Everyone experiences HIV infection differently. However, as a general way of describing the disease process, the course of HIV infection can be looked at in four (4) stages. These stages are important because different treatment options may be considered at each stage.
The first stage of HIV infection is often called primary or acute infection. During acute HIV infection, the virus makes its way to the lymph nodes, a process which probably takes three to five days. In the lymph nodes, HIV reproduces or replicates very quickly and releases new virus into the bloodstream. This burst of rapid HIV replication usually lasts for two or three months.
Many people experience flu-like symptoms two to 12 weeks after they are first infected with HIV. These can include:
During primary infection, the amount of HIV in the body is very high and there is often a sharp drop in the number of CD4+ cells. People with acute infection usually do not test HIV positive because the body has not yet had time to produce antibodies against the virus. And it is this antibody that is detected in the standard tests to see if someone is HIV positive (see below).
During this time, the body begins to produce large numbers of CD8+ cells. These cells produce antiviral chemicals that help shut down or destroy virus-infected cells, thus helping to reduce the amount of virus in the blood (the viral load).
As the immune system learns to recognize and fight HIV, B cells start to make the HIV antibodies. When an HIV test is positive, that means that HIV antibodies have been found in the blood sample. Seroconversion means that someone's blood has changed or converted from being negative for HIV antibodies to being positive for HIV antibodies. Seroconversion usually happens one to three months after infection.
Asymptomatic means without symptoms. Many people with HIV may have few or no signs or symptoms of the disease for up to 10 years. However, some people may progress much faster, seeing their CD4+ cells decline within a few years and experiencing symptoms in the first few years after infection. And some lucky few, called long-term non-progressors, may continue to have normal CD4+ cell counts and no symptoms for much longer than the average.
Many factors have been found to affect the speed of disease progression, including the following:
a person's genes;
the strength of the virus with which someone is infected;
the type of immune response that is produced against the virus;
the nutrient level of the person both at the time of infection and later;
the person's mental state and stress level (and how well that stress is handled); and
various lifestyle factors such as smoking.
During the asymptomatic period, the only evidence of HIV infection may come from lab tests. Blood tests may show lower-than-normal numbers of CD4+ cells and moderate levels of HIV. The amount of HIV in the blood is usually called the viral load.
Although the immune system is able to fight HIV, it cannot get rid of the virus completely. Gradually, in most people the virus will be able to damage the immune system and they will progress to symptomatic infection.
As time passes, the damage to the immune system increases and the body's defenses weaken. At this stage, HIV may cause symptoms of long-term infection, such as chronic fatigue, weight loss, skin problems or diarrhea. This may occur when CD4+ cells are still at reasonable levels, or only after they have dropped to the stage officially called AIDS.
AIDS stands for Acquired ImmunoDeficiency Syndrome.
Acquired means that the condition is not inherited -- you acquire (get) it at some point in your life.
Immunodeficiency is a weakness in your immune system.
Syndrome is a combination of symptoms and/or diseases.
An official diagnosis of AIDS in Canada is given when a person with HIV develops one or more opportunistic infections or certain cancers.
A damaged immune system can leave HIV positive people vulnerable to infections that a healthy immune system could easily control. These infections are called "opportunistic" because they take the opportunity to cause disease when the immune system is weakened. Included among the opportunistic infections and other conditions that are considered "AIDS-defining" are:
bacterial infections -- such as Mycobacterium avium complex (MAC) or tuberculosis (TB)
fungal infections -- such as Candida overgrowth, cryptococcal meningitis or Pneumocystis carinii pneumonia (PCP)
parasitic infections -- such as cryptosporidiosis (crypto) or toxoplasmosis (toxo)
viral infections -- such as cytomegalovirus (CMV) or progressive multifocal leukoencephalopathy (PML)
cancers -- such as non-Hodgkin's lymphoma (NHL), Kaposi's sarcoma (KS), and anal and cervical cancer
A full list of AIDS-defining conditions can be found on the Web at:
Gay Men's Health Crisis (GMHC) -- list of AIDS-defining illnesses (in the "Treatment" section): www.gmhc.org/health/treatment.html
HIV Insite -- list of infections associated with HIV (in the "AIDS Knowledgebase" section): http://hivinsite.ucsf.edu/InSite.jsp?page=kb-05
The U.S. Centers for Disease Control and Prevention (CDC) -- 1993 Revised Classification System for HIV Infection and Expanded Surveillance Case Definition for AIDS among Adolescents and Adults (see Appendix B): www.cdc.gov/mmwr/preview/mmwrhtml/00018871.htm
For more information on specific opportunistic infections, check out CATIE's Fact Sheets at www.catie.ca/facts.nsf or by calling 1.800.263.1638 [if you're in Canada].