What is HIV/AIDS? People have been warned about HIV and AIDS for over twenty years now. AIDS has already killed millions of people, millions more continue to become infected with HIV, and there's no cure - so AIDS will be around for a while yet. However, some of us still don't know exactly what HIV and AIDS actually are.
HIV - Human Immunodeficiency Virus
What is HIV?
HIV - Human Immunodeficiency VirusHIV is a virus. Viruses infect the cells of living organisms and replicate (make new copies of themselves) within those cells. A virus can damage the cells it replicates in, which is one of the things that can make an infected creature become ill.
People can become infected with HIV from other people who already have it, and when they are infected they can then go on to infect other people. Basically, this is how HIV is spread.
HIV stands for the 'Human Immunodeficiency Virus'. Someone who is infected with HIV is said to be 'HIV+' or 'HIV positive'.
Why is HIV dangerous?
The immune system is a group of cells and organs that protect your body by fighting viruses and infections. The human immune system usually finds and kills viruses fairly quickly.
So if the body's immune system attacks and kills viruses, what's the problem?
Different viruses attack different parts of the body - some may attack the skin, others the lungs, and so on. The common cold is caused by a virus. What makes HIV so dangerous is that it attacks the immune system itself - the very thing that would normally get rid of a virus. It particularly attacks a special type of immune system cell known as a CD4 lymphocyte. And on top of this, HIV has a number of tricks that help it to evade the body's defences, including very rapid mutation. This means that once HIV has taken hold, the immune system can never fully get rid of it.
There isn't any way to tell just by looking if someone's been infected by HIV. But a blood test can detect infection from about three months after the virus first entered the body. A person infected with HIV may look and feel perfectly well for many years and may not know that they are infected. But as the person's immune system weakens they become increasingly vulnerable to illnesses, many of which they would previously have fought off easily.
And what's AIDS?
A damaged immune system is not only more vulnerable to HIV, but also to the attacks of other infections. It won't always have the strength to fight off things that wouldn't have bothered it before.
As time goes by, a person who has been infected with HIV is likely to become ill more and more often until, usually several years after infection, they become ill with one of a number of particularly severe illnesses. It is at this point that they are said to have AIDS - when they first become seriously ill, or when the number of immune system cells left in the body drops below a particular point. Different countries have slightly different ways of defining the point at which a person is said to have AIDS rather than HIV.
AIDS (Acquired Immune Deficiency Syndrome) is an extremely serious condition, and at this stage the body has very little defence against any sort of infection.
How long does HIV take to become AIDS?
Without drug treatment, HIV usually progresses to AIDS in an average of ten years. This average, though, is based on a person having a reasonable diet. Someone in a resource-poor area who might not be adequately nourished may well progress to AIDS and death much more rapidly.
HIV antiretroviral medication can prolong the time between HIV infection and the onset of AIDS. Modern combination therapy is highly effective and, theoretically, someone with HIV can live for a long time before it becomes AIDS. These medicines, however, are not widely available in many poor countries around the world, and millions of people who cannot afford or access medication continue to die.
How is HIV passed on?
HIV is found in the blood and the sexual fluids of an infected person, and in the breast milk of an infected woman. HIV transmission occurs when sufficient of these fluids get inside someone else's body. There are various ways a person can become infected with HIV.
Ways in which you can be infected with HIV :
Unprotected sexual intercourse with an infected person
Sexual intercourse without a condom is risky, because the virus, which is present in an infected person's sexual fluids, can pass directly into the body of their partner. This is true for unprotected vaginal and anal sex. Oral sex carries a lower risk, but again HIV transmission can occur here if a condom is not used - for example, if one partner has bleeding gums or an open cut, however small, in their mouth.
Contact with an infected person's blood
If sufficient blood from an infected person enters the body of an uninfected person then it can pass on the virus.
From mother to child
HIV can be transmitted from an infected woman to her baby during pregnancy, delivery and breastfeeding. There are special drugs that can greatly reduce the chances of this happening, but they are unavailable in much of the developing world.
Use of infected blood products
Many people in the past have been infected with HIV by the use of blood transfusions and blood products which were contaminated with the virus - in hospitals, for example. In much of the world this is no longer a risk, as blood donations are routinely tested.
