Why is it so difficult to find a cure for the AIDS virus? How does the human immune system work? How is AIDS transmitted?

What is acquired immune deficiency syndrome?
David takes a journey into the human body to learn about the immune system.
Segment length: 9:35


The world has now entered the second decade of dealing with acquired immune deficiency syndrome (AIDS). According to the Centers for Disease Control, the AIDS virus was first named in 1982, and the human immunodeficiency virus (HIV) was identified in 1984. It is important to make the distinction between the two acronyms, AIDS and HIV: Once infected by the HIV virus, a person may not develop the disease AIDS for years. The incubation period for developing AIDS varies from one year to 10, though experts disagree on this.

The segment shows what happens in a normal immune system versus an immune system infected with HIV. Under normal conditions, disease-causing agents (pathogens) attempt to invade the body, inducing an immune response from T-cells, B-cells, and macrophages . T-cells process the foreign body so that it can be recognized by the B-cells, which in turn produce antibodies that grab the pathogens, pin them down, and mark them for destruction by the macrophages. More and more defenders descend upon the attacking virus until the invasion is neutralized.

HIV acts differently than most pathogens: It seeks out the T-cells and incorporates itself into them. Then HIV either reproduces so quickly that it destroys the host cell, or it causes the genetic machinery to reproduce copies of itself, so that it can send out more virus particles to attack other T-cells. HIV doesn't always act quickly; it can hide out in the body and not reproduce immediately. But once in the body, HIV stays there forever, using the host cell as an HIV "factory."

Eventually, the body's supply of T-cells becomes depleted until the immune-defense system is severely weakened and susceptible to infection by "opportunistic" pathogens, such as Pneumocystis carinii, a serious respiratory infection, and malignant growths like Kaposi's sarcoma, a vascular-type cancer.

HIV is transmitted from an infected person to a healthy person in three basic ways: through sexual intercourse, through the blood system by sharing needles, and perinatally from mother to child. In the United States, the first decade of HIV infection occurred primarily among intravenous-drug abusers, people who had received blood transfusions, homosexual men, bisexual men, and all of their sexual partners. In this second decade, "heterosexual transmission will become the predominant mode of HIV transmission throughout the world," according to the World Health Organization.


What do people fear most about AIDS? Why is there such confusion about AIDS? Does the AIDS epidemic resemble others in our past (e.g., Hansen's disease, tuberculosis, polio)? Have other diseases generated as much fear and loathing?


B-cells a group of lymphocytes (white blood cells) that helps the body manufacture antibodies, or actually manufactures the antibodies themselves
macrophages "scavenger" cells in the immune system that engulf and destroy an invading virus
pathogens specific organisms (that may be cellular) with biological, chemical, or thermal agents that cause disease
T-cells a group of lymphocytes (white blood cells) that control and regulate the immune-defense system


Collier, D.M. (1992) "AIDS." In The new book of popular science 5: 417-420 New York: Grolier.

Cox, F.D. (1992) The AIDS booklet. New York: William C. Brown.

Nourse, A.E. (1990) Teen guide to AIDS prevention. New York: Franklin Watts.

Saving a generation. (1991) Washington, DC: State of the Art. Videotape.

Additional sources of information:

American Red Cross
AIDS Education Office
2025 E Street NW
Washington, DC 20006
(202) 728-6554 or 6531

Centers for Disease Control (CDC)
1600 Clifton Road NE
Atlanta, GA 30333

CDC National AIDS hotline
(800) 342-AIDS

CDC Spanish hotline
(800) 344-SIDA

CDC Hearing-impaired hotline
(800) AIDS-TTY

Main Activity

Let's Play Cards
Find out how HIV is transmitted, and perhaps more importantly, how it is not transmitted.

A great deal of myth and mistaken information surrounds the subject of how people become infected with HIV. To clarify the specific ways that HIV is transmitted and to dispel some of the myths, create a card game.


  1. On one card, print an actual or plausible risk factor associated with the transmission of HIV. On the next card, print an unlikely or implausible risk factor. Continue until you have as many cards as you wish. Put the cards in the box.
  2. Have each student pick a card from the box, read it aloud, and place it in one of two piles or mount it on a bulletin board using these two headings:
    Risk Factor and Not a Risk Factor

Examples of risk factors: sharing needles with anyone; mixing of blood between persons (as in some rituals of scraping the skin to mingle blood); sexual intercourse; medical situations involving blood when no barrier precautions have been taken; being born to a mother who has HIV/AIDS; tattoo shops (if needles are reused); acupuncture (if needles are reused)

Examples of activities that are not likely to be risk factors: cat bites; sharing food with a person infected with HIV/AIDS; eating food handled, prepared, or served by someone infected with HIV/AIDS; being coughed on; mosquito bites; bites from lice, flies, and other insects; swimming pools; toilet seats; wet towels; sweat; saliva or tears (Saliva and tears have the virus present, but it appears to break down and there have been no known cases.); urine; crowded elevators; hugging; shaking hands; laundromats; clothing; telephones; drinking glasses; eating utensils; giving blood; receiving a blood transfusion (Current screening procedures make blood transfusions almost risk-free.)


1. Have any of these issues regarding the transmission of HIV/AIDS appeared in the news?

2. How do misconceptions about the contagiousness of AIDS or any other disease get started? Is fear about contagion in general necessarily negative? What problems could be caused by misunderstanding the contagion factor of AIDS?

Work with a language arts or social studies teacher in your school to stage a debate about AIDS and education. Some possible topics include: Should communities provide free needles and condoms to high-risk populations? Should doctors and dentists be required to be tested for HIV/AIDS? Could there ever be a reason at your school to have students screened for the virus? Do condoms make sex safe, or safer?

The Centers for Disease Control (CDC) has published a list of recommended precautions to be used by health-care professionals with their patients. Invite a health-care professional who understands and uses the precautions on the job to demonstrate and discuss them in your classroom. Ask the health-care provider what he or she feels is the greatest risk when dealing with any patient. Is he frightened about catching the virus? Has she ever treated someone with the virus? Stress that the precautions work both ways--protecting both patient and health-care professional alike.

Create an advertising campaign aimed at persuading young people to protect themselves against infection by HIV. Divide the class into groups and have each group aim its advertising at one of these target audiences: grades kindergarten through 3rd, 4th through 8th, and 9th through 12th. Plan radio and television spots, as well as print materials, including posters, articles in the school newspapers, and public service announcements. Work with a language arts teacher on the finer points of persuasion.

There currently are several HIV vaccines being tested. The most common vaccines available today consist of doses of the pathogen so mild they cannot cause the disease itself, but strong enough to bring on an immune reaction in the body. Study some of the diseases for which vaccines have been developed: smallpox; yellow fever; rabies; influenza; polio; malaria; measles; mumps; rubella; diphtheria; and tetanus.

Tapes of this episode of Newton's Apple and others are available from GPN for only $24.95.
Please call 1-800-228-4630.
For information on other Newton's Apple resources for home and school,
please call 1-800-588-NEWTON!

We encourage duplication for educational
non-commercial use!

Newton's Apple is a production of KTCA Twin Cities Public Television.
Made possible by a grant from 3M.
Educational materials developed with the National Science Teachers Association.

PBS Online - Minnesota Online - Welcome to Newton's Apple - Teacher's Guides Index