What Are HIV and AIDS? Transmission, Symptoms, Testing, Prevention and Treatment

Created: 29.11.2024 · Last Updated: 10.08.2026 · Category: Infectious Diseases · Prepared by the Academic Hospital Web and Editorial Board.

HIV, or human immunodeficiency virus, is a virus that targets the immune system, particularly CD4 T lymphocytes. Without treatment, it can progressively weaken the body's ability to fight infections and certain diseases.

AIDS, or acquired immunodeficiency syndrome, is not another name for HIV. It is the most advanced stage of HIV infection, occurring when the immune system has become severely compromised.

Modern antiretroviral therapy can suppress HIV very effectively. With early diagnosis, appropriate treatment and regular follow-up, many people living with HIV can maintain their health, prevent progression to AIDS and live long, healthy lives.

What Is HIV?

After entering the body, HIV primarily targets CD4 T lymphocytes, which play an important role in coordinating immune responses.

Without effective treatment, HIV infection can progress through three stages:

  1. Acute HIV infection: The earliest stage following acquisition of HIV.
  2. Chronic HIV infection: A stage that may last for years without treatment and may cause few or no symptoms.
  3. AIDS: The most advanced stage, in which the immune system has been severely affected.
HIV and AIDS are not the same condition. HIV refers to the virus and infection. AIDS is the most advanced stage of untreated or inadequately controlled HIV infection. With modern treatment, progression to AIDS can usually be prevented.

What Is AIDS?

AIDS represents severe immune suppression caused by advanced HIV infection.

A person living with HIV may meet the criteria for AIDS if:

  • their CD4 count falls below 200 cells/mm³,
  • or they develop certain AIDS-defining opportunistic infections or conditions.

Opportunistic infections are infections that may become severe when the immune system is significantly weakened.

Starting and maintaining effective antiretroviral therapy can prevent HIV from progressing to AIDS in most people.

How Is HIV Transmitted?

HIV is transmitted when certain body fluids containing HIV reach another person's bloodstream or vulnerable mucous membranes.

Body fluids that can transmit HIV include:

  • Blood
  • Semen
  • Pre-seminal fluid
  • Vaginal fluids
  • Rectal fluids
  • Breast milk

Sexual Transmission

HIV can be transmitted through vaginal or anal sex when effective prevention is not being used and the partner with HIV is not virally suppressed.

Receptive anal sex carries a higher HIV transmission risk than vaginal sex.

Oral sex carries a much lower HIV risk than anal or vaginal sex. Current CDC guidance describes the chance of acquiring HIV through oral sex as little to no risk. Other sexually transmitted infections can, however, be transmitted through oral sex.

Blood and Shared Injection Equipment

Sharing needles, syringes or other injection equipment can transmit HIV if contaminated blood enters another person's bloodstream.

Occupational exposure to HIV-containing blood, such as certain needlestick injuries in healthcare settings, also requires prompt risk assessment.

Pregnancy, Birth and Breastfeeding

HIV can be transmitted during pregnancy, labour, delivery or breastfeeding. Effective antiretroviral therapy and appropriate specialist care can substantially reduce the likelihood of transmission to the baby.

Blood Transfusion and Organ Transplantation

HIV can theoretically be transmitted through infected blood or donated organs. In modern healthcare systems, systematic donor screening has made this route extremely uncommon.

How Is HIV Not Transmitted?

HIV is not spread through ordinary social contact.

You cannot acquire HIV from:

  • Shaking hands
  • Hugging
  • Being in the same room
  • Sharing toilets
  • Sharing plates, glasses or cutlery
  • Swimming pools
  • Coughing or sneezing
  • Sweat or tears
  • Mosquito or insect bites

HIV is not transmitted through ordinary kissing or saliva.

HIV is not transmitted through everyday contact. Living, working or socialising with a person living with HIV does not create a risk of HIV transmission.

What Are the Symptoms of HIV?

HIV symptoms vary between individuals, and some people may have no symptoms for a long period.

Acute HIV Infection

Some people develop a flu-like illness approximately 2 to 4 weeks after acquiring HIV.

Possible symptoms include:

  • Fever
  • Sore throat
  • Swollen lymph nodes
  • Rash
  • Muscle or joint pain
  • Headache
  • Marked fatigue

These symptoms are not specific to HIV and can occur with many other infections. Some people experience no symptoms during acute infection.

Chronic HIV Infection

Following the acute stage, HIV may cause no obvious symptoms for years. Looking or feeling healthy therefore does not establish that a person does not have HIV.

