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Causative Agent

Human immunodeficiency virus I and II

Incubation Period

Variable. The median incubation period is shorter in infants than in adults.

The time from infection to development of detectable antibodies is generally 1- 3months.

Between 1 and 6 weeks (median 3 weeks) after exposure to HIV, one half to two thirds of recently infected individuals 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.


Via sexual route (most common), transfusion of infected blood (or blood products) and contaminated needles; from mother-to-child during in-utero, intrapartum and perinatal period and via breastfeeding. Transmission after contact with saliva, tears, urine, stool and bronchial secretions has not been reported.

Infectious Period

Infectious for whole duration of infection; 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.


By the end of 2009, there were a total of 4404 cases reported in Singapore (2009 notification rate: 124 per million population). The majority (94%) were infected via the sexual route: heterosexual sex (66%), homosexual (21%) and bisexual (7%). Most cases (90%) are males with the highest proportion (32%) in the 30-39 years age group. There have been 29 children infected through mother-to-child transmission locally.

Progression through 4 stages; individuals with higher viral loads generally progress faster.

  • 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). Median duration of illness is 20 days (range < 1 week to 3 months). Resolves spontaneously in most patients. Majority of infected cases experience this but condition is under- diagnosed.
  • Asymptomatic (“latent”) disease
    No specific symptoms or signs of infection, but active viral replication and immune destruction (declining CD4 counts) is occurring throughout this period. Lymphadenopathy (often not noticed by patient) is usually present.
  • Symptomatic disease
    Fever, weight loss, persistent generalised lymphadenopathy, skin and oral conditions (oral thrush, hairy leukoplakia, herpes zoster, recurrent herpes simplex) and immunological conditions (e.g. idiopathic thrombocytopenic purpura, multiple drug allergies).
  • Acquired immune deficiency syndrome (AIDS)
    The development of a specific indicator disease including:
    • Viral: Persistent HSV ulceration (>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 one 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)

  • Serology: screening test (e.g. fourth generation antibody-P24 antigen combination test, rapid test kits) followed by confirmatory test (e.g. Western blot).
  • A signed consent is not needed for HIV testing. When HIV testing is medically indicated and carried out as part of the overall medical management of the patient, extensive pre-HIV test counselling is not required. However, just like in any diagnostic investigation, it is prudent to inform patients that you are doing this test and offer to answer any queries. You may want to document that patient is agreeable for HIV testing. Reasons for refusal should also be documented.
  • If a patient voluntarily requests HIV testing, e.g. because he has engaged in high-risk sexual behaviours, pre-HIV test counselling should be carried out for the patient. The implications of positive and negative test results and the patient’s potential risk factors should be discussed, and the patient educated on HIV infection and safer sex practices.
  • Direct viral testing (e.g. PCR) is not recommended as a diagnostic test (except in infants and children < 18 months of age) but utilized as a management tool to guide and monitor treatment.

Notify the National Public Health Unit, MOH using Form MD 131 (fax) or electronically via CD-LENS. Notification through CD-LENS is strongly encouraged.

HIV/AIDS cases should be notified if they have:

  • A positive result from a confirmatory HIV antibody test (e.g. Western blot);
  • A positive virological test for HIV or its components (HIV-RNA or HIV- DNA or HIV p24 antigen);
  • Clinically suspected or probable HIV infection (e.g. presence of AIDS- defining condition).

  • Post-test counselling (see below).
  • Referral to ID Physician for specialist care in HIV Medicine.
  • Effective therapy is available that can significantly prolong survival and reduce morbidity and infectivity.
  • Management includes:
    • antiretroviral therapy to prevent destruction of immune system
    • prophylaxis and treatment of opportunistic infections.

  • HIV in pregnant women
    • Ante-natal screening is advised, so that anti-HIV medications can be instituted.
    • Employing combination interventions during pregnancy, labour and post delivery (e.g. antiretroviral therapy, elective caesarean section and avoidance of breastfeeding) can markedly reduce the transmission to baby. Now, with combination therapy and undetectable maternal viral load, the risk is minimal (from about 23% to < 1-2 %).
  • Post-exposure prophylaxis for needle-stick injuries in HCW
    • Post-exposure antiretroviral prophylaxis significantly reduces risk of transmission of HIV (up to 80% risk reduction if started early).
    • Combination therapy with at least 2 – 3 drugs is recommended for all significant exposures (see Appendix 1 for details).
  • HIV in children: refer to ID physician, KK Women’s & Children’s Hospital.

    • Negative test
      • Explain results.
      • If risk activity within last 6 months, inform patient of window period and advise re-testing 3 months later.
      • Reinforce advice on risk reduction.
      • Reassure confidentiality.
    • Positive test
      • Reassure confidentiality.
      • Assess risk factors.
      • Explain results.
      • Provide basic information about HIV, AIDS and transmission.
      • Assess patient’s support system and coping mechanism.
      • Explain that very effective therapies are now available for HIV/AIDS treatment.
      • Advise that treatment cost has declined and treatment can be affordable. Medifund assistance for treatment is available for needy patients. Other funds are also available to help these patients.
      • Explain the need for further medical assessment and long-term  management at a specialist referral centre.
      • Help to decide who else should be informed of the diagnosis.
      • Advise on the need for contact tracing, partner notification and partner screening. Under the Infectious Diseases Act (IDA), a medical practitioner may disclose information relating to any person whom he reasonably believes to be infected with HIV/AIDS to the spouse, former spouse or other contact of the infected person, if:
        • He/she reasonably believes that it is medically appropriate and that there is a significant risk of infection to the partner;
        • He/she has counselled the infected person regarding the need to notify the partner and the medical practitioner reasonably believes that the infected person will not inform the partner; and
        • He/she has informed the infected person of his intent to make such disclosure to the partner.
      • Advise on the risk of infecting others through sexual activities, blood/organ donation, sharing injection needles etc and the need to take preventive measures at all times to prevent the transmission of HIV.
      • Inform the patient that it is an offence under the IDA for a HIV-infected person to carry out activities that could transmit HIV. It is also an offence under the IDA for a person with HIV/AIDS to engage in sex with another person unless prior to sex, he has informed that person of the risk of contracting HIV/AIDS from him and that person has voluntarily agreed to take that risk.

    • Being faithful to one uninfected partner.
    • Practise safer sex (correct and consistent condom use).
    • Avoid casual and commercial sex.
    • Avoid needle sharing.
    • At-risk people should not donate blood.
    • Donor assessment and screening of donated blood.
    • Screening of STI and TB patients.
    • Enhanced screening; e.g. opt-out testing in pregnant females and hospitalised patients.
    • Standard universal precautions for blood and body fluids.
    • No effective vaccination is available at present.


    1. The Body. (A patient informational website). Accessed Oct 2010.
    2. AIDSinfo: (A physician and patient informational website). Accessed Oct 2010.
    3. Huang XH, Chen MI, Ang LW et al. Seroprevalence of human immunodeficiency virus (HIV) among sentinel surveillance populations in Singapore, 1989-2008. Epidemiol News Bulletin 2009;35:63-8
    4. Lee CC, Sun YJ, Barkham T et al. Primary drug resistance and transmission analysis of HIV-1 in acute and recent drug-naïve seroconverters in Singapore. HIV Med. 2009 ;10:370-7
    5. US Centers for Disease Control and Prevention. Guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents. MMWR 2009; 58(RR-4): 1-207.

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