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### Epidemic! The Handshake Game

#### by NIMBioS

Click to enlarge images

Photo By Bart Everson, via Wikimedia Commons

Whether it’s SARS or Bird Flu, the common cold or meningitis, outbreaks of disease are the subject of big headlines and also big science to fight them. Many scientists and mathematicians are working together to study how diseases spread and to create models that predict the progress of epidemics and how to best control them. In this game, participants will learn a simple disease model by being an active participant in a mock “outbreak” of handshake disease. This game was created by Rebecca L Smith, DVM MS PhD, post-doctoral associate at the Cornell University College of Veterinary Medicine.

Subject Matter: Life Science. Mathematics, Medicine

Activity Materials
Scraps of paper with each participant’s name, placed in a hat or box to draw from randomly
Notecards & pencils for recording participants’ handshakes (one per participant)
Masking tape or chalk for marking out boxes on floor
For Advanced Game Only: Some sort of “valuable”: we use chocolate kisses. See game play for details.

Vocabulary
There are three main model classes used in this activity:

1. Susceptible Class [S] – People in this class don’t have the disease, but are all capable of contracting it. In the beginning of the game, everyone is “susceptible”.

2. Infected Class [I] – People in this class currently have the disease.

3. Recovered Class [R] – People in this class have had the disease, but are now over it and no longer can pass it to others. People in this class cannot get the disease again. (They now have immunity.)

Model – A representation of how something works, often much simplified.

SIR Model – A disease model that has susceptible, infected and recovered classes. This is considered by scientists and mathematicians studying disease epidemics to be one of the simplest examples of a disease model.

What to Do
Basic Game Setup:

Using masking tape or chalk, make 3 boxes on the floor and label them S, I, R. The layout should be similar to:

Be sure to make the boxes large enough for all participants to stand in comfortably. Then make lines to connect them as shown.

Playing the basic game:

1. Put each participant’s name into a hat, then give each participant an index card numbered 1-5 on one side.
2. Ask them to introduce themselves to another participant, shake hands, and write the other participant’s name down on their cards next to #1. Repeat this 3-5 times (fewer if the group is small, more if large).
3. Ask all the participants to go stand in the S box. They are susceptible: no one is sick, but anyone can become sick.
4. Draw one participant’s name from the hat and declare that he/she was infected with “handshake disease” before playing; instruct that participant to move into the I box to represent infection. Explain that he/she will infect the next 3 people he/she shakes hands with.
5. Ask the participant in the I box to read the first name from their index card and have that participant move to the I box. Then have each of those 2 participants read the next name on their list (for the new I, it should be the next name after the original I’s name), and have those participants move over. Repeat with the (probably 4) participants now in the I box. Then declare that the original I is cured and have him/her move into the R (recovered) box.
6. Repeat until either there is no one in S or all participants in I have read the 3 names after their “infecting” handshake.

Notes on basic play:

You will likely have participants in the I box reading the names of other participants in the I box. Explain that once you have handshaking disease, you cannot get it again. If a participant in the I box reads the name of a participant in the R box, explain that once you have recovered, you will not get sick again.

Some participants may remain in the S box. This is a good example of the stochasticity (randomness) of disease outbreaks – some people are not exposed, just by chance.

You can add in graphing or networking: record the number of participants in the I box at each “timepoint” (handshake number) in a histogram, or draw the path of connection by writing the first participant’s name on the left side of the board, then drawing an arrow to connect it to the names of the 3 participants he/she infected, and repeat for each of the infected participants.

There are two additional classes in the advanced game:

1. Vaccinated Class [V] – People in this class have received an available vaccine for the disease, which will help to prevent them from getting infected. In this particular game, the vaccine protects the person from getting it the first time, but not the second time.

2. Quarantined Class [Q] – People in this class will limit their contact with other people during the outbreak. In this particular game, it means they will only have to shake hands with one person, instead of 5.

Using masking tape or chalk, make 5 boxes on the floor and label them S, I, R, V and Q. The layout should be similar to:

Be sure to make the boxes large enough for all participants to stand in comfortably. Then make lines to connect them as shown.

Playing the advanced game:

1. You will need some sort of “valuable” (we use chocolate kisses). Give 3 to each participant with a new index card.
2. Explain that everyone can now buy themselves either a vaccine (for 1 piece) or quarantine (for 2 pieces). If they are vaccinated, they will protected from infection the first time, but will get infected the second time. If they are quarantined, they only have to shake hands with 1 person. If they get infected, they have to give back all their valuables. Have the participants make their control choice (vaccine, quarantine, or nothing) and pay for it with their valuables.
3. Repeat the handshaking as in the basic game, the only difference now is that quarantined people only shake hands with one person.
4. Have the participants set up in the boxes as before, but vaccinated participants stand in the V box and quarantined participants stand in the Q box. Draw a new participant at random to be the initial infected (don’t take their valuables, though – be fair). Repeat the moving process, with the necessary additions: participants from the S or Q box go to the I box on their first exposure, but participants from the V box move into the S box with their second exposure. Don’t forget to take the valuables of the participants who are infected.
5. Repeat until a time when no one is moving into the I box.

Have the participants make conclusions about which control method was best. It is often useful to play this game multiple times; encourage the participants to discuss together which method to use.

Notes on advanced play:

The participants may discover for themselves the advantage of “herd immunity”: if everyone is vaccinated, no one will be infected. They may also learn about “freeloading”: if most people pay for control, a person who doesn’t pay for control is less likely to be infected because he/she is taking advantage of the herd immunity provided by the others.

Discuss the effect of quarantine on shutting down the infection cycle, then the practicality of quarantine in most situations (the need for food, going to work, socializing).

If you have groups of friends among your participants, you can discuss stratification: did the disease move faster through one group than through the class at large? Did the disease stay within a group because they only shook hands with each other?

Topics for Science Class Discussion

Draw the model, as it is represented on the floor, onto a board. How would you change representation if:

• Instead of recovering and not being able to be infected again, those that are infected become susceptible again? (Example: common cold)
• Instead of recovering, some people, the very young or the elderly perhaps, are not able to recover and die (Example: malaria)

Extended Activities and Links

Video of Dr. Folashade Agusto, a past postdoctoral fellow at the National Institute for Mathematical and Biological Synthesis (NIMBioS) and now faculty at Austin Peay University. Fola conducts research involving mathematical analysis and optimal control of transmission dynamics of infectious diseases, focusing specifically on bovine tuberculosis, malaria and avian influenza. (1 min 53 sec)
http://www.nimbios.org/videos/agusto_interview

Video of Dr. David Baltimore, Professor of Biology at Caltech, discussing virus outbreaks in the news.
http://media.hhmi.org/ibio/short_clips/baltimore/baltimore_2.mov

Learn facts about different diseases and the controls available at the Center for Disease Control and Prevention
http://www.cdc.gov/DiseasesConditions/

___________________

In Biology by Numbers, learn about the ways math can solve biological problems. Produced by the National Institute for Mathematical and Biological Synthesis (NIMBioS). NIMBioS brings together researchers from around the world to collaborate across disciplinary boundaries to investigate solutions to basic and applied problems in the life sciences. NIMBioS is sponsored by the National Science Foundation, the U.S. Department of Homeland Security, and the U.S. Department of Agriculture with additional support from The University of Tennessee, Knoxville.

The views expressed are those of the author and are not necessarily those of Science Friday.