Students investigate how diseases are spread and discover how to prevent transmission between humans and animals. Grades 3-5

aerosol: a suspension of fine solid or liquid particles in gas

contaminate: to make something dirty or impure by accidentally or purposely adding something harmful

disease: a particular abnormal condition that negatively affects the structure or function of all or part of an organism

fomite: objects or materials which are likely to carry infection, such as clothes, utensils, and furniture

germ: a microorganism causing disease

ingestion: consuming something orally

pathogen: a bacterium, virus, or other microorganism that can cause disease

transmission: the act or process by which something is spread or passed from one person or thing to another

vector-borne transmission: infection transmitted to humans and other animals by blood-feeding anthropods, such as mosquitoes, ticks, and fleas

Some people are carriers of disease. Initially, these carriers may appear healthy or show only mild signs of disease. At some point they may eventually get sick, but they may not be recognized as having the disease until they've exposed and infected others. This is one reason why some pathogens can spread so quickly.

Diseases can be spread by direct contact, indirect contact, aerosols or droplets, ingestion or oral transmission, or vectors. Indirect contact transmission is the spread of pathogens through coming into contact with areas where animals live or roam, or objects or surfaces contaminated by an infected animal. Objects or surfaces that may become contaminated with pathogens are called fomites. Some examples of fomites are boots, cages, needles, bedding, clothing, vehicles, and restraint devices. Ingestion or oral transmission occurs when disease-causing agents are ingested from contaminated food or water or by licking or chewing contaminated objects in the environment. Germs can be present even when things (clothing, gloves, shoes, equipment, etc.) appear clean or when animals appear healthy.

Ways to prevent direct contact transmission:

• Isolate sick animals
• Wear gloves when working with sick animals
• Wash your hands after having contact with animals or being in animal areas even if you did not touch the animals

Ways to prevent indirect contact transmission:

• Avoid sharing equipment, or clean and disinfect equipment when sharing is necessary
• Clean and disinfect any equipment used with sick animals or animals with skin lesions
• Dispose of or wash boots and clothing after animal contact
• Wash your hands after having contact with animals or being in animal areas even if you did not touch the animals

Ways to prevent aerosol transmission:

• Increase distance between sick animals and healthy animals and people
• Wear respiratory protection when working with sick animals
• Provide fresh air to animals and people
• Decrease humidity and odor buildup in barns
• Stay away from animal barns if you are sick

Ways to prevent oral transmission:

• Wash your hands
  • After contact with animals or being in animal areas even if you did not touch the animals
  • After cleaning pens or contact with manure
  • Before preparing or handling food
  • After going to the bathroom
• Cook meat to the appropriate temperature
• Store food at the appropriate temperature

Ways to prevent vector-borne transmission:

• Use insect control products
• Work with your veterinarian to check and treat your animals for parasites
• Prevent standing water
• Check for ticks on people and pets

1. Ask the students to raise their hands if they have pets or farm animals. Ask the students to raise their hands if they've ever been to a petting zoo or farm. Discuss the interactions and relationships that students have with animals. 
2. Point out that it is possible for diseases to pass between people and animals. It is important to understand how to protect yourself and others, as well as your animals.
3. Explain to the class that they will explore how diseases are transmitted and discover how to prevent the spread of disease to humans and animals.

Activity 1: Disease Transmission and Outbreak

Teacher Preparation: Half fill 10% of the cups with baking soda water. (For example, if there are 20 students, fill 2 cups with baking soda water). Half fill the remaining cups with distilled water. Place numbered nametags with the corresponding cup. Make note of which cups contain baking soda water. Set a Behavior Card under each cup. Pair the baking soda cups with a "Participants in multiple open, county, and state shows" card.

Alternative Materials: Yellow food coloring (uninfected) and blue food coloring (infected) may be used instead of baking soda and phenol red. Any shade of green will represent infection at the end of the swapping activity, and may better demonstrate varying severity of illness. These materials may be easier to obtain.

