Human immunodeficiency virus, or HIV, is a virus that attacks the body’s immune system — specifically, white blood cells called CD4-positive (CD4+) T-helper cells.

Those cells, which are sometimes referred to as CD4 cells, T-helper cells, or T4 cells, play an important role in identifying pathogens that invade the body and in marshaling an immune response against them. Left untreated, HIV infiltrates and destroys CD4 cells, impairing the immune system’s ability to fight off infections and diseases.
When the number of CD4 cells drops low enough, or certain infections related to an impaired immune system occur, a person may be diagnosed with the final stage of HIV infection: acquired immunodeficiency syndrome, or AIDS.

When the immune system is weakened from AIDS, the body may have difficulty fighting off certain cancers or viral, fungal, or bacterial infections, and these conditions may prove fatal.

While there’s no cure for HIV yet, effective HIV treatment, known as antiretroviral therapy (ART), can reduce the amount of virus to undetectable levels, allow people to live longer, healthier lives, and help prevent the virus's transmission to others.

Signs and Symptoms of HIV/AIDS

There are three main stages of HIV infection, each with its own symptoms.

Stage 1: Acute HIV Infection

Within the first two to four weeks after HIV infection, about two-thirds of people will experience symptoms that feel like a really bad flu. As the immune system rallies to fight off the virus, fever may develop along with additional symptoms, such as sore throat, swollen glands, mouth sores, rashes, diarrhea, fatigue, headache, and muscle and joint pain.

This stage, called acute infection or primary HIV infection, can last for a few days, or it can stretch into weeks.

Stage 2: Clinical Latency

If the infection goes undiagnosed or untreated, the immune system can bring the HIV level down some, but it can’t completely control or contain it; the virus is still active but multiplies more slowly, often without causing any symptoms. This is also called the clinical latency stage, or chronic HIV infection, and it can last up to 15 years.

At this stage, people with HIV who aren’t taking medication still have a sufficient amount of virus in their system to transmit it to others, even if they don’t have symptoms, and the virus continues to damage the immune system over that time, leading to worsening health.

Stage 3: AIDS

If a person goes for years without treatment for HIV, the next and final stage is AIDS.

AIDS symptoms can include:
  • Sudden weight loss
  • Recurring fever
  • Night sweats
  • Fatigue and weakness
  • Swollen lymph glands
  • Chronic diarrhea
  • Sores in the mouth, anus, or genitals
  • Blotches on the skin, under the skin, or inside the mouth, nose, or eyelids
  • Neurological issues, including memory loss and depression
Some of these symptoms may be the result of a so-called opportunistic infection, such as pneumonia, which an immune system badly damaged by HIV can’t effectively fight.

Learn More About Signs and Symptoms of HIV

Causes and Risk Factors of HIV/AIDS

HIV is spread by direct contact with certain body fluids from a person with HIV who has a detectable viral load. These fluids are:

  • Blood
  • Semen (cum) and preseminal fluid
  • Rectal fluids
  • Vaginal fluids
  • Breast milk
For transmission to occur, the virus in these fluids must enter the bloodstream of an HIV-negative person through a mucous membrane (found in the rectum, vagina, mouth, or tip of the penis), through open cuts or sores, or direct injection.

In the United States, HIV is mostly spread through sex, particularly anal and vaginal intercourse. People can also transmit HIV by sharing used injection equipment, such as syringes and other paraphernalia.

Mothers can spread HIV to babies during pregnancy, birth, and breastfeeding.

HIV is a flimsy virus that can’t live for long outside the human body and can’t reproduce without a human host. That means it isn’t spread through saliva on silverware; from kisses on the cheek, hugs, sharing toilets, or closed-mouth kissing; or by mosquitoes, ticks, and other insects.
If a person is on effective antiretroviral treatment for HIV, they can lower their viral load to an undetectable level, at which point they effectively have no risk of sexually transmitting HIV to their HIV-negative partners.

Learn More About HIV Transmission

Duration of HIV

There’s currently no cure for HIV; once you get HIV, you have it for life.But HIV medicines have dramatically improved life expectancy for people with HIV, and with the right treatment and care, someone with HIV can now have a life expectancy similar to that of an HIV-negative person.
If HIV is left untreated, signs of illness can develop within 5 to 10 years and the time span from HIV transmission to a diagnosis of AIDS is about 10 to 15 years.