Advanced HIV / AIDS

When untreated HIV causes severe immune suppression, symptoms may be related to opportunistic infections or other HIV-associated conditions, including:

  • Recurrent or severe infections
  • Unexplained weight loss
  • Persistent fever
  • Night sweats
  • Persistent diarrhoea
  • Certain opportunistic infections
  • Certain cancers

Symptoms cannot confirm or exclude HIV. The only reliable way to know your HIV status is to have an appropriate HIV test.

Book an Appointment

When Should an HIV Test Be Done?

Testing is the only reliable way to determine HIV status.

The time between acquiring HIV and a test being able to detect the infection is known as the window period. A test performed too early may be negative even when infection has occurred.

According to CDC guidance, approximate detection windows include:

  • Laboratory antigen/antibody test using blood from a vein: Usually 18–45 days after exposure.
  • Rapid finger-stick antigen/antibody test: Approximately 18–90 days.
  • Antibody tests, including many self-tests: Approximately 23–90 days.
  • Nucleic acid test (NAT / HIV RNA): Usually approximately 10–33 days.

The appropriate test and timing depend on the exposure and clinical circumstances. PrEP or PEP may also affect testing strategies, so follow-up should be planned by a healthcare professional.

A negative test performed too early may not exclude HIV. Repeat testing after the appropriate window period may be required.

What Should You Do After a Possible HIV Exposure?

If a recent event may have exposed you to HIV, do not wait for symptoms or for a future HIV test before seeking medical advice. Post-exposure prophylaxis (PEP) may prevent HIV after certain exposures.

Time is critical for PEP. PEP should be started as soon as possible and no later than 72 hours after a potential exposure. Every hour counts. Seek urgent medical assessment if a possible HIV exposure occurred within the last 72 hours.

Whether PEP is appropriate depends on factors such as:

  • The type of exposure
  • The source person's HIV status and, where known, viral load
  • Whether a condom was used
  • Whether blood or another potentially infectious fluid was involved
  • How much time has passed since exposure

PEP usually involves 28 days of antiretroviral medication with appropriate baseline and follow-up testing.

What Are PrEP and PEP?

PrEP – Pre-Exposure Prophylaxis

PrEP is HIV prevention medication for people who do not have HIV and may be exposed to HIV through sex or injection drug use.

When taken or administered as prescribed, PrEP is highly effective at preventing HIV. Suitability and follow-up should be assessed by a healthcare professional with experience in HIV prevention.

PEP – Post-Exposure Prophylaxis

PEP is a short course of HIV medication used after a potential HIV exposure.

PEP:

  • Should be started as soon as possible
  • Must be started within 72 hours
  • Is usually taken for 28 days
  • Requires medical risk assessment and follow-up

How Is HIV Treated?

There is currently no routinely available treatment that completely eliminates HIV from the body. However, antiretroviral therapy (ART) can suppress HIV very effectively.

Current guidelines recommend ART for everyone living with HIV and recommend starting treatment as soon as possible after diagnosis.

The goals of ART include:

  • Suppressing HIV replication
  • Reducing viral load to an undetectable or very low level
  • Protecting and restoring immune function
  • Preventing progression to AIDS
  • Reducing opportunistic infections and HIV-related complications
  • Supporting a long and healthy life
  • Preventing onward HIV transmission

The most appropriate ART regimen depends on individual clinical factors, HIV resistance testing, other medical conditions and potential drug interactions.

Many people use once-daily oral regimens, while long-acting injectable treatment may be appropriate for selected patients.

What Does U=U Mean?

U=U means “Undetectable = Untransmittable.”

Scientific evidence shows that a person living with HIV who takes effective ART and maintains a suppressed viral load does not transmit HIV through sex.

Current NIH guidance states that maintaining an HIV viral load below 200 copies/mL with ART prevents sexual transmission of HIV.

U=U is supported by strong scientific evidence. A person who maintains viral suppression on HIV treatment does not transmit HIV through sex. Condoms remain useful for preventing other sexually transmitted infections and unintended pregnancy.

HIV and Pregnancy

HIV can be transmitted to a baby during pregnancy, childbirth or breastfeeding. Effective ART and coordinated specialist care can substantially reduce this risk.

