STS Biology: Teaching Controversial Topics - Viruses Unit
Viruses Unit, including: Smallpox Lesson, Chain of Transmission
(modified by Randall Good from Rita Wilson, San Bernardino Co. Fire Dept.)
and Fluid Exchange Activity (modified by Randall Good from a version of
the activity by Mike Goff, Ayala High School, Chino Hills, CA).
Type of Entry:
- Unit Outline w/lesson/class activities
Type of Activity:
- hands on activity
- inquiry lab
- group/cooperative learning
The fluid exchange activity is designed to simulate the uncontrolled spread of a disease through a population. It is best when combined with a unit about viruses. Test tubes are prepared with distilled water, except 1 or 2 (depending on class size) which contain a dilute (0.1M) solution of NaOH. Tubes are randomly distributed throughout the class so that each student receives one. Students are then asked to move about the room for 5 minutes, using pipettes/droppers to exchange fluids with at least 3 people. Students are advised not to spill any of the liquid. Droppers are collected in a large beaker or container, and students return to desks while holding tubes. The students are then informed that they were simulating the type of fluid exchange that occurs when iv needles are shared, or when people engage in unprotected sex. Students are also informed that one of the test tubes has been contaminated with a simulated "disease." What follows is a test to determine who has been "infected," and an epidemiological study to locate "patient zero."
This lesson helps students to answer the following questions:
- What are some of the reasons that Native Americans died of disease when European explorers came to the Americas?
- What is the nature of active and conferred immunity?
- What are some of the most dangerous viruses known to mankind, and how do they spread?
Notes For the Teacher: There is a great deal of sensationalism circulating through the mass media about so called "killer viruses." You can access students' natural curiosity about this subject--even Life Science students watch TV and see news reports about Ebola, HIV, and others. A scientific approach to the study of these diseases can yield tremendous learning opportunities, and help to clear up the superstitions and misinformation about viruses and the diseases they cause.
You Will Need:
- invitation to learn:
- a microbiology text with pictures,
- someone with a smallpox immunization scar (you, if you're old enough),
- video on disease (CBS aired a good program available on video-48 Hours: "In the Danger Zone" Aired in 1993. There are now many more reports available. PBS, Nova: "Virus Hunters" is also quite good (last aired 1996). Call VideoFinders for PBS videos (800)343-4727
- Table of population statistics (provided in lesson, later) and graph paper
- Materials for Fluid Exchange Activity (described later)
- Poster paper, white board, or chalk board for display of epidemiology.
- Need basic graph making ability (or this can become a sidelight of the lesson)
- Complete a worksheet on Smallpox, and Chain of
Transmission for Smallpox, HIV, Cold, and Ebola as examples of viruses.
- Participate in a 5-minute fluid exchange using test-tubes and pipettes
- Be asked to create from memory a list of those with whom they traded fluids. This will begin the epidemiological study.
- Life Science students will be led by teacher in the epidemiological study, while Biology students should manage their own study.
Preparation Time needed:
- Time to preview video or other similar resource (varies depending on prior teacher knowledge)
- Time to prepare fluid exchange: Test tubes should be prepared in advance, if you have enough materials. One dropper and test tube is required per student. If not enough supplies are available, then passing time can be spent cleaning and refilling test tubes.
Class Time Needed: At least 1 week is recommended.
- Video: 1 class period
- Smallpox Lesson: 1 class period for graph and checking for understanding, 1 more class period for conclusions (NOTE: for students who do homework, the conclusion or graph can be assigned at home, but some discussion must occur in class)
- Fluid Exchange activity: 1 class period for exchange and epidemiology and discussion.
- Chain of Transmission: 1/2 class period per disease discussed.
- Assessment: Quiz (optional) at the end of the lesson
- Invitation about viruses (I have used pictures from textbooks, immunization scar on my arm, and videotapes)--CBS/FOX1s 48 Hours: "In the Danger Zone," 1993, is particularly good, as is Nova: 3The Virus Hunters2 (PBS videos can be located with VideoFinders, 1(800)343-4727.
- Smallpox Lesson: Population chart of Native Mexicans, 1600-1700
- Graph Paper and Rulers
- Fluid Exchange activity Materials:
- Test Tubes (1 per student per class is most successful, at least class set)
- Long Droppers, Pipettes, etc. A drinking straw can be converted
(VanCleave, 1993). 1 per student.
- Solution of Phenolphthaleine pH indicator (about 20 mL per class).
- Large beaker or jar to collect used pipettes, racks for test tubes.
- Chain of Transmission transparency or Handout
- Video: Depending on the video used, a variety of worksheets or notes can be created or adapted.
- Smallpox Lesson: Students are given a chart showing the population change of Native Mexicans (Aztecs) over a period of about 100 years. Students are to interpret the graph using the attached questions. (enclosed)
Next, students are given a series of connected "facts" from a Fact Sheet on smallpox. They are to offer an explanation as to why so many Native Americans died of a disease that Europeans were carrying. The answer is that the Americans did not have an immunity to the disease because they had not domesticated cattle. Europeans had cattle, and had all either died or obtained immunity to smallpox. Some, however, were carrying the disease to the new world. This should lead into a discussion of the Chain of Transmission.
