Overview
HIV is a virus that attacks the CD4 white blood cells the body uses to fight infection. Without treatment the immune system weakens over years until serious infections and cancers take hold, and that advanced stage is called AIDS.
Treatment has changed what this diagnosis means. Antiretroviral therapy does not remove the virus, but taken every day it stops the virus multiplying, lets the immune system recover, and allows people to live long and healthy lives.
Disease Summary
- Category
- Infectious Disease
- Cause
- Human immunodeficiency virus (HIV)
- Transmission
- Blood, sexual fluids and breast milk
- Body System
- Immune System
- Preventable
- Yes
- Curable
- No
Symptoms
Common Symptoms
Many people have no symptoms at all for years. When symptoms do appear, they usually follow one of the two patterns below.
Early Flu-Like Illness
CDC reports that many people develop flu-like symptoms 2 to 4 weeks after infection, at the point when the amount of virus in the blood is highest.
Fever and Sore Throat
WHO lists fever and sore throat among the symptoms of the early phase of infection.
Headache
Headache is listed by WHO among early symptoms and is easily mistaken for malaria or influenza.
Rash
A rash may appear during the early illness and settles without specific treatment.
Swollen Lymph Nodes
Swelling of the glands in the neck, armpits or groin can appear as the infection progressively weakens immunity.
Unexplained Weight Loss
WHO lists weight loss among the symptoms that appear as untreated infection advances.
Persistent Cough
A cough that does not settle may be the first sign of tuberculosis, which WHO names as the commonest serious infection in untreated HIV.
Long-Lasting Diarrhoea
Diarrhoea that continues for weeks is listed by WHO among the symptoms of progressive infection.
Danger Signs
These point to advanced HIV disease or a serious opportunistic infection. Seek medical care without delay.
Cough, Night Sweats and Weight Loss
This combination suggests tuberculosis, which WHO lists among the severe illnesses that develop in untreated HIV and which needs urgent treatment.
Severe Headache with Fever or Neck Stiffness
This can indicate cryptococcal meningitis, a severe infection of advanced HIV that WHO names among the leading causes of death.
Repeated or Severe Bacterial Infections
Infections that keep returning or that become severe are a sign the immune system is no longer coping.
New Skin Lumps or Purple Patches
WHO lists Kaposi sarcoma and lymphomas among the cancers that appear in advanced HIV.
A CD4 Count Below 200
WHO defines advanced HIV disease as a CD4 count under 200 cells per cubic millimetre or a WHO stage 3 or 4 event, and treats it as a situation needing rapid action.
Diagnosis
Testing Offered to Everyone
CDC recommends that everyone aged 13 to 64 is tested at least once, and that people at ongoing risk test at least once a year. HIV is diagnosed by a test, never by symptoms.
Same-Day Rapid Testing
WHO states that HIV can be diagnosed using rapid diagnostic tests that give results the same day, and that self-tests are also available.
Checking the Window Period
A test can only detect HIV once enough time has passed. A negative result taken soon after a possible exposure does not rule out infection and the test must be repeated.
Confirming Every Reactive Result
WHO states that all reactive results must be confirmed by a trained health worker before a diagnosis is given. No one should be told they have HIV on the basis of a single rapid test.
Virological Testing for Infants
WHO states that children under 18 months cannot be diagnosed by antibody testing, because the mother’s antibodies are still present, so virological testing is provided from birth or at 6 weeks of age.
Laboratory Tests
Rapid Antigen and Antibody Test
The test used in most clinics and in self-test kits. A reactive result is presumptive and must be confirmed.
Laboratory Antigen and Antibody Immunoassay
Detects both the p24 antigen of the virus and the antibodies the body makes against it. CDC gives a detection window of 18 to 45 days after exposure.
Nucleic Acid Test for HIV RNA
Looks for the virus itself rather than the antibody response, so it detects infection soonest, from 10 to 33 days after exposure. This is the required test for infants.
CD4 Lymphocyte Count
Measures how much of the immune system remains. A count under 200 cells per cubic millimetre defines advanced HIV disease.
HIV Viral Load
Measures how much virus is in the blood. An undetectable viral load means treatment is working, and WHO states a person in that position does not pass HIV on sexually.
Treatment
Antiretroviral Therapy
The foundation of treatment. WHO states that antiretroviral therapy suppresses the virus, allowing the immune system to strengthen and regain the capacity to fight infections. CDC reports that most people get HIV under control within six months.
Long-Acting Injectable Therapy
An alternative for people already stable on treatment. CDC states it requires an undetectable viral load for at least three months and no history of treatment failure.
Treatment of Opportunistic Infections
Advanced HIV disease is treated alongside the HIV itself. WHO names tuberculosis, cryptococcal meningitis and severe bacterial infections as the illnesses to look for and treat.
Post-Exposure Prophylaxis
Medicine taken after a possible exposure to stop infection taking hold. CDC states it must be started within 72 hours and is for emergency situations only.
Treatment in Pregnancy and Breastfeeding
WHO states that pregnant women with HIV should start antiretroviral therapy as soon as possible, which protects the mother and helps prevent transmission to the baby.
Prevention
Use condoms consistently
WHO lists male and female condoms among the core prevention measures for HIV and other sexually transmitted infections.
Consider pre-exposure prophylaxis
WHO names oral tenofovir-based pills, the dapivirine vaginal ring, and long-acting injectable cabotegravir and lenacapavir as options for people at substantial risk.
Know your status and test regularly
Testing is the entry point to both treatment and prevention, and CDC advises at least annual testing for people at ongoing risk.
Never share needles or injecting equipment
WHO lists harm reduction services for people who inject drugs among the measures that interrupt transmission.
