HIV and AIDS: Causes, Symptoms, Diagnosis, Treatment and Prevention

HIV stands for human immunodeficiency virus. It is a virus that attacks the immune system, especially a type of white blood cell called the CD4 cell (or T-helper cell). These cells help the body fight infections and some cancers. Over time, untreated HIV destroys so many CD4 cells that the body can no longer defend itself properly.

AIDS stands for acquired immunodeficiency syndrome. It is the most advanced stage of HIV infection, when the immune system is severely damaged and the person develops serious infections or cancers known as opportunistic illnesses. Not everyone with HIV develops AIDS. With modern treatment, most people with HIV never reach this stage.

HIV has no cure, but it is now a manageable long-term condition. Taking daily medicines called antiretroviral therapy (ART) can reduce the virus in the blood to undetectable levels, keep the immune system healthy and allow people to live long lives. A person who keeps an undetectable viral level cannot pass HIV to sexual partners.

According to UNAIDS, around 40.8 million people were living with HIV worldwide at the end of 2024, with about 1.3 million new infections and about 630,000 AIDS-related deaths that year. Around 31.6 million people were receiving treatment. Many people with HIV do not know their status, which is why testing is so important.

A person can have HIV for many years without having AIDS. A person who has been diagnosed with AIDS still has HIV, and treatment can still improve their health.

• HIV-1: The most common type, responsible for the vast majority of infections worldwide.
• HIV-2: Less common, found mostly in West Africa. It is less easily transmitted and progresses more slowly, but it still needs treatment. Some HIV-1 medicines and tests work differently for HIV-2, so specialist advice is needed.

HIV is passed from one person to another through certain body fluids from a person with HIV who has a detectable viral load:

• Blood
• Semen and pre-seminal fluid
• Rectal fluids
• Vaginal fluids
• Breast milk

The virus must enter the bloodstream of another person through a mucous membrane (for example in the genitals, rectum or mouth), damaged tissue or direct injection.

Main routes of transmission

• Sex without a condom (vaginal, anal or, less commonly, oral) with a person who has HIV and is not on effective treatment. Anal sex carries the highest risk per act.
• Sharing needles, syringes and other drug equipment
• From mother to child during pregnancy, birth or breastfeeding. With treatment and proper care, the risk can be reduced to less than 1%. Without treatment, it can be between 15% and 45%.
• Blood transfusions and organ transplants from infected donors. This is now very rare in places where blood is screened.
• Unsafe medical, dental, tattooing or piercing procedures that use contaminated equipment
• Needlestick injuries, mostly affecting healthcare workers

How HIV is NOT spread

HIV does not spread through:

• Hugging, kissing, shaking hands or sharing a toilet
• Sharing food, drinks, plates, cups or towels
• Coughing or sneezing
• Sweat, tears or saliva (casual contact)
• Swimming pools
• Mosquitoes or other insects
• Working, studying or living with a person who has HIV

Undetectable = Untransmittable (U=U)

Large studies have shown that people with HIV who take ART and keep their viral load undetectable (usually below 200 copies/mL) for at least six months do not pass HIV to their sexual partners. This is known as U=U. It is one of the most important messages in HIV care, and it applies to sex. It does not remove all risk of passing HIV by sharing needles, and breastfeeding needs medical guidance.

Stage 1: Acute HIV infection

This occurs within about 2 to 4 weeks of infection. The virus multiplies very quickly, and the viral load is extremely high, so the person is highly infectious even if they feel unwell or have no symptoms. Many people experience a flu-like illness, but some have no symptoms at all.

Stage 2: Chronic HIV infection (clinical latency)

HIV continues to multiply at lower levels. Without treatment, this stage can last 10 years or longer, and there may be few or no symptoms. The person can still transmit HIV. With effective treatment, the virus can be kept at undetectable levels and this stage can last for decades.

