This project is sponsored by the AIDS Trust Fund.
What are HIV and AIDS?
Human immunodeficiency virus (HIV) damages the immune system of a person, whose disease-fighting cells (CD4) are progressively destroyed. Acquired Immunodeficiency Syndrome, also known as AIDS, is the late stage of HIV infection. The progression to acquired immunodeficiency syndrome (AIDS) is confirmed when the CD4 cell count drops to a critical level and/or the person develops infections or infection-related cancers that usually do not manifest in a healthy body. There are two strains of HIV virus: HIV-1 and HIV-2. HIV-1 is globally distributed whereas HIV-2 is mostly found in African countries.
A HIV disease can be categorized into three stages: acute infection, clinical latency, and finally AIDS. It is important to note that HIV is transmissible at all stages.
Acute infection
Many people experience one or more flu-like symptoms within 2-4 weeks after contracting HIV. This is called acute retroviral syndrome (ARS). Some people will be asymptomatic during this period. The amount of HIV will rapidly increase in your body, making you at high risk of transmitting the disease. A large amount of CD4 cells will be destroyed. Initiation of antiretroviral therapy (ART), an approved treatment for HIV infection, at this stage is most desirable.
Clinical latency
The clinical latency period is that the virus is latent in the body, and yet active. The reproduction of the virus is so low that the infected person may be asymptomatic or have mild symptoms. This clinical latency period may last up to a few decades in ART-treated patients or up to a decade in untreated patients. The disease is still transmissible to another person, although the risk is greatly reduced with ART.
aids
The disease is considered to have progressed to AIDS when the CD4 cell level drops to a critically low level (< 200 cells per cubic millimeter of blood) and an opportunistic illness develops. That means the immune system has become too weak to protect you. Unlike the international classification which defines AIDS based on a low CD4 cell count, the Hong Kong HIV Surveillance Office also requires the presence of an opportunistic illness in the case definition (i.e., AIDS-indicating condition).
HIV Transmission
Human Immunodeficiency Virus (HIV) is an infectious disease that attacks the immune system. The most common route of HIV transmission is having unprotected sex and sharing needles, syringes, and other injection equipment with an HIV-infected person. You are at risk of getting HIV if you do not use condoms with a partner whose HIV status is positive or unknown and share used needles with an infected drug user.
Mother-child transmission is less common as HIV testing is now available for pregnant women. HIV can be passed from the mother to the infant during pregnancy, delivery and breastfeeding. The risk of transmission is reduced when the infected woman takes medications during pregnancy. HIV can also be spread, though uncommon nowadays, by these routes:
- Injured by a HIV-contaminated needle stick or sharp (especially for health care workers)
- Receiving blood transfusions, blood products, or organ/tissue transplants that are contaminated with HIV
Some body fluids – blood, semen, pre-seminal fluid (pre-cum), rectal fluids, vaginal fluids, and breast milk – carrying HIV from one person can transmit to others. Transmission only occurs when these body fluids come in contact with mucous membrane (such as the mouth, the rectum, genital areas, etc) or damaged tissue or are directly injected into the bloodstream. Therefore, HIV infection can take place even the person has no broken skin and no direct contact with HIV-contaminated blood. HIV is not transmitted through some other body fluids, including saliva, sweat, tears, feces, urine, vomit and nasal fluid.
Signs and symptoms
Primary HIV infection |
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Clinical latency |
By the end of the clinical latency period, the virus levels increase and lead to more severe symptoms:
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AIDS |
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