Human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency syndrome (AIDS). HIV is transmitted via blood, semen, and vaginal fluids and causes a range of symptoms that present soon after infection, including fever and mouth ulcers. After a latent period—during which HIV progresses to AIDS (HIV/AIDS), the virus's third and final stage—those infected are faced with more serious concerns, including extreme weight loss and opportunistic infections.


Watch Now: Understanding HIV and AIDS

When AIDS first appeared in 1981, most cases were fatal. Once researchers determined that HIV was the cause of AIDS and how the virus spreads, they were able to develop ways to test for the virus and develop effective treatments for preventing it from replicating in the body—a protocol called antiretroviral therapy (ART).

Now, many people who are HIV-positive and begin taking medication can go on to live otherwise long and healthy lives.

HIV/AIDS By the Numbers

  • HIV-related deaths since virus identified (worldwide): Over 30 million
  • People living with HIV today (worldwide): More than 35 million, 69% of whom are in sub-Saharan Africa
  • People in the U.S. infected with HIV: Approximately 1.2 million
  • Infected people in the U.S. who are undiagnosed (estimated): 20% to 25%

AIDS is still regarded as a rare disease in the United States: Fewer than 200,000 people who are HIV-positive go on the develop AIDS.

HIV/AIDS Symptoms

The symptoms of HIV/AIDS can be roughly divided into two categories: symptoms that appear when the body is first infected (stage 1, the acute phase), and those that may occur after years if the virus isn't treated and the infection is allowed to progress to AIDS (HIV stage 3).

Stage 2—chronic HIV infection—is typically asymptomatic. With treatment, an HIV-positive person may stay in this phase for decades. Without treatment, the virus will typically advance in eight to 12 years.

Initial Infection

Within a few weeks of entering the body, HIV triggers flu-like symptoms and, in some cases, a few other tell-tale symptoms:

  • Fever
  • Chills
  • Headache
  • Night sweats
  • Pharyngitis (sore throat)
  • Myalgia (muscle aches and pains)
  • Arthralgia (joint pain)
  • Fatigue
  • Lymphadenopathy (swollen lymph nodes, mainly on the neck)
  • Mouth ulcers

Some people also will experience nausea, diarrhea, or vomiting, and one in five will develop an "HIV rash," a maculopapular skin condition characterized by raised, pink/red areas covered with small, pimple-like bumps that often merge together into one. 


After the latent period, signs that the virus is beginning to overcome the immune system include:

  • Swollen lymph glands
  • Candidiasis (thrush), a fungal infection that usually affects the mouth
  • Skin problems: Blotches, lesions, and sores
  • Night sweats (sleep hyperhidrosis)
  • Extreme weight loss (HIV wasting)

This is also the point at which a person may become ill with opportunistic infections, so-called because they're caused by pathogens that a healthy immune system would usually be able to easily fend off. Shingles and pneumonia are two of the most common ones.


The virus that causes HIV/AIDS is classified by scientists as a retrovirus. In most living organisms, a cell's genetic material is encoded from DNA to RNA. A retrovirus is unique in that it uses its RNA coding to produce DNA within an infected cell, a reversal of the normal process.

When this occurs, the newly produced DNA is inserted into the host cell's nucleus, effectively hijacking its genetic machinery in order to create multiple copies of itself, each of which are capable of infecting and killing a multitude of other host cells. In this case, the host cells are white blood cells called "helper" T-cells—in particular, CD4 T-cells that trigger the body's immune response.

By systematically depleting these cells, HIV diminishes the body's ability to identify and neutralize the invading virus, as well as a host of other agents (viral, bacterial, parasitic) it could otherwise defend itself against.

During the initial infection, HIV replicates vigorously, infecting and destroying a substantial number of CD4 T-cells. Once it becomes latent, the virus continues to replicate silently.

In addition to HIV, a subset of the virus called provirus embeds in cells and tissues called latent reservoirs, where they can't easily be detected by the immune system. Even if HIV is brought under control with antiretroviral drugs, these proviruses can persist, ready to re-emerge as fully formed HIV the moment that treatment fails or the immune system collapses.

How HIV Spreads

HIV is spread in the following ways:

HIV cannot be transmitted through sweat, tears, saliva, feces, or urine.

Why Testing Is So Important

It is often only when an opportunistic infection first appears that a person may suspect that he or she is infected with HIV. By this time, the immune system is usually impaired, sometimes severely so. The best way to prevent this from happening is to have an HIV test at least once; people who are at high risk of HIV should be tested as often as two to four times a year.