Stage 3: AIDS

Without treatment, the CD4 count falls below 200 cells/mm³ (a healthy adult count is about 500 to 1,600), or the person develops an AIDS-defining illness. Without treatment, survival at this stage is typically about three years, and shorter if a dangerous opportunistic illness develops.

Early (acute) symptoms

About two to four weeks after exposure, some people develop symptoms that last from a few days to several weeks. They can include:

• Fever
• Sore throat
• Swollen lymph nodes (glands) in the neck, armpits or groin
• Rash
• Fatigue
• Muscle and joint aches
• Headache
• Mouth ulcers
• Night sweats
• Diarrhea

These symptoms are common in many illnesses, such as the flu, so they cannot be used to diagnose HIV. Only a test can.

Chronic stage

Many people have no symptoms for years. Others have mild or recurring problems such as swollen glands, fatigue, weight loss, repeated fevers, oral thrush, shingles or skin problems.

Symptoms of advanced HIV and AIDS

• Rapid weight loss and wasting
• Recurrent fever or drenching night sweats
• Extreme and unexplained tiredness
• Prolonged swelling of lymph nodes
• Diarrhea lasting more than a week
• White spots or unusual lesions in the mouth, tongue or throat
• Persistent cough or shortness of breath
• Pneumonia
• Blotches on or under the skin or inside the mouth, nose or eyelids that are red, brown, pink or purple
• Memory loss, confusion, depression or other neurological problems

When to see a doctor

Get tested if you think you have been exposed to HIV, if you have had unprotected sex or shared injecting equipment, or if you have symptoms and a possible risk. Do not wait for symptoms.

Seek urgent care if you think you were exposed within the past 72 hours. Starting post-exposure prophylaxis (PEP) as soon as possible can prevent infection.

When the immune system is weak, infections and cancers that rarely harm healthy people can become serious. Common examples include:

• Pneumocystis pneumonia (PCP): A fungal lung infection
• Tuberculosis (TB): The leading cause of death among people with HIV worldwide. HIV greatly increases the risk of developing active TB.
• Candidiasis: Thrush in the mouth, throat or esophagus
• Cryptococcal meningitis: A fungal infection of the brain and spinal cord lining
• Toxoplasmosis: A parasitic infection affecting the brain
• Cytomegalovirus (CMV) infection: Can affect the eyes, causing vision loss, as well as the gut and lungs
• Mycobacterium avium complex (MAC)
• Cryptosporidiosis: A parasitic infection causing severe diarrhea
• Kaposi sarcoma: A cancer caused by a herpes virus, producing purple or brown skin lesions
• Lymphomas: Including non-Hodgkin lymphoma
• Cervical cancer and anal cancer: Linked to human papillomavirus (HPV)
• HIV-associated neurocognitive disorders and wasting syndrome

Starting ART early and taking preventive medicines when needed greatly lowers the risk of these complications.

HIV can only be diagnosed by testing. Testing is simple, widely available and often free or confidential.

Types of tests

• Antigen/antibody tests (4th generation): Detect both HIV antibodies and the p24 antigen, a part of the virus. They are usually done in a laboratory on blood from a vein. They can detect infection about 18 to 45 days after exposure. Rapid finger-prick versions may take up to 90 days.
• Antibody tests: Detect antibodies produced by the body. Most rapid tests and home self-tests are antibody tests, and they may need up to 3 months after exposure to be fully reliable.
• Nucleic acid tests (NAT): Detect the virus itself and can find HIV about 10 to 33 days after exposure. They are used when acute HIV is suspected, and also to diagnose infants born to mothers with HIV.

The window period

The window period is the time between exposure to HIV and when a test can reliably detect it. If you test during this time and the result is negative, you should repeat the test after the window period has passed. During the window period, a person can still pass on HIV.

