AIDS means Acquired (not hereditary, but caused by a virus) Immune (immunity system) Deficiency (lack, absence) Syndrome (group of symptoms and signs that shape an illness).
AIDS is an illness caused by the progressive damage of the immunity system caused by a virus called HIV (Human Immunity Deficiency Virus). This virus attacks the immunity system, which is the defence method against external aggressions of viruses, bacterium, microscopic funguses, and parasites.
The immunity system acts in whole body for the sake of the lymphocytes. A kind of them, those called T4, manage the operations for the defence, so they have an essential role. The destruction of this immunity system exposes the person to infections and tumours. The HIV attacks T4 lymphocytes mainly, so the system is paralysed before it can organise its defences.

Virus cycle:

The HIV can not live by itself. It has to do it inside a cell. This virus has as a particularity that invades and destroys the T4 lymphocytes mainly, which are the ones that manage the immune answer. T4 co-ordinate the rest of cells that take part in the defence. When the virus has already attacked, it can have two evolution. It can remain slept: then the cell keeps on living as it used to do. The infection persists but the patient doesn't show symptoms. This person's infected T4 cells can be transmitted to other people and infect them. The other evolution takes place when the virus becomes active and it reproduces itself inside the cell. Then, this cell blasts and it liberates a big number of viruses that will infect other T4. When there is a big quantity of infected T4 cells and they have been destroyed, defences are already weak. The risk that AIDS symptoms appear is higher then.

How the AIDS virus is transmitted?

The infection can only take place when enough quantity of viruses located in blood, semen, vaginal secretions and mother milk, get in other person's blood, through wounds, pricks, skin lesions, and vaginal, anal or mouth mucus. The HIV can live only for a short time outside the organism. That's why it has to penetrate into the exposed person's blood torrent. Besides, this transmission needs a minim quantity of viruses (threshold) to be an infection as well. Under this threshold, the organism is able to liberate itself from virus and it avoids that the virus stays.

Which are the ways of transmission?

The HIV is located in all of the infected person's internal fluids both external. But only some of them are able to infect. In order that this infection happens a minim quantity of viruses is required. This is, only only some of those fluids have quantity enough or they are over the required threshold level to provoke an infection.

Blood way:Sharing injection material or other stuff that have direct contact with an infected person's blood -as it happens with the use of injected drugs- has a high risk for an infection. When a prick or a cutting with any instrument that is recently contaminated with an infected person's blood occurs, this contact may suppose a risk of infection. But if these instruments have been properly disinfected or sterile, then there's no risk of infection.
Sharing personal stuff that can involve blood contact, such as toothbrush or shavers, is not recommended. The whole of the blood donations in developed countries pass a sanitary control, so the risk of infection is practically nonexistent. The organ donations in cases of transplants and the semen donation in cases of artificial insemination, are also controlled nowadays.

Sexual way:Semen and vaginal fluids are other kind of fluids that can transmit the HIV.

Among the different sexual practises, not all of them have the same risk:
- Unprotected anal / vaginal intercourse has a high risk of infection, both for active and passive partner. Withdrawall doesn’t avoid the risk of infection as little wounds can be produced during the practise.

- Oral sex: the risk exist when semen or vaginal fluids are kept in the mouth or they are swallowed, because there can be wounds on mouth or pharynx mucus. It has to be noticed that there is a big quantity of lymphocytes in the throat and pharynx, so it’s easy for the infection to take place. Real risk is mainly for the people who have an active role, those who do the fellatio or the cunnilingus.
- Other sexual practises (kissing, mutual masturbation, stroking,...) don't have any risk of infection.

If there are STD's, the risk of HIV infection is higher.

How AIDS virus is detected?

It can be detected by a blood sample analysis. The detection test is made by E.L.I.S.A. test, a method that detects antibodies that have been produced by the organism as an answer to the virus presence. A negative result means that the person hasn't produced the anti-HIV antibodies. A positive result is not enough to say someone is positive, it has to be made other checking in order to eliminate any possibility of a mistake. This more specific test is called Western Blot, and a positive result from it (practised with the same blood sample) indicates that the person is positive. A negative result says that the person is negative.

It's important to know that last risky sexual practise have had to haken place three months before the test at least. This time is know as 'window period'.

What does being positive mean?

A positive result doesn't mean that the person has AIDS, but he/she has the virus and he/she can transmit it by blood or sexual secretions. This person has to take the necessary precautions to reduce the risk of evolution towards AIDS and to avoid other people's exposition to the virus.

What happens when someone is positive and which can his/her evolution be?

We can separate three phases that can take place after the infection:

- prime infection: people who are infected begin to produce anti-HIV antibodies that will can be detected by serologic test. These people become, then, positive.

- evolution: in a second phase of the infection, between from 6 months to 10 years or even more, clinic manifestations can be appear in some people. Other can have an evolution towards AIDS (serious state of the HIV infection), and other can remain without symptoms. Small symptoms of the HIV infection can be persistent clinic manifestations such as anglions size increase in many parts of the body, loosing more than 10% of the body weight, night fever and sweating, serious herpes and persistent diarrhoea in abundance. These symptoms aren't caused by AIDS only- a lot of not serious illnesses can provoke these same manifestations. People who have a low number of T4 lymphocytes are at a higher risk to develop AIDS.

AIDS: those who will develop AIDS, because their immunity system is seriously damaged, can present the following manifestations:

• opportunistic infections
  
• some kinds of cancers (lymphoma, sarcoma of Kaposi)
  
• others: neurological diseases, slimming symptoms, etc.
  

Other people can remain without symptoms: it's clear that a number of positive men and women can remain being in a incubation period for more than 10 years, but they could develop the illness later, as the incubation time is unknown yet.

Treatment against HIV infection and AIDS:

Specific treatments against AIDS virus is called Antiretroviral Treatment. These try to avoid the virus can reproduce itself inside the infected cells. During the reproduction virus process, three enzymes take part:

• reverse transcriptase, which is divides in analogous and not analogous
  
• integrase
  
• protease

Antiretroviral substances action is focused in trying to make difficult or avoid these enzymes actions. Nowadays, a combination of two or three kinds of substances blocking two or three enzymes, or even blocking one enzyme in two different ways, can let the virus reproduction stops inside the infected cell. This is called Mixed Treatment. Nowadays, drug combinations cause a falling in the viral load values up to 99% -it is, one thousand times less viruses in blood than when treatment was begun. This lets a lot of people start the immunologic recovery, a slow but constant one. This way, the person is in a lower risk of suffering opportunistic infections and their effects, although virus can't be completely eradicated by now.

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