HIV Infection

Overview

HIV (human immunodeficiency virus) is a virus that attacks the body's immune system, specifically a type of white blood cell called the CD4 cell that helps fight infection. Over time, untreated HIV weakens the immune system, making it harder for the body to fight off infections and some cancers. If untreated, HIV can progress to its most advanced stage, known as AIDS (acquired immunodeficiency syndrome).

HIV is now a manageable, lifelong condition. With effective treatment using antiretroviral therapy (ART), people with HIV can keep the virus under control, maintain a healthy immune system, and live long, healthy lives. Treatment also prevents the virus from being passed on: a person who keeps the virus undetectable in their blood cannot transmit HIV to sexual partners.

Symptoms

HIV progresses in stages, and symptoms vary:

• Early (acute) HIV: Within 2 to 4 weeks of infection, some people develop a flu-like illness with fever, sore throat, rash, swollen lymph nodes, muscle aches, and fatigue. Others have no symptoms.
• Chronic (clinical latency) stage: The virus is active but reproduces at low levels, often with few or no symptoms for years, especially with treatment.
• Advanced HIV/AIDS: Without treatment, the immune system becomes severely damaged, leading to repeated or unusual infections, persistent fevers, night sweats, significant weight loss, chronic diarrhea, and certain cancers.

Because early symptoms are nonspecific and can be absent, the only reliable way to know your status is HIV testing.

Causes

HIV is caused by the human immunodeficiency virus and spreads when certain body fluids from a person with HIV enter another person's body. These fluids include blood, semen, vaginal and rectal fluids, and breast milk. Common routes of transmission include:

• Unprotected vaginal or anal sex with a person who has HIV
• Sharing needles, syringes, or other injection equipment
• From parent to child during pregnancy, birth, or breastfeeding (now largely preventable with treatment)
• Rarely, exposure to infected blood, such as needlestick injuries in healthcare

HIV is not spread through casual contact such as hugging, shaking hands, sharing food, toilets, or by insects.

Risk Factors

Factors that increase the risk of acquiring HIV include:

• Unprotected sex, especially with multiple partners or a partner whose status is unknown
• Having another sexually transmitted infection
• Sharing needles or injection equipment
• Receiving unscreened blood or non-sterile medical procedures (rare where blood is screened)

Anyone can acquire HIV. Knowing your status, your partner's status, and using prevention methods substantially reduce the risk. Pregnant people with HIV who take treatment greatly lower the chance of passing the virus to their baby.

Diagnosis

HIV is diagnosed with blood or oral fluid tests. Testing options include:

• Antibody/antigen tests: Blood tests that detect the body's response to HIV and parts of the virus; these can detect infection within a few weeks.
• Rapid and self-tests: Quick tests using a finger-prick or oral swab, useful for convenient screening.
• Nucleic acid tests: Detect the virus itself and can identify infection earlier, used in specific situations.

Because there is a "window period" after exposure before tests turn positive, repeat testing may be advised. Routine HIV testing is recommended for adults and adolescents, and more frequent testing for those with ongoing risk. After diagnosis, tests measure the CD4 count and viral load to guide treatment.

Treatment

HIV is treated with antiretroviral therapy (ART), a combination of medicines taken every day. Key points include:

• ART stops the virus from multiplying, allowing the immune system to recover and stay healthy.
• The goal is an undetectable viral load, meaning the amount of virus in the blood is too low to measure.
• People who are undetectable on treatment cannot transmit HIV through sex ("undetectable = untransmittable").
• Treatment is recommended for everyone with HIV, started as soon as possible after diagnosis.
• Regular follow-up monitors the viral load, CD4 count, overall health, and any side effects.

With consistent treatment, most people with HIV can expect a near-normal life expectancy. Stopping or skipping medication can allow the virus to rebound and the immune system to weaken.

Prevention

HIV can be prevented with several effective strategies:

• Condoms: Using condoms correctly during sex greatly reduces the risk.
• PrEP (pre-exposure prophylaxis): Medicine taken by people without HIV who are at higher risk, which is highly effective at preventing infection.
• PEP (post-exposure prophylaxis): Emergency medicine started within 72 hours after a possible exposure to reduce the chance of infection.
• Treatment as prevention: People with HIV who are undetectable on ART do not transmit the virus sexually.
• Not sharing needles and using sterile injection equipment.
• Testing and treatment in pregnancy to prevent passing HIV to the baby.

Regular testing and knowing your status are central to prevention.

When to See a Doctor

Get an HIV test if you have had a possible exposure, are starting a new sexual relationship, are pregnant, or have ongoing risk factors. Testing is confidential and widely available, and routine screening is recommended for adults.

If you think you may have been exposed to HIV in the last 72 hours, seek care urgently to ask about post-exposure prophylaxis (PEP), which must be started quickly to be effective. If you are diagnosed with HIV, see a healthcare provider promptly to begin treatment, and seek medical care for new fevers, persistent infections, or other concerning symptoms, especially if your immune system is weakened.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC).
2. World Health Organization (WHO).
3. HIV.gov, U.S. Department of Health and Human Services.