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Human immunodeficiency virus (HIV)

Human immunodeficiency virus (HIV) is a virus that weakens your body’s immune system by destroying CD4 (T-cell) lymphocytes.

Last updated 2 April 2025

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What is human immunodeficiency virus (HIV)?
What is acquired immunodeficiency syndrome (AIDS)?
How is HIV transmitted?
What are the symptoms of HIV?
What are the risk factors?
How to test for HIV? 
Understanding HIV test results
What to do when diagnosed with HIV?
How to prevent HIV?
What is pre-exposure prophylaxis (PrEP) treatment?
What is post-exposure prophylaxis (PEP) treatment?
How to treat HIV?
Educational materials
About the National HIV Programme

What is human immunodeficiency virus (HIV)?

HIV is a virus that weakens your body’s immune system by destroying CD4 (T-cell) lymphocytes. It is spread through bodily fluids like breast milk, blood, semen, or vaginal discharge from a person living with HIV. 

Most people contract HIV through unprotected sex, sharing or using unsanitised drug equipment like needles, or not taking medication to prevent or treat HIV. If untreated, HIV can lead to acquired immunodeficiency syndrome (AIDS). 

What is acquired immunodeficiency syndrome (AIDS)?

AIDS is an advanced stage of HIV infection, causing your immune system to be severely weakened. You receive an AIDS diagnosis when:

  • Your CD4 cell count falls below 200 cells/mm3; or

  • You develop one or more opportunistic infections regardless of your CD4 cell count.

For reference, a healthy CD4 cell count is above 500 cells/mm3.

How is HIV transmitted?

HIV is transmitted through:

  • Unprotected vaginal or anal sex with an infected person

  • Sharing of contaminated needles and sharps

  • Infected women transmitting HIV to their baby during pregnancy, birth, or breastfeeding

  • Contact with infected blood and blood products (e.g. organs, plasma)

HIV does not spread via:

  • Shaking hands, hugging, or touching

  • Saliva, tears, or sweat

  • Kissing

  • Coughing or sneezing

  • Sharing food and drinks

  • Toilet seats

  • Touching of common surfaces

  • Mosquitoes, ticks, or other insects

  • Air or water

  • Drinking fountains

What are the symptoms of HIV?

HIV infection progresses through four different stages:

Seroconversion Illness/Acute Retroviral Syndrome 

This stage is characterised by flu-like symptoms like fever, swelling of the lymph nodes, rash, sore throat, muscle pain, diarrhoea, nausea, vomiting, headache, weight loss, or oral thrush. Some individuals may have oral and genital ulcerations and neurological illnesses like aseptic meningitis. The symptoms usually resolve on their own in most patients. The median duration is 20 days, but it could range from less than a week to three months.

Asymptomatic (“Latent”) Disease

There are no specific symptoms or signs in this stage, but the virus is actively replicating and destroying the immune system by reducing CD4 cell count. Swollen lymph nodes, which are often not noticed by the patient, are usually present.

Symptomatic Disease

This stage presents more obvious symptoms such as:

  • Fever

  • Weight loss

  • Swollen lymph nodes

  • Skin and oral conditions (such as oral thrush, hairy leukoplakia, herpes zoster, recurrent herpes simplex)

  • Immunological conditions (such as having idiopathic thrombocytopenic purpura, multiple drug allergies)

AIDS

The last stage of infection is characterised by:

  • CD4 cell count falling below 200 cells/mm3

  • Developing one or more opportunistic infections regardless of theCD4 cell count

Opportunistic infections include:

  • Viral: Persistent HSV ulceration for more than 1 month; Cytomegalovirus retinitis (retinal inflammation) or diseases involving body parts other than the liver, spleen, or lymph nodes

  • Bacterial: Tuberculosis (especially extrapulmonary); atypical mycobacteria infections; recurrent bacterial pneumonia (2 or more episodes in 1 year); recurrent non-typhoid-salmonella septicaemia

  • Fungi: Oesophageal candidiasis; cryptococcal meningitis; histoplasmosis (extra-pulmonary); pneumocystis jiroveci pneumonia

  • Protozoa: Cerebral toxoplasmosis; cryptosporidial diarrhoea

  • Selected tumours: Non-Hodgkin’s lymphoma; CNS lymphoma; Kaposi’s sarcoma; cervical cancer

  • Others: Wasting; dementia; progressive multi-focal leucoencepholopathy

What are the risk factors?

Risk factors include:

  • Unprotected sex with a person who has a HIV detectable viral load

  • Having multiple sexual partners

  • Inconsistent condom use

  • Engaging in sexual activities under the influence of alcohol or other drugs

  • Sharing needles, syringes or other drug injection equipment

  • Exchanging sex for money or drugs 

  • History or current presence of other STIs

How to test for HIV? 

Getting tested for HIV is the only way to know your status. Delaying detection and diagnosis could lead to poorer prognosis and treatment outcomes, increasing the risk of transmission.

In Singapore, HIV testing is typically performed in hospitals, clinics, and community-based organisations. Some sites provide anonymous or rapid testing services, where the latter can provide results in 20 minutes. 

You can also use HIV self-test kits. They can be purchased at selected retail pharmacies nationwide and Action for AIDS (AfA).

