Human immunodeficiency virus (HIV)

Overview

Human immunodeficiency virus (HIV) is a retrovirus that attacks the immune system, specifically the CD4 cells (T cells), which help the immune system fight infections. If left untreated, HIV can cause a weakened immune system or acquired immunodeficiency syndrome (AIDS). AIDS is a late or advanced stage of HIV infection that occurs when the CD4 cell count falls below 200 cells/mm³ or when an individual develops one or more opportunistic infections regardless of the CD4 count.

HIV can be treated and prevented with antiretroviral therapy (ART). While there is no cure for HIV, it is now considered a manageable chronic condition.

Disease epidemiology

According to the Joint United Nations Programme on HIV/AIDS (UNAIDS), approximately 1.3 million people are diagnosed with HIV worldwide and 630,000 people died of AIDS-related illness in 2022. It disproportionately affects resource-poor countries and certain groups of populations, including men who have sex with men (MSM), sex workers and their clients, and people who inject drugs.

In 2022, there were 202 new cases of HIV infections reported among Singapore residents. 51% of the new cases had late-stage HIV infection when they were diagnosed. Sexual intercourse remains the main mode of HIV transmission, accounting for 93% of cases. Heterosexual transmission accounted for 37% of all cases, while 51% and 4% of cases were due to homosexual and bisexual transmissions respectively.  

Pathogen(s)

Human immunodeficiency virus I and II.

Transmission

HIV is primarily transmitted through contact with certain bodily fluids (blood, breast milk, semen, or vaginal fluids) from a person with HIV, sharing contaminated needles and syringes, or mother-to-child transmission during childbirth or breastfeeding.

Incubation period:  The time from infection to development of detectable antibodies is generally one to three months. Between one and six weeks (median three weeks) after exposure to HIV, some infected individuals may develop a mononucleosis-like illness referred to as the acute retroviral syndrome. Without treatment, about half of infected adults will develop AIDS within 10 years after infection.

Infectious period: Individual is infectious throughout the entire duration but is most infectious during the period of seroconversion and untreated late-stage disease when the viral load (measured as number of HIV copies/ml plasma) is very high. However, if patient achieves durable viral suppression on treatment, they will not be able to transmit the virus to their sexual partner, a concept known as undetectable equals untransmittable (U=U).

Clinical features

HIV infection progresses through four different stages:

• Seroconversion Illness / Acute Retroviral Syndrome
  Mononucleosis-like illness. Combination of more than one of the following symptoms: fever, adenopathy, rash, sore throat, myalgia, diarrhoea, nausea, vomiting, headache, weight loss, or oral thrush. Some have oral and genital ulcerations and neurological illnesses (e.g. aseptic meningitis). The symptoms usually resolve spontaneously in most patients. Majority of infected cases experience this but condition is under-diagnosed. The median duration is 20 days, but it could range from less than a week to three months).

• Asymptomatic (“Latent”) Disease
  No specific symptoms or signs of infection, but active viral replication and immune destruction (declining CD4 counts) occurs throughout this period. Lymphadenopathy (often not noticed by patient) is usually present.

• Symptomatic Disease
  Symptoms include:

  • Fever

  • Weight loss

  • Persistent generalised lymphadenopathy

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

  • Immunological conditions (e.g. idiopathic thrombocytopenic purpura, multiple drug allergies)

• AIDS
  The development of a specific indicator disease including:

  • Viral: Persistent HSV ulceration for more than 1 month); CMV retinitis or disease other than liver, spleen, lymph node involvement.

  • Bacterial: Tuberculosis (esp. 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: e.g. non-Hodgkin’s lymphoma, CNS lymphoma, Kaposi’s sarcoma, cervical cancer.

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

Risk factors

Risk factors include:

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

• Having multiple sex partners;Inconsistent condom use if the relationship is not monogamous

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

• Sharing needles, syringes or other drug injection equipment

• Persons who exchange sex for money or drugs

• History or current presence of other STIs

Diagnosis

HIV testing can be classified into rapid and conventional. Rapid point-of-care tests (POCT) tests can be done directly at the site and yield results in 15 to 20 minutes. If a rapid HIV test returns positive, a separate blood sample for a confirmatory HIV lab test must be done before the diagnosis can be confirmed. Conventional tests are those in which blood is collected and then sent to the laboratory for testing. Results from conventional tests are typically available from a few hours to a few days. HIV self-testing kits are also available as of August 2022 as part of a pilot programme.