Injecting drugs
People who use illegal injected drugs are also vulnerable to HIV infection. In many parts of the world, often because it is illegal to possess them, injecting equipment or works are shared. A tiny amount of blood can transmit HIV, and can be injected directly into the bloodstream with the drugs.
It is not possible to become infected with HIV through :
sharing crockery and cutlery
insect / animal bites
touching, hugging or shaking hands
eating food prepared by someone with HIV
toilet seats
HIV Myths
the world, there are a number of different myths about HIV and AIDS. Here are some of the more common ones :
'You would have to drink a bucket of infected saliva to become infected yourself' . . . Yuck! This is a typical myth. HIV is found in saliva, but in quantities too small to infect someone. If you drink a bucket of saliva from a positive person, you won't become infected. There has been only one recorded case of HIV transmission via kissing, out of all the many millions of recorded cases. In this case, both partners had extremely badly bleeding gums.
'Sex with a virgin can cure HIV' . . . This myth is common in some parts of Africa, and it is totally untrue. The myth has resulted in many rapes of young girls and children by HIV+ men, who often infect their victims. Rape won't cure anything - and is a serious crime all around the world.
'It only happens to gay men / black people / young people, etc' . . . This myth is false. Most people who become infected with HIV didn't think it'd happen to them, and were wrong.
'HIV can pass through latex' . . . Some people have been spreading rumours that the virus is so small that it can pass through 'holes' in latex used to make condoms. This is untrue. Latex blocks HIV, as well as sperm - preventing pregnancy, too.
What does 'safe sex' mean?
Safe sex refers to sexual activities which do not involve any blood or sexual fluid from one person getting into another person's body. If two people are having safe sex then, even if one person is infected, there is no possibility of the other person becoming infected. Examples of safe sex are cuddling, mutual masturbation, 'dry' (or 'clothed') sex . . .
In many parts of the world, particularly the USA, people are taught that the best form of safe sex is no sex - also called 'sexual abstinence'. Abstinence isn't a form of sex at all - it involves avoiding all sexual activity. Usually, young people are taught that they should abstain sexually until they marry, and then remain faithful to their partner. This is a good way for someone to avoid HIV infection, as long as their partner is also completely faithful and doesn't infect them.
What is 'safer sex'?
Safer sex is used to refer to a range of sexual activities that hold little risk of HIV infection.
Safer sex is often taken to mean using a condom for sexual intercourse. Using a condom makes it very hard for the virus to pass between people when they are having sexual intercourse. A condom, when used properly, acts as a physical barrier that prevents infected fluid getting into the other person's bloodstream.
Is kissing risky?
Kissing someone on the cheek, also known as social kissing, does not pose any risk of HIV transmission.
Deep or open mouthed kissing is considered a very low risk activity for transmission of HIV. This is because HIV is present in saliva but only in very minute quantities, insufficient to lead to HIV infection alone.
There has only been one documented instance of HIV infection as a result of kissing out of all the millions of cases recorded. This was as a result of infected blood getting into the mouth of the other person during open mouthed kissing, and in this instance both partners had seriously bleeding gums.
Can anything 'create' HIV?
No. Unprotected sex, for example, is only risky if one partner is infected with the virus. If your partner is not carrying HIV, then no type of sex or sexual activity between you is going to cause you to become infected - you can't 'create' HIV by having unprotected anal sex, for example.
You also can't become infected through masturbation. Nothing you do on your own is going to give you HIV - it can only be transmitted from another person who already has the virus.
Is there a cure?
HIV medication can slow the progress of the virus. Worryingly, surveys show that many people think that there's a 'cure' for AIDS - which makes them feel safer, and perhaps take risks that they otherwise shouldn't. These people are wrong, though - there is still no cure for AIDS.
There is antiretroviral medication which slows the progression from HIV to AIDS, and which can keep some people healthy for many years. In some cases, the antiretroviral medication seems to stop working after a number of years, but in other cases people can recover from AIDS and live with HIV for a very long time. But they have to take powerful medication every day of their lives, sometimes with very unpleasant side effects.
