Human Immunodeficiency Virus HIV

Human Immunodeficiency Virus(HIV) is a virus spread through body fluids that affects specific cells of the immune system, called CD4 cells, or T cells. Over time, HIV can destroy so many of these cells that the body can’t fight off infections and disease. When this happens, HIV infection leads to AIDS. Learn more about the stages of HIV and how to tell whether you’re infected. See Video Transmission and Prevention of HIV  

What is HIV? 

HIV stands for human immunodeficiency virus. It is the virus that can lead to acquired immunodeficiency syndrome, or AIDS. Unlike some other viruses, the human body cannot get rid of HIV. That means that once you have HIV, you have it for life.

No safe and effective cure currently exists, but scientists are working hard to find one, and remain hopeful. Meanwhile, with proper medical care, HIV can be controlled. Treatment for HIV is often called antiretroviral therapy or ART. It can dramatically prolong the lives of many people infected with HIV and lower their chance of infecting others. Before the introduction of ART in the mid-1990s, people with HIV could progress to AIDS in just a few years. Today, someone diagnosed with HIV and treated before the disease is far advanced can have a nearly normal life expectancy.

HIV affects specific cells of the immune system, called CD4 cells, or T cells. Over time, HIV can destroy so many of these cells that the body can’t fight off infections and disease. When this happens, HIV infection leads to AIDS.

Where did HIV come from?

Scientists identified a type of chimpanzee in West Africa as the source of HIV infection in humans. They believe that the chimpanzee version of the immunodeficiency virus (called simian immunodeficiency virus, or SIV) most likely was transmitted to humans and mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood. Studies show that HIV may have jumped from apes to humans as far back as the late 1800s. Over decades, the virus slowly spread across Africa and later into other parts of the world. We know that the virus has existed in the United States since at least the mid- to late 1970s.

What are the stages of HIV?

HIV disease has a well-documented progression. Untreated, HIV is almost universally fatal because it eventually overwhelms the immune system—resulting in acquired immunodeficiency syndrome (AIDS). HIV treatment helps people at all stages of the disease, and treatment can slow or prevent progression from one stage to the next.

A person can transmit HIV to others during any of these stages:

Acute infection: Within 2 to 4 weeks after infection with HIV, you may feel sick with flu-like symptoms. This is called acute retroviral syndrome (ARS) or primary HIV infection, and it’s the body’s natural response to the HIV infection. (Not everyone develops ARS, however—and some people may have no symptoms.)

During this period of infection, large amounts of HIV are being produced in your body. The virus uses important immune system cells called CD4 cells to make copies of itself and destroys these cells in the process. Because of this, the CD4 count can fall quickly.

Your ability to spread HIV is highest during this stage because the amount of virus in the blood is very high.

Eventually, your immune response will begin to bring the amount of virus in your body back down to a stable level. At this point, your CD4 count will then begin to increase, but it may not return to pre-infection levels.

Clinical latency (inactivity or dormancy): This period is sometimes called asymptomatic HIV infection or chronic HIV infection. During this phase, HIV is still active, but reproduces at very low levels. You may not have any symptoms or get sick during this time. People who are on antiretroviral therapy (ART) may live with clinical latency for several decades. For people who are not on ART, this period can last up to a decade, but some may progress through this phase faster. It is important to remember that you are still able to transmit HIV to others during this phase even if you are treated with ART, although ART greatly reduces the risk. Toward the middle and end of this period, your viral load begins to rise and your CD4 cell count begins to drop. As this happens, you may begin to have symptoms of HIV infection as your immune system becomes too weak to protect you .

AIDS (acquired immunodeficiency syndrome): This is the stage of infection that occurs when your immune system is badly damaged and you become vulnerable to infections and infection-related cancers called opportunistic illnesses. When the number of your CD4 cells falls below 200 cells per cubic millimeter of blood (200 cells/mm3), you are considered to have progressed to AIDS. (Normal CD4 counts are between 500 and 1,600 cells/mm3.) You can also be diagnosed with AIDS if you develop one or more opportunistic illnesses, regardless of your CD4 count. Without treatment, people who are diagnosed with AIDS typically survive about 3 years. Once someone has a dangerous opportunistic illness, life expectancy without treatment falls to about 1 year. People with AIDS need medical treatment to prevent death.

How can I tell if I’m infected with HIV?

The only way to know if you are infected with HIV is to be tested. You cannot rely on symptoms to know whether you have HIV. Many people who are infected with HIV do not have any symptoms at all for 10 years or more. Some people who are infected with HIV report having flu-like symptoms (often described as “the worst flu ever”) 2 to 4 weeks after exposure. Symptoms can include:

• Fever

• Enlarged lymph nodes

• Sore throat

• Rash

• Visit National HIV and STD Testing Resources and enter your ZIP code.

• Text your ZIP code to KNOWIT (566948), and you will receive a text back with a testing site near you.

• Call 800-CDC-INFO (800-232-4636) to ask for free testing sites in your area.

These symptoms can last anywhere from a few days to several weeks. During this time, HIV infection may not show up on an HIV test, but people who have it are highly infectious and can spread the infection to others.

However, you should not assume you have HIV if you have any of these symptoms. Each of these symptoms can be caused by other illnesses. Again, the only way to determine whether you are infected is to be tested for HIV infection. For information on where to find an HIV testing site,

These resources are confidential. You can also ask your health care provider to give you an HIV test.

Two types of home testing kits are available in most drugstores or pharmacies: one involves pricking your finger for a blood sample, sending the sample to a laboratory, then phoning in for results. The other involves getting a swab of fluid from your mouth, using the kit to test it, and reading the results in 20 minutes. Confidential counseling and referrals for treatment are available with both kinds of home tests.

If you test positive for HIV, you should see your doctor as soon as possible to begin treatment.

Is there a cure for HIV?

For most people, the answer is no. Most reports of a cure involve HIV-infected people who needed treatment for a cancer that would have killed them otherwise. But these treatments are very risky, even life-threatening, and are used only when the HIV-infected people would have died without them. Antiretroviral therapy (ART), however, can dramatically prolong the lives of many people infected with HIV and lower their chance of infecting others. It is important that people get tested for HIV and know that they are infected early so that medical care and treatment have the greatest effect.
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