Care may include:

  • Consistent maternal antiretroviral therapy
  • Regular viral load monitoring
  • Joint management by Infectious Diseases and Obstetrics teams
  • Individualised delivery planning
  • Appropriate preventive treatment for the baby
  • HIV testing of the infant at recommended intervals

Infant feeding recommendations may vary according to national guidance, maternal viral suppression and individual circumstances and should be discussed with the specialist care team.

How Can HIV Be Prevented?

Several highly effective strategies can reduce HIV transmission.

  • Condoms: Correct and consistent condom use reduces the risk of HIV and many other sexually transmitted infections during vaginal or anal sex.
  • PrEP: Can prevent HIV in appropriately selected people without HIV who may be exposed to the virus.
  • PEP: Emergency prevention medication that must be started within 72 hours of a potential exposure.
  • Do not share injection equipment.
  • HIV testing: Knowing HIV status supports early treatment and prevention.
  • ART and U=U: Maintaining viral suppression prevents sexual transmission of HIV.
  • Sexually transmitted infection screening: Testing and treatment may be recommended according to individual risk.

When Should You Seek Medical Advice?

Consider an Infectious Diseases assessment if:

  • You have had a sexual exposure that may carry HIV risk
  • You have been exposed to potentially HIV-containing blood
  • You have shared needles or injection equipment
  • An HIV screening test is reactive or positive
  • You would like to discuss PrEP
  • You are living with HIV and require treatment or follow-up
  • You are planning pregnancy and you or your partner is living with HIV

If a potential HIV exposure occurred within the last 72 hours, do not wait for a routine appointment. Seek urgent medical assessment for PEP as soon as possible.

Discuss HIV Testing, Prevention and Treatment

Possible exposure, HIV testing, PrEP, PEP and HIV treatment can be assessed individually by an Infectious Diseases specialist.

Frequently Asked Questions

Are HIV and AIDS the same thing?
No. HIV is the virus and infection that affects the immune system. AIDS is the advanced stage of untreated or inadequately controlled HIV infection in which the immune system has become severely compromised.
Can HIV be transmitted by kissing or hugging?
No. HIV is not transmitted through hugging, shaking hands, ordinary kissing, sharing plates or glasses, toilets, swimming pools or mosquito bites.
Can HIV be transmitted through oral sex?
The risk of HIV transmission through oral sex is much lower than through anal or vaginal sex and is considered little to no risk. Other sexually transmitted infections can still be transmitted through oral sex.
Can HIV be diagnosed from symptoms?
No. Some people develop flu-like symptoms 2 to 4 weeks after acquiring HIV, while others have no symptoms. The reliable way to determine HIV status is appropriate HIV testing.
When should an HIV test be done after exposure?
Timing depends on the test. A laboratory antigen/antibody test using venous blood usually detects HIV in 18–45 days, antibody tests in 23–90 days and a NAT in approximately 10–33 days. The appropriate test and repeat schedule should be determined by a healthcare professional.
How soon must PEP be started?
PEP should be started as soon as possible and no later than 72 hours after a potential HIV exposure. It is usually taken for 28 days, and suitability should be assessed by a healthcare professional.
Can HIV be treated?
There is no routinely available treatment that completely eliminates HIV from the body. However, antiretroviral therapy can suppress HIV very effectively, protect the immune system and allow people living with HIV to live long, healthy lives.
What does U=U mean?
U=U means “Undetectable = Untransmittable.” A person living with HIV who takes effective treatment and maintains a suppressed viral load does not transmit HIV to sexual partners.
Academic Hospital note: HIV can now be effectively controlled with early diagnosis and consistent antiretroviral treatment. Symptoms cannot reliably establish HIV status. You can book an Infectious Diseases appointment for HIV testing, PrEP, PEP, treatment or follow-up. If a possible exposure occurred within the last 72 hours, seek urgent medical assessment for PEP rather than waiting for a routine appointment.

References

  1. Academic Hospital. AIDS / HIV Enfeksiyonu Nedir? Nasıl Bulaşır? Tedavisi Nasıldır?
  2. World Health Organization. HIV and AIDS
  3. Centers for Disease Control and Prevention. About HIV
  4. Centers for Disease Control and Prevention. Getting Tested for HIV
  5. Centers for Disease Control and Prevention. Preventing HIV with PrEP
  6. Centers for Disease Control and Prevention. Preventing HIV with PEP
  7. HIVinfo, National Institutes of Health. The Stages of HIV Infection
  8. NIH ClinicalInfo. Initiation of Antiretroviral Therapy
  9. NIH ClinicalInfo. Antiretroviral Therapy to Prevent Sexual Transmission of HIV