How Did AIDS Start?

Medically Reviewed on 6/3/2022
How Did AIDS Start?
People with AIDS have damaged immune systems, leading to severe illnesses called opportunistic infections.

Acquired immunodeficiency syndrome (AIDS) is the last stage of a disease caused by two lentiviruses, human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2).

Origin of HIV

  • Most emerging diseases affecting humans come from wildlife; it is often human behavior that is to blame for the spillover.
  • Human immunodeficiency virus (HIV) infection is no exception. The virus responsible for attacking the immune system is zoonotic, which means it transferred to humans from nonhuman primates (a type of chimpanzee, subspecies Pan troglodytes) in Central and West Africa.
  • The chimpanzee version of the virus called simian immunodeficiency virus (SIV) was probably passed to humans when humans hunted these chimpanzees for meat and came in contact with their infected blood.
  • The earliest known case of HIV-1 infection in human blood is from a sample taken in 1959 from a man who died in Kinshasa in the Belgian Congo (now Kinshasa in the Democratic Republic of the Congo) in the 1920s.
  • Over decades, HIV has slowly spread across Africa and later into other parts of the world. The virus has shown its existence in the United States since the mid to late 1970s.

Bushmeat practice

According to the natural transfer theory (hunter theory), the plausible explanation for the cross-species transmission of SIV or HIV (post mutation) is that the virus was transmitted from an ape or monkey to a human when a hunter or bushmeat vendor was bitten while hunting or butchering the animal. The resulting exposure to blood or other bodily fluids of the animal resulted in an HIV infection.

2 types of HIV

  1. HIV-1: More virulent, easily transmitted and is the cause of most human immunodeficiency virus (HIV) infections globally.
  2. HIV-2: Less transmittable and is largely confined to West Africa.

What are the symptoms of HIV?

People may have flu-like symptoms within two to four weeks after getting infected (acute human immunodeficiency virus infection), lasting for a few days or several weeks.

Symptoms may include:

How does HIV spread?

Initially, symptoms can be mild. Hence, people with human immunodeficiency virus (HIV) infection might not know they are infected and can spread HIV to others without knowing it.

HIV can spread

HIV does not spread through

  • Pee, poop, spit, vomit, or sweat 
  • Coughing or sneezing
  • Holding hands or touching
  • Sharing eating utensils or drinking glasses


A Timeline of the HIV/AIDS Pandemic See Slideshow

3 stages of human immunodeficiency virus (HIV) infection

Stage I: Acute HIV infection

  • A huge number of HIV is present in the blood, making the person contagious.
  • The body’s natural response to infection is shown by flu-like symptoms.
  • Only antigen or antibody tests or nucleic acid tests can diagnose acute infection.

Stage II: Chronic HIV infection

  • Also called asymptomatic HIV infection or clinical latency that may last a decade or longer, but some may progress faster.
  • HIV is active but reproduces at low levels.
  • People remain asymptomatic during this phase though they can transmit HIV to others unknowingly.
  • At the end of this phase, the amount of HIV in the blood (viral load) goes up and the CD4 cell count goes down.
  • Symptoms may begin as the person moves into stage III.
  • People who have taken HIV medicine as prescribed may never move into stage III.

Stage III: Acquired immunodeficiency syndrome (AIDS)

  • The last and most severe phase of HIV infection.
  • People with AIDS have damaged immune systems, leading to severe illnesses called opportunistic infections.
  • The diagnosis of AIDS is confirmed when the CD4 cell count drops below 200 cells/mm or the presence of certain opportunistic infections.
  • A high viral load makes the person extremely infectious.
  • If left untreated, the survival period is approximately three years.

8 ways to protect yourself from HIV

  1. Avoid intercourse with an unknown partner
  2. Be in a monogamous relationship
  3. Use a condom every time you have sex (anal, oral, and vaginal)
  4. Do not share needles
  5. Reduce the number of sexual partners
  6. Get regularly tested for human immunodeficiency virus (HIV) and make sure all partners do too
  7. Get tested and treated for other sexually transmitted diseases (STD); having an STD increases the risk of HIV infection
  8. Use condoms even if you are infected to prevent infection by another strain of HIV

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Medically Reviewed on 6/3/2022
Image Source: iStock image

KidsHealth. How Do People Get AIDS?

Sharp PM, Hahn BH. Origins of HIV and the AIDS pandemic. Cold Spring Harb Perspect Med. 2011;1(1):a006841. A Timeline of HIV and AIDS.

Centers for Disease Control and Prevention. About HIV.