Infection! Epidemic Simulation
Super Value Laboratory Kit
Materials Included In Kit
Sodium hydroxide solution, 0.1 M, 75 mL
Thymol blue indicator solution, 0.04%, 75 mL
Culture tubes, 20 x 150 mm, 35
Pipets, disposable, graduated, 160
Additional Materials Required
Water, distilled or deionized†
Erlenmeyer flask, 1-L†
Graduated cylinder, 10-mL†
Pen or pencil*
Test tube racks*
White board or overhead†
*for each student
†for Prelab Preparation
- Dilute the 0.1 M sodium hydroxide solution to 0.001 M:.
- Fill a 1-L Erlenmeyer flask about half full with distilled or deionized water.
- Measure 7 ml of the 0.1 M sodium hydroxide solution in a graduated cylinder. Add 7 mL of sodium hydroxide to the Erlenmeyer flask.
- Fill the Erlenmeyer flask to 700 mL with deionized water and mix well.
- Number each test tube in sequential order.
- Prepare the test tubes by filling all but one of the tubes required approximately one-half full with distilled or deionized water. This is about 20 mL of deionized water in each tube.
- Fill the remaining tube (“the carrier”) to the same level as the other tubes with the 0.001 M sodium hydroxide solution. The carrier tube should appear exactly as the remaining tubes and be randomly placed among them in the test tube rack. Record the number of the “carrier” tube.
- Set up a result grid on the white board or on an overhead. It will appear similar to the following chart. Write in the test tube numbers in sequential order in the first column.
Dilute sodium hydroxide solutions are skin and eye irritants. Thymol blue will stain skin and clothing. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Use forceps to retrieve any pipets that fall into the test tubes. Do not tip the test tube. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The resulting solutions may be disposed of down the drain with excess water following Flinn Suggested Disposal Method #26b.
- Enough materials are provided in this kit for five classes of 30 students. This laboratory activity can reasonably be completed in one 50-minute class period.
- Participants should be cautioned at the outset to exchange fluids carefully to avoid spillage. Spills should be absorbed on damp paper towels immediately. It is also possible for the pipet to fall into the test tube, in which case the student should not attempt to retrieve it with bare fingers or by tipping the tube. The instructor should retrieve pipets either with forceps or with gloved fingers. At no time should pipets be used by participants to “squirt” each other. The possibility of eye contact with dilute sodium hydroxide should be strictly avoided.
- It may be necessary to use a 0.01 M sodium hydroxide solution if more than 4 exchanges are used.
- The number of exchanges each participant conducts and the number of tubes initially “infected” will determine the ultimate rate of “infection.” For class sizes of 30 or less, one carrier should provide a dramatic result. The instructor should direct a minimum of two exchanges per participant for smaller classes but no more than four for up to 35 participants. It is important that participants circulate throughout the room or between groups following each exchange—this will ensure that the same few people do not simply keep re-infecting each other. When repeating the exercise, the instructor may wish to vary the number of exchanges, the number of initial carriers, or even to instruct one or more participants to “abstain” from exchanging.
- Thymol blue is a pH indicator. It is blue at pH levels of 9.8 or greater, yellow at pH levels between 8 and 2.8, and red at pH levels below 1.2. Check the pH of the deionized water before beginning. Deionized water is often slightly acidic due to carboxylic acid formed when the water is exposed to the carbon dioxide in air. The pH of the deionized water used to test this procedure was 5.5. Six exchanges from the original tube of 0.001 M sodium hydroxide still resulted in a positive-blue result.
- Tracking the original host is the most challenging aspect of the lab, especially when more than two exchanges occur. If students have a difficult time working from the result to the original host, have them work from the host forward to track who infected whom.
- Although the Background section focuses on EBV, the same activity can be used to focus on sexually transmitted pathogens, such as HIV.
- Extend the learning by assigning pathogens to be researched to students. Have them create a mini-lesson or poster with information (e.g., type of pathogen, method of infection, vaccines or treatments).
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering Practices
Analyzing and interpreting data
Constructing explanations and designing solutions
Obtaining, evaluation, and communicating information
Developing and using models
Disciplinary Core Ideas
MS-LS1.A: Structure and Function
HS-LS2.A: Interdependent Relationships in Ecosystems
HS-LS2.C: Ecosystem Dynamics, Functioning, and Resilience
Cause and effect
Structure and function
MS-LS2-2: Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.
HS-LS2-6: Evaluate claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.
HS-LS2-8: Evaluate evidence for the role of group behavior on individual and species’ chances to survive and reproduce
Answers to Prelab Questions
- Read the Safety Precautions section. Why is it important to protect skin and eyes from the liquid used in this lab activity?
The solutions used are skin and eye irritants and will stain skin and clothing.
- Of the diseases listed in the Introduction and Background sections, only one has a vaccine associated with it. Using other reference sources, such as your textbook or an Internet site like www.nih.gov, research which disease has a vaccine and how vaccines work to protect against the disease.
Mumps is the only disease listed that currently has a vaccine. The mumps vaccine is a live, attenuated vaccine. The vaccine is injected into the body where the person’s immune system is able to react to the weakened virus and to create immunity to the virus should it ever enter the vaccinated person.
Answers to Questions
- Determine which test tube initially contained the simulated saliva and record your choice below.
Student answers will vary. In the example above it is test tube 1.
- Describe how you determined your choice.
Student answers will vary but should include a discussion of the test result color and tracking the color. The best way to determine the initial test tube if you need to help is to cross out the numbers of those tubes that tested yellow. Then look for a pattern. In the example above, tube 20 tested blue but it exchanged with tubes 6 and 18 which remained yellow. Consequently it was the last tube, number 1, that caused 20 to be blue. Work backwards if possible. This demonstrates how difficult tracking the source can be. If need be, give the students the number of the initial tube, in our example tube 1, and let them work it forward.
- As a class, reach a consensus on which test tube initially contained the simulated saliva. Did the majority of the class agree with your initial choice?
Student answers will vary.
- Epidemiologists are scientists who try to determine the cause of an outbreak of disease. Besides laboratory test results, epidemiologists often interview the patient and family members. Hypothesize why interviews are important in tracking the initial host for a disease outbreak.
The actual pathogen will help narrow how it was transmitted but does not allow the epidemiologist to determine exactly who (or what) is responsible for the outbreak of disease. Patient interviews regarding where they’ve been, what they’ve eaten, and so on will help narrow the potential host further. Once the choices have been narrowed down to a few possibilities, the epidemiologist can request tests to confirm the host.
Centers for Disease Control and Prevention. About Epstein-Barr Virus (EBV). http://www.cdc.gov/epstein-barr/about-ebv.html. (accessed April 2014)
Understanding Vaccines. NIH Publication No. 08-4219, National Institute of Allergy and Infectious Diseases (NIAID). Updated January 2008. http://www.niaid.nih.gov/topics/vaccines/documents/undvacc.pdf (accessed April 2014)