- Chain of Transmission: (adapted by Randall Good from Rita Wilson's Blood-borne pathogens class, San Bernardino County Fire Dept/ICEMA)
Using the enclosed diagram, students should be told that a disease spreads only if certain conditions are met. These conditions can be likened to links in a chain, where the chain represents spread of disease. If a disease is to be stopped, one of the links must be broken. As time permits, students should try to fill in Chain of transmission analyses for several viruses: HIV, Cold, Ebola, Smallpox. This could become a mini research project, in which students access WHO (World Health Organization) data off the internet, etc.
Fluid Exchange Activity (adapted by Randall Good from a lesson given by Mike Goff, Ayala High School, Chino Hills, CA)
The fluid exchange activity is designed to simulate the uncontrolled spread of a disease through a population. It is best when combined with a unit about viruses. Test tubes are prepared with distilled water, except 1 or 2 (depending on class size) which contains a dilute (0.1M) solution of NaOH. Tubes are randomly distributed throughout the class so that each student receives one. It is sometimes helpful to save the "contaminated tube" and slip it to a student who you know will exchange fluids with many students. In any case, you should keep track of who you give the contaminated tube to, so that you can help guide the epidemiological study.
Students are then asked to move about the room for 5 minutes, using pipettes/droppers to exchange fluids with at least 3 people. Before exchanging, it may be useful to pull 1 or 2 students aside and ask them not to trade fluids with anyone else, no matter what. This can be used later to stress the role of abstinence in the prevention of sexually transmitted diseases. Students are advised not to spill any of the liquid. After 5 minutes, droppers are collected in a large beaker or container, and students return to desks while holding tubes. Care must be taken to insure that no liquid is spilled. NaOH is caustic, and can irritate skin and eyes. Aprons and goggles should be used if available.
The students are then informed that they were simulating the type of fluid exchange that occurs when iv needles are shared, or when people engage in unprotected sex. Students are also informed that one of the test tubes has been contaminated with a simulated "disease." Students are to report for mandatory "testing." What follows is a test to determine who has been "infected," in which students line up and have pH indicator added to their test tubes. A pink color (bright or faint) indicates a positive result; the student is "infected." After all testing is completed, students return their tubes to racks, and fill out the survey.
Students are to complete and an epidemiological study to locate "patient zero." This will be accomplished by their compilation of data based on memories of who they traded with. This is not unlike the work that real epidemiologists do; their work is often only as reliable as the memories of the patients with whom they work! The search for patient zero is facilitated by the teacher in a Life Science class; in Biology, students run the study. Breakthroughs in this seemingly overwhelming study occur when a student realizes that they exchanged fluids with someone who tested positive, but they themselves were not positive. This usually indicates that the student who tested positive was not the original carrier, because there was one point in time during the exchange period that they were negative or "clear." Usually, it becomes clear that there are 1 or 2 students that tested positive, and that everyone they traded with also tested positive. These are usually the original carriers.
It is usually quite useful and powerful message to pull a student aside before fluid exchange occurs and ask them to not trade with anybody. Make sure this is not the one who has the contaminated tube. If this person follows instructions, then it can be pointed out during discussion that he/she remained uninfected because they did not exchange fluids.
Method of Assessment/Evaluation
Assessment: Assessment will occur in several forms: Checking for understanding during all discussions, and listening to the types of questions students ask will indicate how the class is doing. However, concrete assessments should include, but are not limited to:
- Smallpox: Grade their hypotheses about how so many Native Americans died using this following rubric:
Reasoning Poor Reasoning Average Reasoning Superior
5 7 10
- Chain of Transmission: I always give a traditional quiz on this part; I want the students to know the portals of entry and methods of transmission of HIV. Portals are (mouth, anus, genitals, break in skin). Body fluids which carry the highest levels of virus include semen, vaginal fluids, and blood. Other body fluids, including breast milk, also carry the virus although in lower concentrations. Mini research projects can also be used to assess understanding.
- Fluid Exchange Activity: Assessment will occur through evaluation of the epidemiological study. I have found it most useful to complete the study as a whole class. Finding patient zero, or coming up with a few "most likely patient zeros" using sound science and logic should indicate successful lesson. I usually do not assign credit for this activity, in that it helps solidify concepts that are assessed using the above mentioned methods. Students usually are satisfied with the participation only.
An interesting video to watch (I recommend that the teacher watch, if not the class) is "And the Band Played On" by HBO video productions. It is available in most video stores, and chronicles the events in the early 1980's leading to the discovery of the virus that causes AIDS. If students are interested in epidemiology, this video demonstrates that process very well.
Also, many students will tell you they have seen the movie "Outbreak." You may wish to assign extra credit for students to watch this movie (get parent permission, it is rated "R" for language and subject matter), and analyze the science presented in the picture. Students could look for flaws and truths.