HIV is a viral infection that weakens the immune system. HIV came from a type of virus in chimpanzees called the simian immunodeficiency virus (SIV). It likely spread to humans after they came into contact with the blood carrying the infection after hunting chimpanzees for food.

HIV is a sexually transmitted infection (STI) that a person can acquire via contact with bodily fluids.

When someone has exposure to the virus, it can cause changes to the cells, which can then lead to their cells creating more of the virus. It damages the immune system, making it easier for a person to contract an infection.

However, advancements in treatments can allow an individual living with HIV to suppress the virus, slow its progression, and maintain immune system function.

Although treatment cannot cure HIV, it can reduce a person’s viral load to become undetectable. This means they are unlikely to transmit HIV to others. This also helps the immune system recover, making someone less susceptible to contracting opportunistic infections.

This article looks into the etiology of HIV. It also looks at the history of HIV and how it causes infection in the body.

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According to the Centers for Disease Control and Prevention (CDC), HIV came from a type of chimpanzee that lived in Central Africa.

There are two types of HIV — HIV-1 and HIV-2 — and their exact origins differ according to the type.

HIV-1 is a more virulent type, which means that it spreads easily. HIV-1 is the type of HIV that has a global presence. It originated in Central Africa.

In contrast, HIV-2 is less virulent and not as common. It originated from West Africa.

Both types relate to an immunodeficiency virus, called SIV, that is present in a type of chimpanzee.

The CDC states that humans most likely contracted SIV after coming into contact with blood carrying the infection after hunting the chimpanzees for meat.

Humans may have contracted HIV from chimpanzees as early as the 1800s. And over the years, it has spread throughout Africa and other parts of the world. HIV has been present in the United States since approximately the 1970s.

The CDC provides the following timeline for HIV in the U.S.:

YearWhat happened?Cases of HIV
1980–1984A new disease appeared, and researchers found that HIV could transmit via:

• sexual activity
• donated blood
• injection drug use
• pregnancy
There were:
• 42,000 people with HIV
• 20,000 new HIV cases
1985–1989The CDC issued safeguards for blood supplies.There were:
• 420,000 people with HIV
• 130,400 new HIV cases
1990–1994The CDC issued regulations for healthcare workers after a healthcare worker contracted HIV.
Safeguarding regulations expanded into other businesses and community organizations.
There were:
• 735,000 people with HIV
• 84,200 new HIV cases
1995–1999Health officials issued guidelines to help prevent opportunistic infections and introduced highly active antiretroviral therapy.
The death rates for AIDS declined.
There were:
• 750,000 people with HIV
• 48,800 new HIV cases
2000–2004The U.S. emphasized HIV prevention for those with HIV.
Global AIDS programs and funding increased.
There were:
• 897,000 people with HIV
• 55,300 new HIV cases
2005–2009The CDC provided HIV prevention and testing recommendations. They also launched HIV campaigns, and global programs expanded.There were
• 1,067,000 people with HIV
• 55,400 new HIV cases
2010–2014Those who were not citizens of the U.S. with HIV were allowed to enter the country.
Preexposure prophylaxis (PrEP) helped prevent transmission, while treatment helped reduce viral loads.
There were:
• 1,172,700 people living with HIV
• 43,742 HIV diagnoses
2015–2020PrEP holds its promise, and people have more data about HIV transmission.
The data on HIV diagnoses shows progress and challenges.
There were:
• 953,690 people living with HIV
• 39,393 HIV diagnoses

HIV is a type of virus called a retrovirus, which inserts a copy of its RNA into a cell’s DNA. The change it makes to the cell’s DNA causes the cell with the infection to create new copies of the retrovirus.

The new retroviruses go on to cause infections in new cells, changing their DNA and repeating the process.

Without treatment, a person living with HIV will eventually develop AIDs, making secondary infection from viruses, bacteria, and other organisms more likely.

A person can contract HIV via contact with bodily fluids.

The majority of people acquire HIV from:

  • anal sex
  • vaginal sex
  • sharing needles and syringes

Individuals can also contract HIV via pregnancy, during birth, and breastfeeding.

Several factors can increase the likelihood that a person receives exposure to HIV.

Some common risk factors of coming in contact with HIV include:

  • anal or vaginal sex without using a barrier method
  • sharing needles
  • the presence of another STI
  • accidental needle sticks injuries, particularly in healthcare workers
  • unsterile injections or transfusions

Learn more about the chances of contracting HIV.

The following are statistics about HIV:

  • At the end of 2020, approximately 37.7 million people worldwide were living with HIV.
  • From 2015 to 2019, the number of new cases in the U.S. decreased by 9%.
  • At the end of 2019, an estimated 1,189,700 people in the U.S. are living with HIV.
  • In 2019, of those living with HIV in the U.S., about 87% knew they had it.
  • Male-to-male sexual transmission accounts for 65% of new cases.
  • Heterosexual sexual transmission accounts for about 23% of new cases.
  • Drug use accounts for about 7% of new cases.
  • In 2019, the number of deaths from any cause of people living with HIV was 15,815.

A person can take some steps to help prevent acquiring HIV from another individual.

Some recommendations to prevent infection include:

  • using male or female condoms when having penetrative sex
  • undergoing testing for other STIs
  • never sharing needles with others
  • taking PrEP and postexposure prophylaxis if someone is at risk of infection

Pregnant people living with HIV should take HIV medications as a doctor prescribes to help prevent transmitting HIV to the fetus.

After birth, a doctor will administer 4–6 weeks of HIV medications to a baby who has a biological parent with HIV. This reduces the risk of transmitting HIV to the baby to 1% or less.

HIV came from a type of chimpanzee that lived in Central Africa. Humans may have come into contact with blood carrying this virus when they hunted the animal for food. The virus became present in the U.S. in the 1970s.

HIV is a type of virus that causes changes to the cells in the person’s body. The changes to the cells cause the altered cells to produce more of the virus, which can eventually cause an individual to lose immune system functioning.

Although there is no cure, treatment can help. A person can often keep the virus from replicating and restore or maintain immune function. However, there is no cure, so they will often require treatment for the rest of their life.