Acquired immunodeficiency syndrome or Acquired immune deficiency syndrome (AIDS) is a disease caused by a virus called HIV.

As of 2018, it is estimated that there are 39.7 million people worldwide infected with HIV.[1] The HIV pandemic is most severe in Sub-Saharan Africa. Over 60% of all people with HIV live in the region.

Many people with HIV do not know they have it. Because of this, the exact number of people with HIV is unknown.

Scientists believe the first human who got HIV was a person in Africa in the early 1900’s. It infected only a small amount of people (disease not recognised), until it then turned into an epidemic reported to have started in New York (USA) in 1981. It then very quickly started spreading to other countries. This happened when Simian Immunodeficiency Virus (SIV) went from apes or chimpanzees to humans. This virus probably crossed to humans when a hunter came into contact with monkey blood while cutting up monkeys to eat.[2] Research in October 2014 shows that the virus started in Kinshasa during the 1920s.[2] It was quickly spread by unprotected sex, dirty needles used by intravenous drug users, and it then made its way into the medical blood supply .[2] Some people described the spread of the disease as a sexidemic (widespread).[3]

Not everyone who has HIV has AIDS. When people first get HIV, they can be healthy for years.  A person is diagnosed as having AIDS when he or she gets specific types of illnesses or gets sick in certain ways due to their HIV.  Once a person's HIV progresses to (or turns into) AIDS, the person will continue to have AIDS for the rest of their life.  While there are many treatments for HIV/AIDS, at this point there is no cure.

If someone has HIV they are called HIV-positive.

Someone has AIDS if they have HIV and either:

If a person gets an "AIDS-defining illness," this is usually a sign that the person has AIDS.  Healthy people do not get these illnesses, because a healthy immune system is strong enough to fight off these diseases.  Because of this, getting an AIDS-defining illness is a sign that a person's immune system is seriously damaged.  In a person with HIV, getting an AIDS-defining illness signals that the HIV has damaged the immune system badly enough that the person now has AIDS.

Some AIDS defining illnesses are:

HIV can be spread by some body fluids that have HIV in them:[4]

This means a person can get HIV by:[4]

HIV is NOT spread by:[4]

There are medicines that help people with AIDS. These are called antiretroviral medicines (or antiretrovirals.) Anti- means against. HIV is a retrovirus. So antiretroviral means it fights retroviruses.

Antiretrovirals cannot cure AIDS. This means they cannot make all of the virus leave a person's body. But they can make people with AIDS more healthy. Antiretrovirals help people fight the HIV virus. This makes their immune systems work better. So antiretrovirals are a treatment but not a cure for HIV.

People with HIV/AIDS who take antiretroviral medicines live longer. They live longer without getting AIDS defining illnesses. But after a long time, the HIV virus learns how to fight the antiretrovirals. The HIV virus is not killed by this medicine. HIV becomes resistant to the medicine. Then the resistant HIV hurts the immune system and the person may get AIDS.

Sometimes when HIV is resistant to one medicine, another medicine can be used. To make less resistance happen, people with AIDS take more than one medicine at the same time. They may take 2–4 medicines at once. This is sometimes called a cocktail or AIDS cocktail.

When HIV gets resistant to one medicine, this is changed to another medicine. So the AIDS cocktail that people with AIDS take changes over time. But after a long time, the HIV learns to be resistant to many drugs. This is called multi-drug-resistant (acronym MDR) HIV. After the HIV in a person has MDR-HIV there may be no more medicines to treat them. So scientists keep trying to find new medicines to fight HIV.
The five most important HIV medicines are:

Many people who die of AIDS, especially in Africa, leave behind children who are still alive, and may need help. These children are called AIDS orphans.

There are many ways people fight the AIDS epidemic.

The most important way to stop HIV/AIDS is education. People can get HIV from the exchange of bodily fluids and from sharing needles. Children can also get HIV from their mothers (when they grow inside pregnant mothers and when they drink breast milk.)
Sex is one way to get HIV. If people use condoms when they have sex, there is a much smaller chance of catching HIV.

A person can also get HIV by sharing needles. This means using a needle that has not been cleaned after someone else has used it. Some people who take illegal drugs like heroin and cocaine take these drugs by needle. Some of these people share needles. If one person has HIV and he shares his needles, he can give HIV to other people. But if people have clean needles or if they know how to clean needles, they do not get HIV as much.

Many people do not know that condoms and clean needles help stop HIV. They may not even know that sharing needles and sex with someone who has HIV can make them get HIV. Even if people know about condoms and clean needles, they may not have condoms and clean needles.

There are some people who do not want people to know about condoms or clean needles. They believe that if people know about condoms and have condoms they will have more sex. They believe that if people have clean needles they will use illegal drugs more. Many of these people think this because of their religion. For example, the Catholic church does not want people to have or use condoms.[5]  They do not want people to have condoms because they do not think people should have sex unless they are married. They also think that married people should not use condoms, because they believe that if people have sex, they should be prepared to accept a possible pregnancy.

Scientists who study (look at and learn about) people who use condoms, see that if teenagers (children 13–19) learn about condoms (and other birth control) they have less unsafe sex. Scientists see that learning about these things does not make teenagers start having sex earlier. The teenagers also have safer sex. Safer sex means doing things (like wearing condoms) to try not to get pregnant or get sexually transmitted diseases (STDs or STIs) like HIV, gonorrhea, and syphilis. Using a condom works very well for keeping people from getting pregnant or getting STDs if people know how to use a condom the right way.[1] [2]

Scientists have also learned that if a city has a needle exchange program it will have fewer people who use illegal drugs. Needle exchange programs are where people can come in and trade dirty needles for clean needles. This means that if they use drugs they will be more safe. But needle exchange programs do more than give people clean needles. They teach people about drugs. If people want to stop using drugs, they help them.

The best way to stop HIV is thought to be a vaccine. There is no vaccine for HIV yet. Many scientists are looking for an HIV vaccine. Even one that protected some people from HIV would save millions of people's lives.

Some people think that HIV is not the cause of AIDS. They dispute the connection between HIV and AIDS,[6] the existence of HIV itself, or the validity of HIV testing and treatment methods.[7][8] These claims, known as "AIDS denialism", are rejected by the scientific community.[9] However, they have had a significant impact, particularly in South Africa. There the government's official embrace of AIDS denialism (1999–2005) was responsible for its weak response to that country's AIDS epidemic. It has been blamed for hundreds of thousands of avoidable deaths and HIV infections.[10][11][12]

Some conspiracy theories have been put about. Operation INFEKTION was a worldwide Soviet active measures operation to spread the claim that the United States had created HIV/AIDS. Surveys show that a significant number of people believed – and continue to believe – in such claims.[13]