HIV tests are very accurate, but no test can detect the virus immediately after infection. The window period varies from person to person and is also dependent on the type of HIV test. A negative test should be repeated one and three months after the last high-risk exposure for confirmation.

Refer to NHIVP's HIV Testing Recommendations for more information.

Treatment and management

ART is recommended for all individuals with HIV, regardless of CD4 cell count. It should be started for all individuals within two weeks of presentation to care, barring several exceptions:

• Tuberculosis (TB):  ART should be started within 2 weeks of TB treatment initiation for patients with a CD4 count less than 50 cells/mm³, and started within 2–8 weeks of TB treatment initiation if the CD4 count is more than 50 cells/mm³.

• CMV Retinitis: Initiation of ART should be individualised. Joint management by a HIV physician and an ophthalmologist with expertise in managing CMV retinitis is required.

• CNS Opportunistic Infections (OIs): ART should be delayed in patients with CNS OIs until specific treatment for these OIs has been initiated, and clinical improvement observed.

 The goals of ART treatment are to:

• Achieve undetectable HIV viral loads

• To reduce HIV-associated morbidity

• Prolong the duration and quality of survival

• Prevent HIV transmission (also known as Treatment as Prevention, TasP)

Refer to NHIVP’s ART Recommendations for more information.

Precaution, prevention, and control

The NHIVP recommends people aged 21 years old and above or those who are sexually active should undergo HIV testing at least once in their lifetime. HIV testing is also recommended for the following persons:

• People diagnosed with TB.

• People seeking treatment for STIs.

• Individuals with symptoms suggesting HIV-related illnesses and AIDS-defining illnesses.

• Pregnant women at their first antenatal visit.

• Individuals at risk of HIV infection based on their behaviours.

Repeat screening should be performed at least annually for the following populations with high-risk behaviours:

• Sexual partners of HIV-infected persons whose viral load is above the limit of detection, especially if RNA is more than 200 copies/ml.

• Persons who are currently on pre-exposure prophylaxis (PrEP).

• Persons seeking treatment for or diagnosed with STIs (including viral hepatitis) should be routinely screened at each visit for a new complaint.

• Persons who exchange sex for money, and the partners of such persons.

• Persons with a history of injection drug use or who engage in sexual activities under the influence of alcohol or other drugs, and the partners of such persons.

• Persons with multiple sexual partners.

• More frequent screening than annual for certain individuals might be indicated based on risk behaviours.

Prevention of HIV:

• Using condoms consistently and correctly use of condoms when engaging in sexual activity.

• Limiting the number of sex partners.

• Getting tested for STIs and HIV regularly.

• Taking PrEP and post-exposure prophylaxis (PEP) for individuals at risk of HIV infection.

• Not injecting drugs.

Management of sexual contacts:

HIV-infected patients should be encouraged to inform their partners and refer them for counselling and testing. This can be assisted by medical social workers and counsellors.

Notification

HIV is a notifiable disease.

Who should notify:

• Medical practitioners

• Laboratories

When to notify:

• On clinical suspicion or laboratory confirmation

How to notify:

• Please refer to the Infectious Disease Notifications for more information.

Notification timeline:

• Within 72 hours from time of diagnosis

Resources

Refer to MOH's website for the updates on the HIV/AIDS situation in Singapore.

Refer to the National HIV Hepatitis C and STI programmes page for national guidelines and recommendations for:

• HIV Testing

• PrEP Guidance

• ART Recommendations

• Primary Care Recommendations

References

• Department of Sexually Transmitted Infections Control (DSC). STI management guidelines 7^th edition. 2021.

• Joint United Nations Programme on HIV/AIDS (UNAIDS). Global HIV & AIDS statistics — 2022 fact sheet. In: UNAIDS Global HIV & AIDS statistics [Internet]. 2022.