Treatment and Medication Options for HIV

If you test positive for HIV, research shows that if you start taking medicine immediately (or even return to treatment after some time off) and stay on it, you can bring the amount of virus in your blood (your viral load) to undetectable levels, protect your immune system, and prevent transmission to others.
Agencies such as the National Institutes of Health (NIH) recommend you start HIV treatment as soon as possible after diagnosis.

HIV Treatment Team

Talk to a healthcare provider about treatment choices and the resources that are available to you.There are no-fee or low-cost programs that ensure that everyone, no matter their income or insurance status, can receive and stay on treatment.

Medication Options

There are more than 30 different HIV drugs, divided into eight classes. Known collectively as antiretroviral therapy (ART), they prevent the virus from replicating in different ways.People typically take a combination of three drugs from at least two different classes, although new drug combinations require only two medicines, combined in one pill.
Most antiretroviral drugs need to be taken every day to work properly. Although it can be difficult to stick to this routine, it’s a must in order to keep your viral load (the amount of HIV in your body) low and avoid developing possible drug resistance.
In January 2021, the U.S. Food and Drug Administration (FDA) approved the first long-acting treatment for HIV. The once-a-month injection, administered by a healthcare provider, is a combination of cabotegravir and rilpivirine — sold under the brand name Cabenuva — and is meant for patients who have already lowered their viral load.The shots could be especially beneficial for people who struggle with a daily pill schedule.

Side Effects of Medication

All medicines have potential side effects, and HIV medicines are no different. When you first start ART, you may experience:
  • Anemia
  • Diarrhea
  • Headache
  • Fatigue
  • Nausea
  • Nerve problems
  • Rash
  • Pain
When taken long term, certain HIV medicines can be associated with serious side effects, such as high cholesterol, lipodystrophy (gain or loss of body fat), diabetes, osteoporosis, or liver damage. Ask your doctor what to expect and how to stay healthy.
According to the NIH’s Office of AIDS Research, ART is recommended for all transgender people with HIV, though some antiretroviral drugs may interact with gender-affirming hormone therapy. Be sure your doctor is aware of any other medications and supplements you’re taking and that they are monitoring you.

Learn More About Treatment for HIV

Prevention of HIV

There a number of strategies that can reduce your risk of becoming infected with HIV or greatly lower the odds that you will transmit the virus to an HIV-negative partner.

If you are using ART regularly and precisely as prescribed and have lowered your viral load to consistently undetectable levels (which usually takes up to six months, followed by ongoing care) your risk of transmitting the virus to a sexual partner is essentially zero. Research shows this method of HIV prevention is 100 percent effective in preventing sexual transmission.

You can also reduce your risk of getting or transmitting HIV if you and your partner:

  • Use HIV prevention medications, an approach called pre-exposure prophylaxis (PrEP)
  • Take a combination of HIV medicines within 72 hours after you think you may have been exposed, an approach called post-exposure prophylaxis (PEP)
  • Use condoms correctly and consistently
  • Have a circumcised penis
  • Never share drug injection equipment
  • Limit your number of sexual partners
  • Abstain from sex or choose less risky sexual behaviors, such as oral sex or mutual masturbation instead of anal or vaginal sex
  • Get checked and treated for other sexually transmitted diseases
HIV can be passed from mother to child at any point during pregnancy, but if you’re pregnant and have HIV, you can prevent this by making sure you take your HIV medicines as directed so that you have an undetectable viral load. By adhering to treatment throughout pregnancy, labor, and delivery, and if your baby takes HIV medicine four to six weeks after birth, you can lower the risk of transmission to 1 percent or less, according to the CDC.
To understand your options, consider checking out the CDC’s Risk Reduction Tool.

PrEP (Pre-Exposure Prophylaxis)

The FDA has approved two drugs to prevent HIV transmission: Truvada and Descovy. Both contain a medicine called emtricitabine combined with a version of a drug called tenofovir. Both have been found to be 99 percent effective in preventing sexual transmission of HIV when taken as prescribed by a doctor.

