What Is an Example of a Retrovirus?

Medically Reviewed by Jonathan E. Kaplan, MD on July 17, 2023
3 min read

A retrovirus is a virus that works by converting its own RNA into DNA once it is in a host cell. It then integrates this DNA into the DNA of the host cell, allowing the virus to replicate. Three retroviruses can cause illness in humans, and each one has different symptoms.

One of these retroviruses is Human Immunodeficiency Virus, or HIV. This is the virus that causes Acquired Immunodeficiency Syndrome, also known as AIDS.

The other retroviruses that affect humans are HTLV type I and HTLV type II. HTLV stands for Human T-Lymphotropic Virus. This virus causes some forms of leukemia and lymphoma.

In normal cell production, your DNA tells the cells in your body what RNA to make. The RNA then makes different proteins that have different functions in the body. Retroviruses work in the opposite way, which is where their name comes from. The prefix "retro" means backward.

Once your cells are infected with the virus, they use their RNA to instruct your cells to make DNA that tells the cells to replicate the virus. Then, once that cell divides as part of normal cell production, that DNA is in the new cell. This DNA now tells the cell to create the RNA and proteins that make up the virus.

Scientists are exploring the use of this unique function of retroviruses for gene therapy. They can "infect" someone with a retrovirus that contains RNA to fix a genetic abnormality. This will cause the cell to replicate with new, healthy DNA, potentially fixing or helping a genetic condition.

The best way to find out if you have HIV is to get tested. While most people with HIV have no symptoms, some do develop a condition known as acute HIV infection two to four weeks after becoming infected with the retrovirus. Symptoms of acute HIV infection include:

If you progress to the second stage of HIV infection — called a chronic HIV infection, asymptomatic HIV infection, or clinical latency — you may not have symptoms, but the amount of retrovirus in your body will increase.

If you don't get treatment during stages one or two, you will progress to the third stage of HIV, which is AIDS. In this stage, your immune system won't function properly and you may get more infections. People with AIDS are typically expected to live for three years.

People living with HIV can live long, healthy lives, though. Many people diagnosed with HIV between the years 2000 and 2010 are expected to live till the age of 83. Your life expectancy with HIV can be long if you received treatment soon after becoming infected and are diligent about sticking to your treatments.

HTLV type I usually doesn't cause symptoms once you are infected. Roughly 5% of those who have this retrovirus will develop Adult T-Cell Leukemia (ATL), a cancer of the white blood cells. Symptoms of ATL include: 

  • Feeling tired
  • Swollen lymph nodes
  • Excess thirst
  • Fever
  • Frequent infections and illnesses
  • Nausea and vomiting
  • Skin problems
  • Bone problems
  • Swollen or enlarged liver
  • Swollen or enlarged spleen

Around 2% of those with HTLV type I will develop HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). This is a neurological condition with symptoms that include:

You typically won’t experience symptoms when you become infected with HTLV type II. Later on, though, you may develop neurological symptoms including:

  • Erectile dysfunction
  • Problems walking
  • Sensory changes
  • Cognitive impairment
  • Incontinence
  • Loss of muscle control

Some doctors believe this condition is also associated with chronic lung infections, arthritis, asthma, skin problems. 

Most people with HTLV type II remain symptom-free for their whole lives.

Retroviruses are spread through:

  • Unprotected sexual contact
  • Exposure to infected blood
  • Exposure to infected tissue
  • During pregnancy and childbirth (from parent to child)

You can reduce your risk of contracting a retrovirus by practicing safer sex methods, like using a condom, and using safer techniques if you inject drugs.

There are now drugs you can take to reduce the risk of an HIV infection before exposure. This is called pre-exposure prophylaxis or PrEP. You can also take a course of drugs after potential exposure to reduce the risk of contracting HIV. This is called post-exposure prophylaxis or PEP.