The prognosis of HIV/AIDS was once, for many, a strong deterrent to testing. But testing positive for HIV is no longer a death sentence in developed parts of the world: Studies published in 2014 found that patients who begin ART while the amount of virus in their bodies is relatively low have the same life expectancy of the general population.

There are five ways to test for the presence of the human immunodeficiency virus:

  • Standard point-of-care test, in which a sample of blood is taken in a doctor's office or clinic and examined for the presence of antibodies to HIV; results are returned in five to 10 days
  • Rapid point-of-care test, which can yield a result in 20 minutes by measuring both antigens (proteins on the surface of the virus) and antibodies in a sample of blood taken from a finger prick, a sample of saliva swabbed from the gums, or a urine sample
  • Nucleic acid test: A blood test that measures HIV RNA in blood and is reserved for people who are at high risk of exposure
  • At-home tests that use a sample of saliva and deliver results in about 20 minutes
  • Home collection kits that detect antibodies in a sample of blood that you collect yourself and mail to a lab for testing

When HIV Becomes AIDS

For someone whose HIV infection has not been controlled, AIDS is diagnosed in one of two ways:

Normal CD4 counts range on average from between 800 to 1600 cells per µL. A newly diagnosed HIV-positive person will be monitored regularly in order to keep track of any changes in their CD4 count.

If their CD4 count is > 500 and they are virally suppressed for at least two years, monitoring of CD4 counts is no longer necessary.


Managing the symptoms of HIV infection in the acute stage is usually a matter of getting plenty of rest and quality sleep, drinking lots of fluids, eating well, and taking over-the-counter (OTC) analgesics to relieve head or body aches, if necessary.

As soon as a person tests positive for HIV, however, it's vital that he or she begin antiretroviral drugs to get the virus under control and prevent it from replicating and causing serious and irreversible damage to the immune system.

No cure exists for AIDS, but strict adherence to anti-retroviral therapy (ART) can dramatically slow the disease's progress, prevent secondary infections and complications, and prolong life.

As a rule, antiretroviral therapy relies on three different drug molecules, a strategy known as highly active antiretroviral therapy (HAART). However, this standard triple-drug therapy may be replaced with two-drug therapies such as Juluca (dolutegravir + rilpivirine).

Antiretroviral drugs are organized into six classes based on the stage of the HIV life cycle they affect. As of 2019, there are 28 individual drug molecules and 13 fixed-dose combination (FDC) drugs made up of two or more molecules each. Eight of the FDCs can be used as a single-pill, once-daily therapy.


Although HIV is a highly contagious virus, there is a silver lining: The ways it can be transmitted are well understood and also highly avoidable if specific precautions are taken.

To reduce the risk of becoming infected with the virus, the Centers for Disease Control and Prevention (CDC) advises taking certain precautions: 

  • Limit the number of sexual partners you have and make sure anyone you're intimate with has been tested and is HIV-negative
  • Always use a barrier such as a condom during sexual encounters, including oral sex
  • Use new, sterile needles and syringes if you are an intravenous drug user
  • Take a daily medication to help protect yourself from infection, which is known as pre-exposure prophylaxis (PrEP)


HIV infection is a chronic disease, which means it is something that must be dealt with on a daily basis. The most obvious aspects of coping with being HIV-positive include doing all that's necessary to stay healthy: Living a healthy lifestyle that will support the health of the immune system; being compliant with medication; and following doctor's orders regarding regular check-ups to keep track of any changes in viral load and overall health.

However, the stigma that persists regarding HIV and continued misunderstandings about how it is transmitted means that coping extends to how you conduct yourself around others and also how you might feel about yourself. For this reason, being upfront with trusted friends and family members about your HIV status can go a long way toward helping you to feel supported and cared for.

Equally important, finding a community of others who also are HIV-positive can be an important lifeline and source of advice for dealing with all aspects of being HIV-positive. You can get such support by attending local support groups for people with your diagnosis and/or by joining online versions. If you're having trouble finding one, there are multiple resources you can turn to.

A Word From Verywell

While receiving an HIV diagnosis can be upsetting, today's treatments and improved understanding of the disease have made it a manageable, chronic illness for many people. If you have HIV, it is important to work with your doctor, who can advise you on what you need to do to stay healthy.

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