Infectious Disease Lab

How does an Infectious disease spread?

Copyright 2005 by Jennifer Doherty and Dr. Ingrid Waldron, Department of Biology, University of Pennsylvania


An infectious disease is any disease caused by germs that can be spread from one person to another.  Germs include viruses, bacteria and protozoa.  Scientists call these germs pathogens.  What are some infectious diseases?


What are some diseases that are not infectious?


The activity we will be doing today will simulate the spread of an infectious disease.  A simulation is a simplified demonstration of how an infectious disease can spread through a population.  Our simulation will show how one person who is infected with a disease can infect other people, who in turn infect others.




  1. Your teacher will give everyone a cup filled with a clear solution.  This solution represents your body.  One person in the class will have a cup that has been “infected.”

    Obviously, you should not drink from the cup.  (In laboratory activities you should never drink or eat anything unless your teacher tells you that it is safe to do so.)

  2. In this part of the laboratory, you will interact with two other students.

    To interact with another student, pour all of your solution into your partner’s cup.  Then have your partner pour all of the mixed solution back into your empty cup.  Finally, pour half of the mixed solution back into your partner’s empty cup.

    Wait for the signal from your teacher, and then move to another part of the classroom and interact with a second student.  Wait for the signal from your teacher, and then move to another part of the classroom and interact with a third student.  After you have finished your third interaction, return to your seat.

    Estimate how many people you think will be infected.____________

  3. Your teacher will come around and put an “infection indicator” in your cup.  If you have exchanged solutions with the original infected person or someone else after they became infected, you are now infected an your solution will turn pink.  If you have not exchanged solutions with anyone who was infected, your solution will not turn color.

    Next, your teacher will ask everyone who is infected to raise their hand.

    How many people were infected?____________

**See the lab for the Data Tables 1 & 2


  1. Use the graph to predict how many people would become infected if you had four interactions. ___________

    How many interactions do you think it would have taken before the whole class became infected? ___________

  2. What are some ways that infectious diseases are transmitted from one person to another?

  3. What are some ways you can prevent the spread of infectious disease?

  4. Our simulation showed the way a disease could spread if the spread of disease depends on person-to-person contact.  Examples of these kinds of disease include pink eye, chickenpox and herpes (lip sores).  Other kinds of diseases, such as colds and tuberculosis, can be spread by germs in the air.  How might the spread of these diseases differ from the spread of diseases that depend on person-to-person contact?

  5. The spread of the disease in our simulation was very rapid.  Within a few minutes many people were infected.  In real life, infections do not spread as rapidly as in this simulation.  Why is the spread of infections slower in real life?

  6. In addition to exposure to germs or pathogens, what other factors influence your risk of getting an infectious disease?  What defenses does your body have that can prevent you from getting sick, even when you have been exposed to a pathogen?

  7. Once you have caught a cold or flu, you do not stay sick forever.  How does your body eventually get rid of the viruses that cause a cold or flu?

  8. A person who becomes infected with HIV virus is unable to get rid of the HIV virus.  With highly effective modern medical treatment, a person may survive a long time with an HIV infection, but an untreated HIV-infected individual is very likely to develop AIDS and die.  Why is a person with an HIV infection unable to get rid of this infection the way a person can get rid of an infection with a cold or flu virus?