HIV (Human Immunodeficiency Virus) is a virus that attacks the immune system. There are two types of HIV: HIV-1 and HIV-2. HIV-1 is more virulent and more infectious than HIV-2.
HIV can infect a variety of immune cells such as T-helper/CD4 cells, macrophages, and microglial cells. As HIV infects and destroys more CD4 cells and makes more copies of itself, it gradually breaks down a person’s immune system. Even though there is currently no cure for HIV, with the right treatment and support, people affected by HIV have the possibility to live long and healthy lives. If HIV is left untreated, it may take up to 10 or 15 years for the immune system to be severely damaged.
The World Health Organisation (WHO) uses the following categories to classify the stages of the disease:
- Primary HIV infection: It can be asymptomatic or associated with acute retroviral syndrome.
- Stage I: HIV infection is asymptomatic. CD4 count is greater than 500/µl of blood.
- Stage II: Mild symptoms. A CD4 count of less than 500/µl.
- Stage III: Advanced symptoms. CD4 count of less than 350/µl.
- Stage IV or AIDS: Severe symptoms. CD4 count of less than 200/µl.
What is AIDS?
AIDS (Acquired Immune Deficiency Syndrome) is a set of symptoms caused by the progression of the HIV infection. A person affected by AIDS is characterised by a very weak immune system which is not able to fight off infections anymore. This is the last stage of HIV, when the infection is advanced, and if left untreated will lead to death.