Studies also show that PreP medications are between 74 percent and 84 percent effective in preventing HIV transmission through the shared used of injection equipment.

RELATED: How to Talk to Your Doctor About Preventing HIV

PrEP is recommended for people at high risk of becoming infected with HIV. This includes people who have a sexual partner with HIV (especially someone with an unknown or detectable viral load), people dating someone in the first six months of HIV treatment (before they reach undetectable status), sexually active transgender people, people attempting to conceive with a partner who is living with HIV, and people who have had a sexually transmitted infection in the past year.
HIV prevention drugs are not a vaccine, and only work while you are taking them.While research has found that HIV prevention drugs taken four days a week can block HIV transmission in people engaging in condomless anal sex, no studies have assessed the medications' effectiveness in people who have vaginal sex. The FDA has approved HIV prevention medications only for use on a daily basis.
For transgender women, preliminary data suggests that PrEP medicines do not reduce the effectiveness of gender-affirming hormones.But estrogen has been found to slightly reduce the levels of PrEP drugs. It’s not yet known whether that decreases PrEP’s effectiveness. Research is ongoing.

PEP (Post Exposure Prophylaxis)

If you think you may have been exposed to HIV — for instance if a condom broke or you have experienced a sexual assault — you can also take medicine after the event to prevent yourself from acquiring HIV. If you visit a healthcare provider and begin taking the medicine within 72 hours of exposure, it can prevent any HIV in your system from setting up shop and proliferating. Often it’s emergency rooms that provide PEP.

Once you start the medicine, you will take it for 28 days, until the medicine runs out. PEP is highly effective (though not 100 percent); but the sooner it’s started, the better.

Research and Statistics: How Many People Have HIV/AIDS?

In 2019, close to 37,000 people were diagnosed with HIV in the United States, according to the latest figures available from the CDC. The annual number decreased by approximately 9 percent between 2015 and 2019.

The CDC further estimates that roughly 1.2 million people in the United States were living with HIV at the end of 2019, and that about 13 percent of those individuals were unaware they were HIV-positive.

Male-to-male sexual contact accounted for about 65 percent of new HIV diagnoses; heterosexual sexual contact, 23 percent; injection drug use, 7 percent; male-to-male sexual contact in combination with injection drug use, 4 percent.
Globally, the HIV pandemic continues, with an estimated 37.7 million people living with HIV in 2020, according to UNAIDS.

Anyone can acquire HIV, but the prevalence of HIV is not the same in all communities and varies depending on social and demographic factors.

Despite the existence of effective treatment, people still die of AIDS-defining illnesses, though it’s difficult to know how many. The CDC now identifies the number of people with HIV who died in a year, but it doesn’t separate out deaths from AIDS-defining illnesses. In 2019, 15,815 people living with HIV in the United States and dependent territories died of any cause.

Conditions Related to HIV/AIDS

People with HIV or AIDS are more likely to get several kinds of cancers. In fact, some cancers are considered AIDS-defining conditions. They include:

  • Kaposi sarcoma
  • Non-Hodgkin lymphoma
  • Cervical cancer
Some cancers are also more common in people with HIV/AIDS, though they are not considered AIDS-defining. These include:
  • Anal cancer
  • Hodgkin disease
  • Melanoma
  • Liver cancer
  • Lung cancer
  • Mouth and throat cancer
  • Testicular cancer
  • Squamous cell and basal cell skin cancers

Resources We Love

Favorite Organizations for HIV

Centers for Disease Control and Prevention (CDC)

The CDC works 24/7 to protect Americans from health, safety, and security threats. From statistics to treatment options, the agency provides comprehensive information about HIV and AIDS.


25 HIV Resources You Should Know About

This organization collaborates with departments across the federal government to offer HIV-related information. It’s a great source for up-to-date news about treatments and events.

Clinical Info

Sponsored by the National Institutes of Health’s Office of AIDS Research, this site gives you access to the latest HIV/AIDS medical practice guidelines, clinical trials, and other research material. We like their glossary feature, which allows users to search different terms related to HIV and AIDS.

Greater Than AIDS

If you’ve got questions, Greater than AIDS has answers. The organization offers accessible HIV resources with more than 100 FAQs in both English and Spanish.

