The 7 HIV Life Cycle Stages Explained

The human immunodeficiency virus (HIV) is a virus that attacks the body’s immune system. HIV infection begins with an acute stage (intense reaction) and may progress to chronic (ongoing). At its most advanced stage, HIV can cause acquired immunodeficiency syndrome (AIDS). However, there are now treatments available to prevent the progression of the virus.^1-3

HIV targets the body’s CD4 cells. These cells are also called T-cells or lymphocytes. Lymphocytes work to fight infection. Specifically, HIV destroys CD4 cells, which lowers the immune system’s ability to protect itself. Consequently, the person with HIV then becomes more at risk of serious illnesses and cancers.^1-4

How is HIV transmitted?

HIV passes from 1 person to another through certain body fluids. The infected fluid passes through mucous membranes to reach the bloodstream. For instance, blood, semen, vaginal fluids, and breast milk can all contain HIV. The most common methods of transmitting HIV include:¹

• Unprotected anal or vaginal sexual intercourse
• Sharing of needles
• Childbirth
• Breastfeeding

Tears, saliva, and sweat cannot transmit HIV. Kissing cannot usually transmit HIV. However, transmission may occur if blood or open wounds are present around the mouth. Hugging and other casual physical contact will not transmit HIV. Furthermore, neither will sharing food or using the same toilet seat pose a risk.¹

HIV Life Cycle Stages

Viruses cannot replicate by themselves. They can only multiply by infecting host cells. HIV enters the body in the form of particles or virions. The virions must find and attach themselves to human cells to be able to survive. They do this through a series of steps (see Figure 1):^2,4-6

1. Binding
2. Fusion
3. Reverse transcription
4. Integration
5. Replication
6. Assembly
7. Budding

First, the HIV virion attaches itself to a CD4 cell. This is called binding. Next, outer membranes of the 2 cells fuse together. This allows them to join. As a result, the HIV can now enter the CD4 cell.^2,4-6

Once inside the cell, HIV releases an enzyme. This enzyme turns HIV RNA into DNA. This process is called reverse transcription. It lets the HIV DNA enter the center of the CD4 cell. This center is called the nucleus. Here, the genetic material of both cells can combine. This step is called integration.^4-6

The virus can now use the cell’s machinery. It uses the cell's DNA to make long chains of HIV proteins. This is replication. Then, these proteins move to the edge of the cell. They combine with HIV RNA. This is called assembly. Finally, the new virus pushes out of the cell. This is budding. The new virions find new CD4 cells to attach themselves to. The process repeats. Eventually, this allows the virus to spread through the body.^4-6

When does HIV progress to AIDS?

Within a few weeks of exposure to HIV, a person will develop an acute level of infection. As the virus expands and spreads through the body, the person may have flu-like symptoms, such as headache or fever.

At this stage, the body’s immune system tries to fight the virus by producing antibodies. Antibodies are proteins the body uses to fight germs. The presence of these antibodies in the blood is how doctors can diagnose HIV infection.^1,3

When a person reaches a chronic level of infection, symptoms often disappear. But the virus is still present, and the person can still transmit the virus to others.^1,3

If a person’s CD4 count drops to below 200, doctors diagnose them with AIDS. This is the most advanced state of HIV. By now the virus has damages the immune system to the point that fighting infections is very hard.^1,3

The length of time from initial transmission to AIDS varies widely. It may take just a few years, or it may never happen. Therefore, the sooner a diagnosis is made and a person begins treatment, the more easily HIV can be controlled.^1,3

How treatment stops the HIV life cycle

A combination of special medicines, called antiretroviral therapy (ART), can control the progression and transmission of HIV. Specifically, ART blocks the various life stages of the virus and can stop it from spreading through the body. It can also reduce the risk of transmitting the virus to someone else.^1,3,4

There is no cure for AIDS or HIV. Nevertheless, ART can help people with HIV live long, healthy lives.^1,3,4