The Epidemic

 

GRADES: 6-12

 

TIME NEEDED: 30-45 minutes

 

An epidemic is defined by the American Heritage Dictionary as - "Spreading rapidly and extensively among individuals in an area. Said especially of contagious diseases. A contagious disease that spreads rapidly."

 

An epidemic may be non-communicable, that is, person to person contact does not spread disease. An example of this is food poisoning, which does not spread from one person to another. A communicable infection is spread from person to person. There are many possible routes of transmission

including:

 

1) respiratory - aerosol droplet, nose or mouth-to-hand or object-to-nose

2) salivary - direct transfer, kissing

3) gastrointestinal - stool-to-hand-to-food, object-to-mouth

4) blood - transfusion, needle prick, sharing needles, semen

 

In the lab today we will create an epidemic situation. One student in the lab will be "infected". The "disease" can be spread through handshaking. Each student will shake hands with a limited number of students and keep track of each contact and the order of the contact. The determination of whether you have the "disease" will be made by observing what grows on a petri dish.

 

Materials Needed Per Student

 

gloves

set of colored cards with the same number on each card

1 tryptic soy agar plate (2 if you are numbers 5, 10, 15, 20, 25, 30...)

a sterile swab (2 if you are numbers 5, 10, 15, 20, 25, 30 …)

*a petri dish with a moist piece of gauze (moisten gauze with 0.9% sterile NaCl)

(* NOTE: 1 student in the group will have their gauze moistened with a liquid culture of serratia marcescens bacteria. Only the instructor should know who this student is.)

 

Experimental Procedure

 

Day 1:

 

(instructor should announce each step so that students are all following the steps at the same time)

 

  1. 1. Write your initials on the bottom of the agar plate. Persons with 2 plates should label their plates #1 and #2.
  2. 2. Place your gloves on.
  3. 3. Remove the gauze with your LEFT hand and rub it onto your RIGHT hand, in particular the areas where you make contact when shaking hands.
  4. 4. Remove your LEFT hand glove and dispose of it. DO NOT TOUCH ANYTHING WITH YOUR RIGHT HAND!
  5. 5. Pick up your cards with your LEFT hand and walk around the lab to another classmate. DO NOT TOUCH THE OTHER CLASSMATE YET!!
  6. On the instructors command, shake hands with the other classmate . Make sure you really come in contact with the innoculated area of the glove. After shaking hands, exchange a RED card with that person. DO NOT SHAKE ANYONE ELSES HAND YET!!
  7. Walk over to another different classmate, and when the instructor says it is OK, shake that persons hand. Give that person your ORANGE card, and take their ORANGE card. DO NOT SHAKE ANYONE ELSES HAND YET!!
  8. If you are number 5, 10, 15, 20, 25, 30 or 35 you will need to take a sample of your hand at this point. (Other students will need to wait, and not touch anything) Sample your hand as follows:

    Carefully remove a sterile swab from the wrapper. Rub your RIGHT hand, all over the palm and fingers, with the sterile swab and then rub the swab gently over the agar surface of your agar plate labeled #1.

    Walk over to another different classmate, and when the instructor says it is OK, shake that persons hand. Give that person your YELLOW card, and take their YELLOW card
    DO NOT SHAKE ANYONE ELSES HAND YET!!

  9. Walk over to another different classmate, and when the instructor says it is OK, shake that persons hand. Give that person your GREEN  card, and take their GREEN card. DO NOT SHAKE ANYONE ELSES HAND YET!!
  10. 10. Walk over to another different classmate, and when the instructor says it is OK, shake that persons hand. Give that person your BLUE card, and take their BLUE card. You should now have 5 colored cards, each with a different persons number on it. DO NOT SHAKE ANYONE ELSES HAND!!
  11. After 4 shakes, everyone will sample their s hand with a sterile swab, and then rub the swab gently over the surface of the agar plate. (Plate #2 for persons 5, 10, 15, and 20). Your instructor will store your plates in the incubator until tomorrow.
  12. Remove your glove and dispose of it. Write down, in the table below, your "contact history" (who you shook hands with, and in which order).

 

CONTACT HISTORY

shake # color card number on card

 

1 red

2 orange

3 yellow

4 green

5 blue

 

Day 2:

 

1. Record your contact history on the blackboard.

2. Observe your agar plates for sign of bacterial growth. Determine if you were infected, and then add this information to the blackboard chart.

3. After all of the data has been reported, attempt to determine who was the initially infected student. If you cant figure out who that was, explain why.

 

person # red orange yellow green blue + or - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40