your body and alert specialised cells to the presence of intruders.

These specialised cells include T lymphocytes, which can activate your immune system in response to danger, and B lymphocyte cells which manufacture antibodies. An antibody can lock on to a distinctive part of an intruder. When this happens, the antibody signals to other white blood cells to attack.

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Immune system 'memory'

The immune system has a kind of memory that keeps a history of the illnesses you've been exposed to in the past. Once an antibody is produced in response to a specific intruder – a specific flu virus, for example – you have cells that immediately recognise it and tell your immune system to attack. This is how vaccines work. They teach your body to look out for an attacking organism even though you've never been infected by it.

HIV's attack

Your body is under constant attack from outside invaders and your immune system is on a thorough search-and-destroy mission which keeps most illness at bay. Occasionally, your immune system needs to declare a state of emergency and go on full attack.

However, if you have HIV, your immune system is less in control. HIV is a virus that not only survives the immune system's attack; it also does battle with it. In order for the virus to reproduce, it uses parts of your white blood cells and destroys them in the process. This means that a constant stream of new white blood cells is being called for to help. HIV also damages your gut. This results in some swallowed bacteria leaking from the gut into the bloodstream, which means that even more white blood cells are needed to fight. It's as if your entire immune system is working overtime and over the years it can wear out. This process can be monitored by doctors who check declining levels of a certain type of immune cell called CD4 cells.

Anti-HIV drugs help to prevent the virus from multiplying so that your immune system can continue to function and keep you as healthy as possible.

Without anti-HIV drugs, your immune system's 'memory' is eventually destroyed and so you can get serious infections which your body would usually know how to deal with.

HIV statistics

By the end of 2010 the estimated number of people in the UK living with HIV was 91,500, of whom around 24% remain undiagnosed and were therefore unaware of their infection.

1 It is also estimated that 40,100 gay men in the UK were living with HIV. 1
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HIV infection rates

It's very difficult to know how many people have become infected with HIV in any one year. Most people don't find out they have HIV until some time after they become infected, so for example some people who were infected during the last twelve months may not be diagnosed for several years. However it's possible to analyse blood samples from people newly diagnosed with HIV, to find out if they were recently infected. Research suggests that of the approximately 3,000 gay men diagnosed with HIV in 2010, one in four acquired their infection recently.

2
It's easier to measure the number of people diagnosed with HIV every year by counting the number of positive HIV test results. You will sometimes hear news reports which state "The number of people infected with HIV has increased…", but what they are usually talking about is the number of people diagnosed with HIV.

HIV diagnoses in gay men from 1996 – 2011 (as of January 2012) 3

*Note: Data for 2011 is only for the first half of the year.

Numbers may rise as further reports are received, particularly for recent years.
In addition to the steady stream of new infections that occur each year there are more people than ever before coming forward to test, which has increased the number of new diagnoses for several years.
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AIDS diagnoses

Effective drugs to manage HIV infection allow people with HIV to live longer and they are less likely to develop AIDS than they were in the early 1990s. This means fewer people are now dying due to HIV infection than previously.

Deaths and AIDS diagnoses in gay men in the UK from 1995 – 2010 (as of January 2011) 3

*Note: Data for 2011 is only for the first half of the year.

Numbers may rise as further reports are received, particularly for recent years.
The reduction in deaths among people with HIV, coupled with the new infections that happen every year, means that there are more people living with HIV in the UK than ever before. You are much more likely to know someone with HIV than you were ten years ago, even if you don't realise it.

Gay men accessing HIV-related care in the UK from 2000 – 2009 (as of August 2010) 4

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References:
1 Health Protection Agency (HPA). HIV in the United Kingdom: 2011 report. Health Protection Agency, November 2011.

2 Health Protection Agency (HPA). Sexually transmitted infections in men who have sex with men in the UK: 2011 report. Health Protection Agency, November 2011.

3 Health Protection Agency (HPA). Men who have sex with men: United Kingdom new HIV diagnoses to end of June 2011. Health Protection Agency, January 2012.

4 Health Protection Agency (HPA). HIV-diagnosed persons seen for HIV care: survey of prevalent HIV infections diagnosed (SOPHID): men who have sex with men (MSM) data tables. Health Protection Agency, 2011.

 

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