But there is still no way to cure HIV, and at the moment the only way to remain safe is not to become infected.
In this computer generated image, the large object is a human CD4+ white blood cell, and the spots on its surface and the spiky blue objects in the foreground represent HIV particles.HIV stands for Human Immunodeficiency Virus. Like all viruses, HIV cannot grow or reproduce on its own. In order to make new copies of itself it must infect the cells of a living organism.
HIV belongs to a special class of viruses called retroviruses. Within this class, HIV is placed in the subgroup of lentiviruses. Other lentiviruses include SIV, FIV, Visna and CAEV, which cause diseases in monkeys, cats, sheep and goats.
What does HIV look like?
Outside of a human cell, HIV exists as roughly spherical particles (sometimes called virions). The surface of each particle is studded with lots of little spikes.
An HIV particle is around 100-150 billionths of a metre in diameter. That's about the same as:
*0.1 microns
*4 millionths of an inch
*one twentieth of the length of an E. coli bacterium
*one seventieth of the diameter of a human CD4+ white blood cell.
Unlike most bacteria, HIV particles are much too small to be seen through an ordinary microscope. However they can be seen clearly with an electron microscope.
The structure of HIV
The proteins gp120 and gp41 together make up the spikes that project from HIV particles, while p17 forms the matrix and p24 forms the core.HIV particles surround themselves with a coat of fatty material known as the viral envelope (or membrane). Projecting from this are around 72 little spikes, which are formed from the proteins gp120 and gp41. Just below the viral envelope is a layer called the matrix, which is made from the protein p17.
The viral core (or capsid) is usually bullet-shaped and is made from the protein p24. Inside the core are three enzymes required for HIV replication called reverse transcriptase, integrase and protease. Also held within the core is HIV's genetic material, which consists of two identical strands of RNA.
What is RNA?
Almost all organisms, including most viruses, store their genetic material on long strands of DNA. Retroviruses are the exception because their genes are composed of RNA (Ribonucleic Acid).
RNA has a very similar structure to DNA. However, small differences between the two molecules mean that HIV's replication process is a bit more complicated than that of most other viruses.
How many genes does HIV have?
HIV has just nine genes (compared to more than 500 genes in a bacterium, and around 20,000-25,000 in a human). Three of the HIV genes, called gag, pol and env, contain information needed to make structural proteins for new virus particles. The other six genes, known as tat, rev, nef, vif, vpr and vpu, code for proteins that control the ability of HIV to infect a cell, produce new copies of virus, or cause disease.
At either end of each strand of RNA is a sequence called the long terminal repeat, which helps to control HIV replication.
How does HIV replicate?
This electron microscope photo shows newly formed HIV particles budding from a human cell.
Entry
HIV can only replicate inside human cells. The process typically begins when a virus particle bumps into a cell that carries on its surface a special protein called CD4. The spikes on the surface of the virus particle stick to the CD4 and allow the viral envelope to fuse with the cell membrane. The contents of the HIV particle are then released into the cell, leaving the envelope behind.
Reverse Tran*****ion and Integration
Once inside the cell, the HIV enzyme reverse transciptase converts the viral RNA into DNA, which is compatible with human genetic material. This DNA is transported to the cell's nucleus, where it is spliced into the human DNA by the HIV enzyme integrase. Once integrated, the HIV DNA is known as provirus.
Tran*****ion and Translation
HIV provirus may lie dormant within a cell for a long time. But when the cell becomes activated, it treats HIV genes in much the same way as human genes. First it converts them into messenger RNA (using human enzymes). Then the messenger RNA is transported outside the nucleus, and is used as a blueprint for producing new HIV proteins and enzymes.
Assembly, Budding and Maturation
Among the strands of messenger RNA produced by the cell are complete copies of HIV genetic material. These gather together with newly made HIV proteins and enzymes to form new viral particles, which are then released from the cell. The enzyme protease plays a vital role at this stage of HIV's life cycle by chopping up long strands of protein into smaller pieces, which are used to construct mature viral cores.
The newly matured HIV particles are ready to infect another cell and begin the replication process all over again. In this way the virus quickly spreads through the human body. And once a person is infected, they can pass HIV on to others in their bodily fluids.
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