HIV (Human Immunodeficiency Virus) Infection

How HIV affects the body

HIV targets CD4 T cells. It inserts its genetic material into the cell's DNA and uses the cell to make new viruses, killing it in the process. A healthy adult has roughly 500 to 1,500 CD4 cells per microliter of blood. Untreated HIV lowers this count by an average of about 50 to 100 a year. When it falls below 200, or certain infections or cancers appear, the stage is called AIDS (acquired immunodeficiency syndrome).

Antiretroviral therapy stops the virus from copying itself. The viral load falls, usually to undetectable levels within 6 months, and CD4 cells recover.

Stages of HIV infection

Symptoms

Early (acute) HIV symptoms

About 2 in 3 people develop an illness 2 to 4 weeks after infection, often mistaken for flu or mono. See acute HIV infection for details. Symptoms last 1 to 2 weeks and may include:

• fever and night sweats
• sore throat and painful mouth ulcers
• a flat or raised red rash on the trunk
• swollen lymph nodes
• muscle and joint aches, headache, tiredness
• diarrhea

Many people have no symptoms at all, which is why testing matters.

Chronic HIV

Most people feel well for years. Some have persistent swollen glands, recurrent shingles, oral thrush, or skin problems such as seborrheic dermatitis.

Advanced HIV and AIDS

• unexplained weight loss and chronic diarrhea
• persistent fever and night sweats
• opportunistic infections: Pneumocystis pneumonia, tuberculosis, esophageal candidiasis, cryptococcal meningitis, toxoplasmosis, cytomegalovirus
• cancers: Kaposi sarcoma, lymphoma, cervical and anal cancer
• memory and thinking problems

How HIV is transmitted

HIV spreads only through specific body fluids from someone with a detectable viral load: blood, semen and pre-seminal fluid, vaginal and rectal fluids, and breast milk.

Main routes:

• Anal sex: the highest sexual risk, especially for the receptive partner
• Vaginal sex
• Sharing needles and injection equipment
• Pregnancy, birth and breastfeeding, now rare with treatment
• Needlestick injuries in healthcare (low risk)

HIV is not spread by kissing, hugging, sharing cups, toilets, swimming pools, mosquitoes, sweat or tears. Oral sex carries a very low risk.

Having another sexually transmitted infection such as syphilis or herpes raises the risk of getting or passing HIV.

Testing for HIV

The CDC recommends that everyone aged 13 to 64 be tested at least once, and people with ongoing risk at least yearly.

A negative test inside the window period should be repeated. A positive screening test is always confirmed with further testing.

After diagnosis, baseline tests include CD4 count, viral load, resistance testing, kidney and liver function, hepatitis B and C, tuberculosis and other STI screening.

Treatment

Antiretroviral therapy (ART) is recommended for everyone with HIV, started as soon as possible after diagnosis, often the same day.

• Modern ART is usually a combination of 2 or 3 drugs, often in a single daily pill. Common regimens are built on an integrase inhibitor such as bictegravir or dolutegravir.
• Long-acting injections (cabotegravir with rilpivirine) every 1 to 2 months are an option for people who are already virally suppressed.
• Viral load is checked regularly; the goal is an undetectable level (usually below 50 copies/mL).
• Missed doses can allow drug resistance, so taking ART consistently matters.

People with low CD4 counts also take preventive antibiotics against opportunistic infections until immunity recovers.

Undetectable = Untransmittable (U=U)

People with HIV who take ART and maintain an undetectable viral load for at least 6 months do not transmit HIV through sex. This is supported by large studies of thousands of couples.

Prevention

• Condoms, used correctly every time
• PrEP (pre-exposure prophylaxis): daily pills or long-acting injections taken by HIV-negative people, highly effective when used as prescribed
• PEP (post-exposure prophylaxis): a 28-day course of ART started within 72 hours of a possible exposure, the sooner the better
• Treatment as prevention: partners with an undetectable viral load
• Never sharing needles; using syringe services programs
• Testing and treatment in pregnancy, which lowers transmission to the baby to under 1%

Living with HIV

With treatment, HIV is a manageable long-term condition. People with HIV work, have relationships and children, and age with HIV. Long-term care focuses on taking ART consistently, regular blood tests, vaccinations, and managing heart, bone, kidney and mental health, which can be affected by HIV and aging. Stopping smoking is one of the biggest health gains for people with HIV.

Frequently asked questions

What are the first signs of HIV?

Many people develop a flu-like illness 2 to 4 weeks after infection: fever, sore throat, rash, swollen glands, muscle aches, mouth ulcers and tiredness lasting 1 to 2 weeks. Others have no symptoms. Symptoms alone cannot diagnose HIV, so testing is essential after any possible exposure.

How soon can an HIV test detect infection?

A lab antigen/antibody blood test can usually detect HIV 18 to 45 days after exposure, and a nucleic acid test 10 to 33 days after. Rapid and home antibody tests may take up to 90 days. If you test negative within the window period, test again later.

Can HIV be cured?

There is no widely available cure yet. Antiretroviral therapy controls the virus so well that it becomes undetectable, the immune system recovers, and life expectancy approaches normal. A handful of people have been cured after stem cell transplants for cancer, but this is not a treatment option for HIV alone.

What is the difference between HIV and AIDS?

HIV is the virus. AIDS is the most advanced stage of untreated HIV infection, defined by a CD4 count below 200 or certain serious infections or cancers. With early treatment, most people with HIV never develop AIDS.

What should I do after a possible HIV exposure?

Go to an ER, urgent care or sexual health clinic as soon as possible and ask about PEP (post-exposure prophylaxis). It must be started within 72 hours, ideally within hours, and taken for 28 days. You will be tested at the start and again afterward.