Treatment as prevention
WHO states that a person on antiretroviral therapy with no detectable virus in the blood will not pass HIV to their sexual partners.
Antenatal testing and treatment
Testing in pregnancy and starting treatment early prevents transmission to the baby before birth, during delivery and through breast milk.
Risk Factors
Higher Chance of Acquiring HIV
Exposure through sex, blood or injecting equipment raises the chance of infection.
- Sex without a condom with a partner whose status is unknown
- Sharing needles, syringes or other injecting equipment
- Having another untreated sexually transmitted infection
- Unsafe injections or unsterile cutting and piercing procedures
Populations Carrying the Greatest Burden
WHO and CDC identify groups where infection rates are highest and services are often hardest to reach.
- Women and girls in the WHO African Region, where 64% of people with HIV live
- Men who have sex with men
- People who inject drugs
- Sex workers and their clients
Higher Chance of Severe Illness
These groups are more likely to progress to advanced HIV disease.
- People who are diagnosed late or who are not on treatment
- Anyone with a CD4 count under 200 cells per cubic millimetre
- All children under five years living with HIV, whom WHO classes as having advanced disease regardless of their test results
- People who have interrupted treatment
Complications
Tuberculosis
WHO lists tuberculosis among the severe illnesses that untreated HIV allows to develop, and it remains the leading cause of death in people living with HIV.
Cryptococcal Meningitis
A fungal infection of the lining of the brain that WHO names as a severe opportunistic infection of advanced HIV.
Severe Bacterial Infections
Chest, blood and other bacterial infections become more frequent and more severe as immunity falls.
Kaposi Sarcoma
A cancer that causes purple or dark patches on the skin and in the mouth, listed by WHO among the cancers of advanced HIV.
Lymphoma
Cancers of the lymph system are listed by WHO among advanced-disease presentations.
Progression to AIDS
CDC states that delaying treatment allows HIV to keep damaging the immune system and raises the chance of developing AIDS.
When to Seek Medical Care
Within 72 Hours of a Possible Exposure
CDC states that post-exposure prophylaxis must begin within 72 hours, so this is a same-day matter rather than something to think over.
After Any Reactive Test Result
A reactive rapid test or self-test needs confirmatory testing by a health worker.
A Cough Lasting More Than Two Weeks
Persistent cough, night sweats or weight loss in a person living with HIV should be assessed for tuberculosis without delay.
Severe Headache, Confusion or Neck Stiffness
These may indicate meningitis and are an emergency.
During Pregnancy
WHO states that pregnant women living with HIV should start treatment as soon as possible to protect their own health and prevent transmission to the baby.
Prognosis
A Manageable Long-Term Condition
WHO states that with access to effective prevention, diagnosis, treatment and care, HIV infection has become a manageable chronic health condition that allows people to live long and healthy lives.
Treatment Works at Scale
WHO reported for 2025 that 88% of people living with HIV knew their status, 89% of those were on treatment, and 95% of those on treatment had suppressed viral loads.
Untreated Advanced Disease Is Fatal
CDC states that without treatment, people with AIDS typically survive about three years. This is why late diagnosis matters so much.
Lifelong Follow-Up
Viral load and CD4 monitoring continue through life to confirm that treatment is still working.
Differential Diagnosis
Infectious Mononucleosis
Glandular fever causes the same fever, sore throat and swollen glands as early HIV and is separated by specific Epstein-Barr virus testing.
Tuberculosis
Tuberculosis causes cough, fever, night sweats and weight loss that overlap with advanced HIV, and the two frequently occur together, so both are tested for.
Viral Hepatitis
Hepatitis B and C share the fever and malaise of early HIV and some routes of transmission, and are separated by hepatitis serology.
Malaria
In endemic areas an early fever is often assumed to be malaria, which is why a negative malaria test in a person with ongoing fever should prompt further testing.
Other Causes of Immune Suppression
Severe malnutrition and treatment such as chemotherapy produce similar infections, and are separated by a negative HIV test alongside the relevant history.
References
World Health Organization: HIV and AIDS
WHO fact sheet covering global burden, transmission, prevention, testing and treatment.
CDC: About HIV
Overview of HIV stages, transmission and the basis of treatment.
CDC: Getting Tested for HIV
Test types, detection windows and testing recommendations.
CDC: Treating HIV
Antiretroviral therapy, injectable options and viral suppression.
Frequently Asked Questions
Can HIV be cured?
No. WHO states there is no cure for HIV infection. Antiretroviral therapy suppresses the virus, stops the disease progressing and lets the immune system recover, but it has to be taken for life.
If I am on treatment, can I still pass HIV to my partner?
WHO states that people living with HIV who take antiretroviral therapy and have no detectable virus in their blood will not pass the virus to their sexual partners. CDC summarises this as undetectable equals untransmittable.
How soon after exposure will a test show HIV?
It depends on the test. CDC gives 10 to 33 days for a nucleic acid test, 18 to 45 days for a laboratory antigen and antibody test, 18 to 90 days for a rapid antigen and antibody test, and 23 to 90 days for antibody tests.
I think I was exposed last night. Is there anything I can take?
Yes. CDC states that post-exposure prophylaxis can prevent HIV after a possible exposure, must be started within 72 hours, and is taken daily for 28 days. Go to a clinic or emergency department the same day.
Can I have a baby without passing HIV to my child?
Yes, in most cases. WHO states that pregnant women living with HIV should start antiretroviral therapy as soon as possible, which protects the mother and helps prevent transmission before birth and through breast milk. Babies born to mothers with HIV are tested from birth or at 6 weeks.