Learn about HIV self-testing here.

Understanding HIV test results

You tested negative for HIV. What’s next?

A negative result means there were no signs of a HIV infection in your sample. However, you might still be infected because HIV takes about one to six weeks to incubate. The time between potential exposure and testing is called the window period.

Different HIV tests have different window periods. Ask your healthcare provider about the window period for the HIV test you are taking. For HIV self-test kits, you can find the information in the package. 

If you have a negative HIV test result and the last possible HIV exposure was:

Less than 72 hours ago

You may need post-exposure prophylaxis (PEP).

Less than 90 days ago

You will need to repeat the HIV test.

If you get a negative test result again after the window period, and have no possible HIV exposure during that time, then you do not have HIV. 

You tested HIV positive, What’s next?

All positive test results require a follow-up test for confirmation. 

If you test positive:

On a HIV self-test kit

Repeat the testing at a healthcare facility; includes anonymous testing sites.

At a healthcare facility

Repeat testing will be done automatically.

If you get a positive test result again, it means you have HIV. 

What to do when diagnosed with HIV?

There is currently no effective cure for HIV, but it can be controlled with proper care. This can be done through antiretroviral therapy (ART). With early detection and treatment, people living with HIV can live long, healthy lives, and protect their partners. 

HIV treatment is available in most public hospitals like the National Centre for Infectious Diseases (NCID), National University Hospital (NUH), Singapore General Hospital (SGH), and Changi General Hospital (CGH); and private healthcare institutions in Singapore.

Most HIV medications are subsidised, making them accessible and affordable. 

How to prevent HIV?

Staying HIV negative means:

  • Practising the ABCD approach to prevent HIV (Abstinence from casual sex, Be faithful, Correct and consistent condom usage, and early Detection)

  • Considering taking pre-exposure prophylaxis (PrEP) treatment if there is ongoing risk (see PrEP below under ‘HIV Prevention and Treatment’)

  • Testing regularly for HIV, or every 3–6 months if you engage in risky behaviours   

What is pre-exposure prophylaxis (PrEP) treatment?

Pre-exposure Prophylaxis (PrEP) is a risk-reduction treatment against HIV. When taken as prescribed, PrEP is highly effective at preventing HIV infection. PrEP only protects against HIV, so condom use is still important to prevent other sexually transmitted infections (STIs). 

Find out if PrEP is suitable for you here. 

Talk to your doctor if you are interested in PrEP.

What is post-exposure prophylaxis (PEP) treatment?

Post-exposure prophylaxis (PEP) is a short course of HIV medicine to prevent its transmission. It must be used within 72 hours of possible high-risk exposure and should only be used during emergencies. High-risk exposure to HIV includes:

  • Any unprotected anal or vaginal sex with someone who is HIV positive or belongs to a HIV-risk group (commercial sex workers, IV drug users, men who have sex with men, or bisexual men)

  • Sharing or exposure to contaminated needles or blades, particularly needle-stick injuries

  • Victims of sexual assault

PEP is not meant for regular use, and it is not a substitute for other HIV prevention methods such as consistent condom use. You should consider PrEP instead if you are repeatedly exposed to HIV.

Talk to your doctor if you think you need PEP. Should you require PEP during emergencies, please visit the Emergency Department of any public hospital and request for it.

How to treat HIV?

What is antiretroviral therapy (ART)?

Antiretroviral Therapy (ART) is recommended for all individuals living with HIV. Although ART cannot cure HIV, it can control the virus and help them live longer, healthier lives. ART can also reduce the risk of HIV transmission, but it does not prevent transmission of other STIs.

What is Treatment as Prevention (TasP)?

Treatment as Prevention (TasP) refers to the use of HIV medicine to decrease the risk of HIV transmission. People living with HIV who take the medicine as prescribed can suppress their HIV viral load to an undetectable level (less than 50 copies/ml), reducing the risk of HIV transmission to others (i.e. Undetectable = Untransmittable, U=U).

Educational materials

National HIV recommendations and guidelines 

Developed by the National HIV Programme (NHIVP), the following recommendations and guidelines are used to promote HIV prevention, treatment, and care:

  • HIV Testing Recommendations

  • Pre-Exposure Prophylaxis (PrEP) Guidance

  • Antiretroviral Therapy (ART) Recommendations 

  • Primary Care Recommendations

Find the guidelines here.

National campaigns

The NHIVP and its partners develop education campaigns aimed at debunking HIV myths and misconceptions, promoting HIV prevention, testing and treatment, and stopping HIV stigma. 

HIV Doesn’t Differentiate (2022 to 2024)

Content Pieces

With Early and Effective Treatment, People Living with HIV Can Lead Lives No Different from Others (2021) 

Content Pieces

It’s Time to Spread the Facts (2019)

Articles in media and publications

About the National HIV Programme

The National HIV Programme (NHIVP) sets the framework for managing and mitigating the impact of HIV/AIDS within Singapore. Led by the Ministry of Health (MOH) and administered by the Communicable Diseases Agency (CDA), NHIVP encompasses clinical HIV management; formulation and recommendations for national guidelines and policymaking; surveillance; training of healthcare workers; and public education campaigns. Get more information on the programme here.