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What is HIV?

Human Immunodeficiency Virus (HIV) is the virus that causes Acquired Immunodeficiency Syndrome (AIDS).¹ A virus is a microorganism that can survive and reproduce only with the help living cells.² HIV infects human immune system cells, using their energy and nutrients to produce more virus and spread throughout the body, ultimately destroying the immune system rendering an infected individual susceptible to life-threatening infections and rare cancers.^1,2

What is AIDS?

HIV becomes AIDS when the body’s immune system breaks down and is unable to fight off infections.¹ The clinical diagnosis of AIDS is:¹

1. A positive test for HIV and
2. One or both of the following
1. The presence of one or more AIDS-related infections or illnesses
2. A CD4 count that has reached or fallen bellow 200 cells per mL³ of blood. This is also known as the T-cell count. In healthy people the CD4 count ranges from 450 to 1200 cells/mL³

How is HIV transmitted?

HIV is found in certain bodily fluids of infected individuals, including blood, semen, vaginal secretions, and breast milk. The virus can be transmitted only if HIV-infected fluids enter the blood stream of another person. Such transmission is believed to occur through:¹

1. The lining of the vagina, rectum, mouth, and the opening at the tip of the penis
2. Intravenous injection with a syringe
3. A break in the skin (eg, a cut or sore)

Common methods of transmission include:¹

1. Unprotected sexual intercourse (both vaginal and anal)
2. Unprotected oral sex
3. Sharing needles or syringes
4. Mother-to-infant transmission during pregnancy, childbirth, or breast feeding

How does HIV affect the body?

The human immune system comprises cells, tissues, and organs that work together to defend the body against foreign invaders, including viruses.² HIV primarily infects white blood cells, which are principal players in the human immune system that protect the body from disease.¹ There are many types of white blood cells, including Helper T cells, Suppressor T cells, Cytotoxic T cells, and B cells.³ As HIV multiplies, there is a progressive loss of Helper T cells. Helper T cells are also called CD4 cells. This reduction in CD4 cells weakens the entire immune system, leaving the infected person open to opportunistic infections and illnesses such as pneumonia and cancer.¹

References:

1. American Foundation for AIDS Research (amfAR). About HIV/AIDS. Available at: http://www.amfar.org/cgi-bin/iowa/abouthiv/record.html?record=7. Accessed August 2007.
2. National Institutes of Health. Understanding the immune system: how it works. Available at: http://www.niaid.nih.gov/publications/ immune /the_ immune _ system .pdf . Accessed August. 2007.
3. The Body. Understanding the immune system. Available at: http://www.thebody.com/content/art6319.html. Accessed August 2007.