Favorite Online Support and Advocacy Networks 

AIDS Healthcare Foundation (AHF)

For more than 30 years, AHF has been committed to providing cutting-edge medical care to the public, regardless of a person's ability to pay. AHF gives patients access to specialists, medication, and services.

Ryan White HIV/AIDS Program

If finances are a problem, this resource is for you. The program helps people with HIV and AIDS get medical care and other services even if they don’t have health insurance or money to pay for their healthcare. The Ryan White HIV/AIDS Program provides services to more than half a million people each year.

Foundation for AIDS Research (amfAR)

AmfAR is one of the world’s leading nonprofit organizations dedicated to the support of AIDS research, HIV prevention, treatment education, and advocacy. Since 1985, the organization has invested nearly $600 million in its programs. They host different events, and their office in Washington, DC, educates governing figures, the media, and the public about evidence-based policies that address HIV and AIDS.

American Academy of HIV Medicine’s Referral Link

Looking for an HIV specialist? The American Academy of HIV Medicine is a group dedicated to supporting HIV care providers. Their Referral Link feature provides you with the most comprehensive, up-to-date database of HIV doctors around the country.

Housing Opportunities for Persons With AIDS (HOPWA)

HOPWA is the only federal program dedicated to serving the housing needs of those living with HIV and AIDS. Under this plan, HUD makes grants to local communities, states, and nonprofits for projects that benefit low-income people with HIV and AIDS.

Center for HIV Law and Policy

Disclosing your HIV status can sometimes be socially and professionally risky. This organization provides information and resources about the law as it pertains to HIV. You can even search different laws in your state.

Favorite Apps

Clinical Info HIV/AIDS from the NIH

With three different options, Clinical Info is your go-to app source. The Glossary app lets you search for definitions of more than 700 terms. Or you can try the Drug Database app, which provides access to information about different medicines. The Guidelines app provides information about federally approved HIV/AIDS medical practice guidelines. You can download one, two, or all three.


The Life4me+ app helps establish communication between physicians and patients. It lets you organize your medication schedule and set private personalized reminders. You can also enter your tests results in the app, so you always have them on hand.

Favorite HIV Home Testing Resources 

myLAB Box

Need to take an STD test, but don’t want to leave your home? myLab Box offers kits that screen for STDs like HIV, chlamydia, gonorrhea, HPV, and more. Depending on the test, you’ll mail in a small sample of urine, a vaginal swab, or a prick of blood, and you’ll get your results in one to five days.


Testing couldn’t be any more convenient. This in-home HIV test is approved by the FDA and doesn’t require sending a sample to a lab. You can test yourself in the privacy of your own home with an oral swab. The kit gives you a result in 20 to 40 minutes.

Favorite HIV Blogs

The Body: HIV/AIDS Blog Central

Reading about others’ struggles and triumphs can help you in your journey. The Body’s network of blogs features first-person accounts from the HIV/AIDS community. The topics are diverse and designed to empower people with HIV.

Favorite Patient-Centered Annual Meetings 

International AIDS Conference

The International AIDS Conference is the world’s largest conference on HIV and AIDS. It brings together scientists, policy makers, healthcare professionals, people living with HIV, funders, the media, and the community.

Ryan White HIV/AIDS Program (RWHAP) Clinical Conference

The annual RWHAP Clinical Care Conference provides cutting-edge scientific research, care, and treatment updates for clinical decision-makers who are responsible for the day-to-day care and treatment of people living with HIV.

Favorite Information on Nutrition for HIV 

The Well Project

If you’re living with HIV, nutrition is vital for your long-term health and well-being. The Well Project, a nonprofit that focuses on women with HIV and AIDS, offers resources on how to incorporate the ideal foods for optimal health. You’ll find information on how to fight weight and muscle loss, keep your energy levels high, and minimize side effects from HIV medication.

HIV/AIDS Awareness Days

Over the years, HIV and AIDS have gone from stigmatized and little-discussed conditions to the subjects of a number of awareness campaigns, walks, runs, and fundraisers throughout the year. By participating in these activities, you help bring awareness to the experience of those living with HIV and AIDS.

Learn More About HIV/AIDS Awareness Month

Additional reporting by Deborah Shapiro.

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