HIV complications happen when untreated HIV destroys enough of the immune system that infections and cancers the body would normally fend off take hold. Once the CD4 count drops below 200 cells/mm³, or an opportunistic infection appears, HIV has progressed to AIDS CDC. With treatment started early, most of these complications never develop.
in 2023
≈723,000 — U=U
| Item | Value |
|---|---|
| New diagnoses | 38,800 — in 2023 |
| Living with HIV | 1.12 million |
| Virally suppressed | ~65% — ≈723,000 — U=U |
| On PrEP | 381,000 |
The essentials: how HIV damages the immune system
HIV is a virus that attacks the body's immune system, specifically the CD4 T-cells that coordinate your defenses. The infection moves through three stages. The acute stage comes within weeks of exposure, when the viral load is enormous and the person is very contagious. The chronic stage, also called clinical latency, can last a decade or more untreated, with the virus staying active while symptoms are often absent. The final stage is AIDS, defined by a CD4 count under 200 cells/mm³ or the arrival of an opportunistic infection.
The CD4 count is the key to risk-staging. As it falls, the menu of infections you're vulnerable to widens. "HIV complications" means what your immune system can no longer hold back, and a number on a lab report predicts danger long before you feel anything. About 1.12 million people are living with HIV in the US, and roughly two-thirds are virally suppressed CDC AtlasPlus, 2023. Suppression keeps complications away.
HIV is not curable, but it is manageable. Once people get HIV they have it for life. Yet a 20-year-old who starts treatment before their CD4 count falls below 200 now has a life expectancy approaching that of the general population Lancet HIV. The complications below describe HIV left untreated, not HIV in someone on therapy.
Symptoms and complications, stage by stage
Acute HIV symptoms
Within 2 to 4 weeks after infection, about 90% of people develop flu-like illness, called acute retroviral syndrome hiv.gov. Fever, chills, rash, night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes, and mouth ulcers are common, but some people have none at all. These symptoms look exactly like the flu and can neither confirm nor rule out HIV. This window is also when the viral load peaks above a million copies/mL and onward transmission risk is highest, so flu-like symptoms after a real risk are worth an urgent test rather than a wait-and-see.
The silent years
After the acute phase, many people feel completely well for years during clinical latency. The virus keeps replicating and quietly chipping away at CD4 cells, but nothing on the outside signals it. This is the most dangerous part of HIV's natural history because it feels like nothing is wrong. Testing is the only reliable way to know your status.
AIDS-stage opportunistic infections and cancers
When CD4 cells fall low enough, opportunistic infections move in: organisms that a healthy immune system shrugs off but that become serious or fatal in advanced HIV StatPearls. The risk for specific infections tracks with how low the CD4 count has fallen:
- Pneumocystis pneumonia (PCP) — a fungal lung infection causing dry cough, breathlessness, and fever; one of the classic AIDS-defining illnesses as CD4 drops toward and below 200.
- Oral and esophageal candidiasis (thrush) — a yeast overgrowth that coats the mouth or throat with white plaques and makes swallowing painful; it often signals failing immunity.
- Kaposi sarcoma — a cancer driven by a herpesvirus that produces purple or dark skin and mouth lesions and can involve internal organs.
- Cytomegalovirus (CMV) — a virus that, at very low CD4 counts, attacks the retina (threatening blindness) or the gut.
- Toxoplasmosis — a parasite that can inflame the brain, causing headaches, confusion, and seizures.
- Cryptococcal meningitis — a fungal infection of the lining of the brain producing severe headache, fever, and stiff neck.
- Disseminated MAC — Mycobacterium avium complex spreading body-wide at the lowest CD4 levels, causing fevers, weight loss, and night sweats.
- Tuberculosis (TB) — which is more aggressive and more likely to spread beyond the lungs in people with HIV.
These are not things to self-diagnose. They're the reason early diagnosis and treatment exist, since almost all of them are preventable when therapy keeps the immune system intact.
Testing: confirming HIV and staging risk
Testing is the only way to know your status. A finger-stick or oral-swab rapid test gives results in minutes, or a lab draws blood, and testing is free at many health departments CDC. At-home kits exist too; you can read about doing an hiv self-testing at home before you decide which route fits you.
The most common testing mistake is testing too early and trusting a negative. Each test type has a window:
| Test type | Detection window after exposure | Sample |
|---|---|---|
| Nucleic-acid test (NAT) | 10–33 days | Blood draw |
| Antigen/antibody (4th-gen) lab test | 18–45 days | Blood draw |
| Antibody / rapid / self-test | 23–90 days | Finger-stick or oral swab |
A negative result is conclusive only after the window has fully passed with no new exposure during it. If you're unsure where you sit on that timeline, our guide on when to test after exposure walks through it. When you're ready, you can get tested. After diagnosis, clinicians stage your immune health with a CD4 count and measure your viral load to guide treatment.
Treatment: stopping complications before they start
Everyone with HIV should take HIV treatment (ART) and start as soon as possible after diagnosis CDC. ART is a combination of HIV medicines, with single-pill and multi-pill options drawing on integrase inhibitors, NRTIs, NNRTIs, and protease inhibitors. The goal is an undetectable viral load, and most people reach it within the first several months of starting.
Treatment is what prevents the complications above. By suppressing the virus, ART lets the CD4 count recover and climb back out of the danger zone, so the opportunistic infections never get their opening. Treatment is lifelong, and an undetectable viral load means control rather than a cure. Latent HIV reservoirs persist in cells and tissues, and the virus rebounds if treatment stops HHS clinicalinfo. A few people have reached long-term remission after high-risk stem-cell transplants done for cancer, using rare HIV-resistant donor cells NIH, 2022, but those are not a scalable or available cure. The practical and emotional side of starting treatment and building a routine is covered in coping with hiv/aids.
Prevention: avoiding HIV and its complications
The CDC's core prevention tools are condoms, PrEP, PEP, treatment-as-prevention (U=U), and regular testing CDC. U=U means a person on treatment who stays virally suppressed will not transmit HIV to sex partners. Across the PARTNER studies, mixed-status couples logged tens of thousands of condomless sex acts with zero linked transmissions while the positive partner was undetectable PARTNER, Lancet.
For people without HIV, PrEP cuts the risk of getting HIV from sex by about 99% when taken as prescribed CDC PrEP. Daily oral options are Truvada and Descovy, and there's a long-acting injectable, cabotegravir. Newer twice-yearly injectable lenacapavir produced zero infections among women in the PURPOSE 1 trial WHO. PrEP requires a confirmed HIV-negative test before starting and at follow-ups.
If you think you've just been exposed, that's an emergency. PEP is a 28-day course started within 72 hours that can stop infection from taking hold, and the sooner you start the better CDC PEP. This is an urgent-care or ER conversation, not a wait-and-test one. Read about pep for hiv so you know what to ask for. Perinatal transmission is also preventable: with ART during pregnancy and labor plus newborn prophylaxis, the risk to the baby can be reduced to less than 1%.
When to see a clinician
Get same-day care if you may have been exposed within the last 72 hours, because that's the PEP window and waiting closes it. See a clinician promptly if you've had a real risk and develop flu-like symptoms a few weeks later, since that's when acute HIV is most contagious. If you already have HIV and develop a persistent cough, breathlessness, painful swallowing, severe headache with fever or stiff neck, new skin lesions, vision changes, or unexplained weight loss and fevers, treat it as urgent, since those can be signs of opportunistic infection. And if you're sexually active or share injection equipment, make routine testing part of your care even when you feel fine.