After a positive result

A positive screening test is confirmed with further testing, following national guidelines. A confirmed diagnosis is followed by:

• CD4 count: Shows how strong the immune system is
• Viral load: Measures how much HIV is in the blood
• Drug-resistance testing: Checks whether the virus is resistant to any HIV medicines
• Screening for other infections: Such as TB, hepatitis B and C, syphilis and other sexually transmitted infections
• General health checks: Kidney and liver function, blood counts, cholesterol and blood sugar, and cervical screening for women

Who should get tested

Health agencies recommend that everyone should be tested at least once, and more often for people at higher risk. This includes people with multiple partners, men who have sex with men, people who inject drugs, people with other sexually transmitted infections, people with TB, and pregnant women. Anyone who may have been exposed should test.

Antiretroviral therapy (ART)

ART is the standard treatment for HIV. It uses a combination of medicines that block HIV at different stages of its life cycle. ART does not cure HIV, but it:

• Lowers the viral load to undetectable levels
• Allows the immune system to recover
• Prevents progression to AIDS
• Prevents transmission to others
• Reduces the risk of many HIV-related illnesses

Treatment is recommended for everyone diagnosed with HIV, as soon as possible, regardless of CD4 count.

Main drug classes include:

• Integrase strand transfer inhibitors (INSTIs): Such as dolutegravir, bictegravir and raltegravir. These are widely used first-line medicines.
• Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs): Such as tenofovir, emtricitabine, lamivudine and abacavir. These are the backbone of most regimens.
• Non-nucleoside reverse transcriptase inhibitors (NNRTIs): Such as rilpivirine and doravirine
• Protease inhibitors (PIs): Such as darunavir
• Other classes: Including entry inhibitors and capsid inhibitors, used in treatment-experienced patients

Many modern regimens combine several drugs into one tablet taken once a day. Long-acting injectable treatment with cabotegravir and rilpivirine, given every one or two months, is also available in some countries for people whose virus is already well controlled.

Taking ART successfully

• Take medicines every day, at the same time, exactly as prescribed. Missed doses can allow the virus to become resistant, making treatment less effective.
• Do not stop or change medicines without medical advice.
• Tell your doctor about all other medicines, herbal products and supplements, because some interact with ART.
• Report side effects early. Many can be managed or the regimen can be changed.
• Attend regular check-ups and viral load tests. After starting ART, viral load is usually checked at around 4 to 8 weeks, then every few months until it is stable, and at least once or twice a year after that.

Possible side effects

Side effects vary by medicine and person. Many appear in the first weeks and settle. They can include nausea, diarrhea, headache, tiredness, sleep problems, rash and mood changes. Longer-term effects can include changes in cholesterol or blood sugar, weight gain, kidney or bone effects, and, with some older medicines, nerve problems or changes in body fat. Modern regimens are generally much better tolerated than older ones.

Preventing and treating opportunistic infections

• Cotrimoxazole prophylaxis: A daily antibiotic that helps prevent PCP, toxoplasmosis and some other infections in people with low CD4 counts
• TB screening and preventive treatment: People with HIV should be checked for TB and offered preventive therapy if they do not have active TB
• Treatment of specific infections: With antifungals, antibiotics, antivirals or other medicines
• Vaccinations: Such as influenza, pneumococcal, hepatitis A and B, HPV and COVID-19, as advised. Live vaccines may not be suitable for people with very low CD4 counts.

Immune reconstitution inflammatory syndrome (IRIS)

In some people with very advanced HIV, starting ART can cause the recovering immune system to react strongly to an existing infection, producing a temporary worsening of symptoms. Doctors know how to watch for and manage this, and it is not a reason to stop treatment.

There are many effective ways to prevent HIV, and they work best in combination.

Condoms and safer sex

• Correct and consistent use of male or female condoms during vaginal and anal sex greatly reduces the risk of HIV and many other sexually transmitted infections.
• Use water-based or silicone-based lubricants with latex condoms.
• Get tested and treated for sexually transmitted infections, since they can raise HIV risk.

