Tracing an Epidemic

Davidson Students Volunteer for Science

8th Grade – Lab 2

Introduction• Bacteria, viruses, protists, and prions cause

diseases.– Strep throat, tuberculosis are caused by bacteria– AIDS, measles, chicken pox, mononucleosis– Malaria– Mad Cow’s Disease

• Epidemic vs. Pandemic– Pandemic affects larger, global population

• Spread of epidemic– Airborne– Waterborne– Exchange of body fluids

• Positive and Negative samples– Positive has disease-organism, Negative does not

• Indicator

Background Info

Background Info

Pre-Lesson SetupFor Demo #III:

1. Match up the eight numbered

cups with the numbered bottles.

• Make sure bottle C-8 is emptied

into cup 8 (0.025 M NaOH).

For Demo #IV:

• Fill one cup about half-full of

water for each student.

• For Patient 0 (DSVS member),

empty 1oz bottle of NaOH in

another 3.5 oz cup.

Demo #III: Testing For a Disease

1. Add “contaminated” liquid and clean liquid to two different 6 oz. cups.

2. Add four drops of indicator phenolphthalein to each cup.

• Pink – INFECTED; basic (sodium hydroxide)

• Clear – NOT INFECTED

Exp #IV: How Does A Disease Spread?

1. Need six volunteers. Two DSVS members will also participate. Write the exchange sequence chart on the board.

2. Pass out the numbered cups. – Cup #8 goes to DSVS member.

3. Follow Exchange Sequence Chart and exchange with partners. In “Exchange,” pour all of one cup into the second cup. Then pour half of the total liquid back into the first cup.

4. Inform the students that #8 was infected. Predict who else is infected.

5. Add a few drops of the indicator (phenolphthalein) to ALL the cups. The solution in cup #8 will turn pink.

6. Continue 2nd round of exchanges.

Number of infected doubles with each exchange. Ask how many exchanges would infect a classroom of 30 (5 exchanges)

Exchange Sequence #1 Exchange Sequence #2

Volunteer 1 Volunteer 5 Volunteer 1 Volunteer 2

Volunteer 2 Volunteer 6 Volunteer 3 Volunteer 4

Volunteer 3 Volunteer 7 Volunteer 5 Volunteer 6

Volunteer 4 Volunteer 8 Volunteer 7 Volunteer 8

Exp #V. The Disease Spreads • Pass out prepared cups half-

filled with water and empty 1 oz. cup to each student.

• Tell students to set aside a small amount of liquid in a separate cup as “uncontaminated” control.

• Write their names on the top line of their observation sheet. Write name of “exchange” partner.

• In “Exchange,” pour all of one cup into the second cup. Then pour half of the liquid back into the first cup.

• Continue 3 rounds of “exchange.”

Exp #VI. Identifying Patient Zero1. Test liquid by adding several drops of

indicator, phenolphthalein. 2. Ask all students to stand up.3. Ask all participants with an uninfected

(clear color) sample to sit down. Ask all infected participants (pink solutions) to bring their observation sheets and come to the front of the class.

4. Ask the group at the front of the class to look around and see if they exchanged with anyone in the group in the FIRST exchange. If they did not, then they should sit down.

5. Only two participants should be standing. One of these participants is patient zero.

6. Ask these participants to bring their the original uncontaminated liquid to the front of the room.

7. Add the indicator to the liquid in each of these 1 oz cups. The one that turns pink identifies patient zero.

Optional #VII: Tracing the Spread

• Ask the carriers to stand. Ask who exchanged with them during the first round.

• Ask those who exchanged with the people standing in the second round to stand.

• Ask those who exchanged with the people standing in the third round to stand.

Wrap-Up

• Clean-Up: Dispose of liquids in a jar or down the sink. Discard all used cups.

• Topics of Discussion: – Vaccines and Cures– Famous epidemics

• Black Plague in Europe• Smallpox in North America• Tuberculosis• Influenza Pandemic of 1918-1919

Credit: Vanderbilt Students Volunteer for Science