HIV Overview

What is HIV and AIDS?

HIV stands for human immunodeficiency virus, which is the virus that causes HIV infection. The abbreviation “HIV” can refer to the virus or to HIV infection. 

AIDS stands for acquired immunodeficiency syndrome. AIDS is the most advanced stage of HIV infection.

HIV attacks and destroys the infection-fighting CD4 cells (CD4 T lymphocytes) of the immune system. The loss of CD4 cells makes it difficult for the body to fight off infections, illnesses, and certain cancers.

Without treatment, HIV can gradually destroy the immune system, causing health decline and the onset of AIDS. This includes an increased likelihood of getting other infections like hepatitis, tuberculosis, and some sexually transmitted infections. 

With treatment, the body can prevent HIV from destroying CD4 cells, and the immune system can recover. A healthy immune system protects against other infections.

See the The Stages of HIV Infection fact sheet for a more complete overview of how HIV progresses to AIDS.

How is HIV transmitted?

HIV can be transmitted through bodily fluids, including blood, semen (“cum”), pre-seminal fluid (“pre-cum”), vaginal fluids, rectal fluids, and breastmilk. HIV can be transmitted through these fluids in the following ways—

Blood:

• Sharing needles or syringes for injecting drugs or tattooing
• Being exposed to HIV-positive blood through accidental needle sticks
• Sharing personal items that may have blood (such as razors or toothbrushes)
• Being exposed through placental exchange during pregnancy
• Eating pre-chewed foods (in case of open sores or bleeding gums)

Semen, Pre-Seminal Fluid, Vaginal Fluids, and Rectal Fluids:

• Having vaginal or anal sex
• Having oral sex (less likely, but can occur in rare cases)
• Being exposed to vaginal fluids during childbirth

Breast Milk:

• Breastfeeding

When an infant gets HIV during pregnancy, childbirth, or breastfeeding, it is called perinatal transmission of HIV. For more information on perinatal transmission, read the HIVinfo fact sheet on Preventing Perinatal Transmission of HIV.

You cannot get HIV by shaking hands or hugging a person who has HIV. You also cannot get HIV from contact with objects, such as dishes, toilet seats, or doorknobs, used by a person with HIV. HIV is not spread through the air or water or by mosquitoes, ticks, or other insects. 

Use the HIVinfo You Can Safely Share…With Someone With HIV infographic to spread this message.

What is the treatment for HIV?

Antiretroviral therapy (ART) is the use of HIV medicines to treat HIV infection. People on ART take a combination of HIV medicines (called an HIV treatment regimen) every day (pills) or by schedule (injections). 

In many cases, oral medicines may be combined into a single pill or capsule instead of multiple pills. There are newer long-acting medicines given by injection every two weeks to six months that may be appropriate for some people with HIV. 

Although injectable HIV medicines are taken less often, they require an appointment to be administered by a health care provider. See the Long-Acting HIV Medicines fact sheet for more information on injectable HIV medicines.

ART is recommended for everyone who has HIV. ART prevents HIV from multiplying, which reduces the amount of HIV in the body (called the viral load). Having less HIV in the body protects the immune system and prevents HIV from advancing to AIDS. ART cannot cure HIV, but HIV medicines can help people with HIV live long, healthy lives.

How can a person reduce the chances of transmitting HIV?

ART reduces the chances of HIV transmission. ART can reduce a person’s viral load to an undetectable level. An undetectable viral load means that the level of HIV in the blood is too low to be detected by a viral load test. People with HIV who maintain an undetectable viral load have no risk of transmitting HIV to their partners through sex.

HIV medicines taken during pregnancy, childbirth, and breastfeeding can also reduce the likelihood of perinatal HIV transmission. Evidence suggests that the odds of perinatal transmission are less than one percent when someone breastfeeds with an undetectable viral load.  

Feeding infants using properly prepared formula or pasteurized human donor milk from a milk bank can completely eliminate the chances of perinatal HIV transmission. Health care providers can help determine the best approach to infant feeding based on the likelihood that an infant will be exposed to HIV after pregnancy.

How can a person reduce the risk of getting HIV?

There are several ways to reduce the risk of getting HIV. Using condoms correctly with every sexual encounter can reduce the risk of getting HIV, particularly with partners who have HIV with a detectable viral load or whose HIV status is unknown. 

Other behaviors, like avoiding sharing needles and choosing safer sex practices (such as limiting the number of sexual partners), can also reduce the likelihood of HIV transmission.

People who do not have HIV should talk to their health care provider about pre-exposure prophylaxis (PrEP) if they believe they are at risk of getting HIV. PrEP involves taking a specific HIV medicine on a routine schedule—daily for pills or every two months for injections—before an HIV exposure. For more information, read the HIVinfo fact sheet on Pre-Exposure Prophylaxis (PrEP).

Post-exposure prophylaxis (PEP) can also reduce the chances of getting HIV. Unlike PrEP, however, PEP is taken within three days (72 hours) after an exposure. Read the HIVinfo fact sheet on Post-Exposure Prophylaxis (PEP) for more information.

What are the symptoms of HIV and AIDS?

Within two to four weeks after infection with HIV (known as early or acute HIV infection), some people may have flu-like symptoms (such as fever or chills). The symptoms may last for a few days to several weeks.

Other possible symptoms of HIV include night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes, headache, diarrhea, mouth ulcers, and skin rash. Having these symptoms does not mean you have HIV. Other illnesses can cause the same symptoms.

Some people may not feel sick during early HIV infection. During this earliest stage of HIV infection, the virus multiplies rapidly. After the initial stage of infection, HIV continues to multiply but at lower levels. 

When people are untreated, more severe HIV symptoms may appear years later, as HIV develops into AIDS. People with AIDS have weakened immune systems that make them prone to opportunistic infections. 

Opportunistic infections are infections and infection-related cancers that occur more frequently or are more severe in people with weakened immune systems than in people with healthy immune systems. See the What is an Opportunistic Infection? fact sheet to learn more.

Without treatment, HIV transmission is possible at any stage of HIV infection—even if a person with HIV has no symptoms of HIV.

How is AIDS diagnosed?

Symptoms such as fever, weakness, and weight loss may be a sign that a person’s HIV has advanced to AIDS. However, an AIDS diagnosis is based on the following criteria:

• A drop in CD4 count to less than 200 cells/mm³
  OR
• The presence of certain opportunistic infections (known as AIDS-defining conditions)

Although an AIDS diagnosis indicates severe damage to the immune system, HIV medicines can still help people at this stage of HIV infection.

This fact sheet is based on information from the following sources:

From the Centers for Disease Control and Prevention:

• About HIV
• AIDS and Opportunistic Infections

From the NIH Office of AIDS Research:

• Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection:
  • Introduction
• Recommendations for the Use of Antiretroviral Drugs During Pregnancy and Interventions to Reduce Perinatal HIV Transmission in the United States
  • Preventing HIV Transmission During Infant Feeding

From the National Institute of Allergy and Infectious Diseases (NIAID):

• HIV/AIDS

Also see the HIV Source collection of HIV links and resources.