Pre-exposure prophylaxis (PrEP)

PrEP is medicine taken by people who do not have HIV to prevent infection. When used as directed, it is highly effective.

• Daily oral PrEP: Tablets containing tenofovir with emtricitabine (or tenofovir alafenamide with emtricitabine for some people)
• Event-driven (on-demand) oral PrEP: Used in some guidelines for men who have sex with men
• Long-acting injectable PrEP: Cabotegravir, given every two months
• Lenacapavir: A twice-yearly injection approved in 2025 for HIV prevention in some countries. Availability and access differ by country.

PrEP does not protect against other sexually transmitted infections or pregnancy. People taking PrEP need regular HIV tests and kidney checks, as advised by their healthcare provider.

Post-exposure prophylaxis (PEP)

PEP is a short course of antiretroviral medicines, taken for about 28 days, to prevent infection after a possible exposure. It must be started as soon as possible, ideally within hours and no later than 72 hours after exposure. It is used after unprotected sex, sexual assault, needlestick injuries or other high-risk exposures. Go to an emergency department or sexual health clinic immediately.

Treatment as prevention (U=U)

Treating people with HIV so their viral load is undetectable protects their partners, as explained above.

Harm reduction for people who inject drugs

• Use new, sterile needles and syringes every time, and never share equipment
• Needle and syringe programs, opioid substitution therapy (such as methadone or buprenorphine) and drug treatment services reduce risk

Preventing mother-to-child transmission

• Every pregnant woman should be offered an HIV test.
• Women with HIV should start ART as soon as possible and continue it through pregnancy, delivery and breastfeeding, if breastfeeding is chosen.
• Babies born to mothers with HIV receive preventive medicine and testing.
• With these steps, most babies are born HIV-free, and many countries have eliminated mother-to-child transmission.

Medical and other settings

• Use only sterile equipment for injections, dental care, tattoos and piercings.
• Healthcare workers should follow standard precautions and use safe sharps handling.
• Blood supplies should be screened for HIV.

Voluntary medical male circumcision

In areas with high rates of HIV, voluntary medical male circumcision reduces the risk of a man becoming infected through vaginal sex by about 60%. It does not provide complete protection and should be combined with other prevention.

With early diagnosis and good treatment, a person with HIV can expect to live a near-normal lifespan and have a good quality of life.

• Stay on treatment and attend regular check-ups.
• Look after your overall health. Eat a balanced diet, stay physically active, avoid smoking, limit alcohol and avoid recreational drug use. People with HIV have higher risks of heart disease, bone loss and some cancers, so general health screening is important.
• Keep up with screening and vaccinations. This includes cervical or anal cancer screening, TB checks and other tests your care team recommends.
• Protect your mental health. Anxiety, depression and loneliness are common after diagnosis. Counseling, peer support groups and talking with trusted people can help.
• Relationships and sex. People with an undetectable viral load do not pass HIV to sexual partners. Talk to partners about HIV status and prevention, and consider testing, PrEP and condoms as appropriate.
• Pregnancy and family planning. Many women with HIV have healthy babies with the right care. Men and women with HIV can discuss safe conception options with their doctor.
• Disclosure. Telling others about your HIV status is a personal decision. A healthcare provider or counselor can help you decide who to tell and how.
• Legal rights. In many countries, laws protect people with HIV from discrimination at work, school and in healthcare. Seek local advice if you face discrimination.

Stigma and discrimination

Stigma remains one of the biggest barriers to testing, treatment and care. HIV is a medical condition, not a moral failing. Using respectful language, learning the facts and supporting people living with HIV helps reduce stigma and saves lives.

• “HIV and AIDS are the same thing.” HIV is the virus. AIDS is the advanced stage that can develop if HIV is not treated.
• “HIV is a death sentence.” With modern treatment, people with HIV can live long, healthy lives.
• “You can get HIV from hugging, kissing, sharing food or toilets.” HIV does not spread through casual contact.
• “Mosquitoes can spread HIV.” They cannot.
• “I would know if I had HIV.” Many people have no symptoms for years. Only a test can show if you have HIV.
• “Only certain groups get HIV.” Anyone can get HIV, regardless of age, sex, sexual orientation, race or background. What matters is behavior and exposure, not identity.
• “People with HIV cannot have healthy babies.” With treatment and proper care, most babies born to mothers with HIV are born without HIV.
• “If my partner is on treatment, I will get HIV.” If your partner’s viral load is undetectable, there is effectively no risk of sexual transmission.
• “There is a herbal or natural cure for HIV.” No herbal remedy or supplement cures HIV, and stopping ART in favor of such products can be life-threatening.
• “Two people with HIV do not need to use condoms.” Condoms still help prevent other sexually transmitted infections, and there is a small risk of passing on a different strain, especially if one partner’s virus is not suppressed.
• “A negative test right after exposure means I’m safe.” Because of the window period, you may need to test again.

Can HIV be cured?

There is currently no widely available cure. A very small number of people have been cured after stem cell transplants done for cancer, but this is not a practical treatment for most people. ART controls the virus effectively for life.

How long can someone live with HIV?

People who are diagnosed early and take ART consistently can have a life expectancy close to that of people without HIV.

How soon after exposure can I get tested?

It depends on the test. NAT tests can detect HIV after about 10 to 33 days. Laboratory antigen/antibody tests work from about 18 to 45 days. Self-tests and rapid antibody tests can take up to 3 months. If you test early and get a negative result, repeat the test later as advised.

Can HIV be passed through oral sex?

The risk is much lower than for anal or vaginal sex, but it is not zero, particularly if there are mouth sores or bleeding gums.

Can I get HIV from a person on treatment?

If the person has had an undetectable viral load for at least six months, there is effectively no risk of sexual transmission.

What is the difference between PrEP and PEP?

PrEP is taken before possible exposure, by people at ongoing risk. PEP is taken after a single possible exposure, within 72 hours, for 28 days.

Can a person with HIV breastfeed?

Guidance varies. Where safe infant feeding alternatives are available, formula is recommended in some countries. In many settings, WHO supports breastfeeding if the mother is on effective ART and has a suppressed viral load, with the baby also receiving preventive treatment. Mothers should discuss this with their healthcare team.

Can people with HIV donate blood?

No. Blood services do not accept donations from people with HIV.

Can I get HIV from a tattoo or piercing?

Only if non-sterile equipment contaminated with infected blood is used. Choose licensed studios that use new, sterile needles and equipment.

Is there a vaccine for HIV?

Not yet. Researchers are working on vaccines, but none is available.

Does HIV always lead to AIDS?

No. With effective treatment, most people with HIV never develop AIDS. Without treatment, most will eventually do so.

Where can I get tested?

You can be tested at government health clinics, hospitals, sexual health clinics, community centers, and many pharmacies. Home self-tests are available in many countries. Testing is usually confidential.

• World Health Organization. HIV and AIDS fact sheet: https://www.who.int/news-room/fact-sheets/detail/hiv-aids
• UNAIDS. Global HIV & AIDS statistics fact sheet: https://www.unaids.org/en/resources/fact-sheet
• Centers for Disease Control and Prevention. HIV: https://www.cdc.gov/hiv/
• National Institutes of Health. HIVinfo.NIH.gov (clinical and patient information): https://hivinfo.nih.gov
• National AIDS Control Organisation (NACO), India: https://naco.gov.in

This article is for general educational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. HIV care depends on the individual, so always talk to a qualified healthcare professional about your own risks, test results and treatment choices. If you think you were exposed to HIV in the last 72 hours, go immediately to an emergency department or sexual health clinic to ask about post-exposure prophylaxis. If you have difficulty breathing, severe headache with confusion, or any other medical emergency, contact your local emergency services or seek urgent care immediately.