1. Using a projector, go through the first three elementary Bring Home the Blue, Not the Flu! modules—All About Germs, Signs of Sickness, and How Germs Spread—as a class, or have students work through the modules on individual computers.
2. Provide each student with one cup, the associated Behavior Card, the corresponding numbered nametag, and an Outbreak Investigation activity packet. 
3. Instruct students to put on their numbered nametag and review their behavior card. Tell them that they will be swapping fluids with other participants and each fluid swap should occur with a different person.
4. Ask students to move about the room and exchange fluids according to the instructions on their behavior card.
   • To exchange fluids, one person will dump all of the contents of their cup into the other person's cup.
   • Return half of the solution back to the empty cup. (Demonstrate with two water cups.)
   • Record the number of the person they exchanged with on their Fluid Swap Record in their packet.
5. Students should repeat step 4 as many times as specified on their behavior card. Remind students that each swap should be with someone they haven't already swapped with, and that they should only swap as many times as their behavior card indicates.
6. When swapping has finished, instruct students to return to their desks with their cups.
7. Add 2-3 drops of phenol red to each cup. A pink color change (bright or faint) indicates a positive result—this person is now considered "infected." No color change is "uninfected."
8. Work with the class to fill out Table 1 in their packets. Ask all with one exposure to raise their hands or stand. Discuss mild to severe infection and individuals who are at risk of severe complications (pregnant, very young or old, immunocompromised). Have the students answer questions 2 and 3 individually before discussing as a class.
9. Ask the students, "How did the number of people infected increase with each round of interactions?" Assuming one person was initially infected, fill out Table 4 and Graph 5.
10. Have the students answer questions 6 and 7 individually and then discuss:
    • What do you notice about the rate of increase in the number of infections? (Discuss the doubling of number of infections in each round.)
    • Does the graph show linear or exponential growth? (exponential growth)
    • If we did this activity long enough, would everyone become infected? Why or why not? (Yes, but the doubling of infection we see in each generation does not continue indefinitely. In the beginning the curve increases exponentially, but then levels out. This pattern is known as logistic growth curve (S-curve). As the number of infected participants increases, it becomes increasingly more likely that an infected participant interacts with another participant that has already been infected. As a result, the number of new infections slows down. This type of growth also assumes that no one has any protection from the infection, such as vaccination.)
11. Ask the class, "How can we determine who was the original source of infection?" Discuss the idea that it's important for participants to realize that if they are infected, but can identify people they swapped with that AREN'T infected, then they could not have been the original source. Working through this should lead back to the people that were originally infected and those that they infected after the first swap.
12. After the discussion, have all "infected" participants stand up and "non-infected" participants remain seated. "Infected" participants should look around at "non-infected" participants. If anyone they exchanged fluids with is sitting, they should sit down as well. Continue this until there are 7-10 participants still standing. Direct the remaining participants to bring their list of people they swapped with to the front of the room and complete the "infection tree" as a class. Students have an "infection tree" in their packet that they can fill out as the group discusses. Completing the tree will require input from participants that remain seated.
13. Once the tree is complete, shade in all bubbles representing people that were "infected" at the end of the activity. Use this diagram to discuss and identify the probable initial source of the infection. Teacher Note: You will only be able to narrow it down to twice as many "suspects" as there were initial infected cups (e.g., starting with two cups means you'll be left with four suspects).
14. Activity Adaptation: Rather than using the "infection tree" to identify the initial source of infection, simply use the "stand up/sit down" method:
    • Have everyone stand up that is infected at the end of the activity.
    • If anyone standing up swapped fluids with anyone that is still sitting (uninfected), they should sit down.
    • Continue this until you're left with twice the number of people standing as you had initially infected cups.
    • One infected cup would result in two people left standing at the end. In this activity, there is no way to determine which person was the original source of infection, but you can share that information with the group.
15. Ask the class, "In a real investigation, how could we distinguish between who was the original source and who they infected? Why can't we do that here?" (In this activity, the potential first exposure to disease for everyone was the same when you were randomly handed a cup that either had water or a baking soda solution. You can't use earlier exposure or timeline to further narrow down who was originally infected and spread the "disease" to the rest of the group.)
16. Ask the students, "How would this investigation be different if you hadn't kept notes about whom you swapped fluids with and in what order?" Have them answer question 9 individually before discussing that one of the difficulties of a true outbreak investigation is that people's memories aren't always that great. It typically takes time for a disease to appear after initial exposure, and it takes even more time for an epidemiological investigation.
17. Ask, "What preventative measures could have been taken to avoid exposure to the disease?" (Lots of possible answers, including vaccination, attending fewer shows, etc.)
18. Ask the class, "How would an airborne disease spread differently? Why?" (In this activity, disease spread was dependent on a very direct, one-on-one interaction. Airborne diseases are able to spread more easily and indirectly from person to person, animal to animal, or animal to person and it often isn't clear when you've been exposed to someone with the disease. In this activity, it was very clear whom you swapped liquids with. It's much more difficult to track who you simply walk by, were in the barn with at the same time, etc.) 
19. Use a bubble blower and see who gets hit with a bubble to model airborne disease spread. Explain that airborne disease spread requires less movement. Some diseases can be transmitted in the air for long distances.

Activity 2: Biosecurity

1. Using a projector, go through the last three elementary Bring Home the Blue, Not the Flu! modules—Fight Germs, Biosecurity: Keep Germs Out, and What Went Wrong at the Fair?—as a class, or have students work through the modules on individual computers.
2. Ask the students if they have ever been to a county or state fair or a livestock show. Explain that 4-H and FFA programs provide opportunities for youth to raise and care for animals and participate in an animal show where they will be judged on the animal's care, health, and growth.
3. Show the FFA & 4-H Students Show Skills at Junior National Livestock Show video.
4. Divide the class into small groups. Provide each group with a stuffed animal, feed samples, and a bucket. Place the show equipment on a table. Explain to the groups that they need to get their animal ready for a show by completing the following tasks:
   • "Inspect" the animal to make sure it is ready for the show.
   • Mix different feed samples in the bucket.
   • Collect the equipment to bring to the show.
5. Shine a black light on each student's hands to demonstrate how diseases can be spread by direct contact and from touching clothing, feed, buckets, equipment, fair food, etc. Demonstrate how pathogens can be spread by shoes by shining the black light throughout the room where students walked.
6. Discuss the importance of handwashing and how and when to wash hands to prevent the spread of disease. Share the Five Steps to Wash Your Hands the Right Way.
   • Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap.
   • Lather your hands by rubbing them together with the soap. Lather the backs of your hands, between your fingers, and under your nails.
   • Scrub your hands for at least 20 seconds. Need a timer? Hum the "Happy Birthday" song from beginning to end twice.
   • Rinse your hands well under clean, running water.
   • Dry your hands using a clean towel or air dry them.
7. Have the students wash their hands and then use the black light again.
8. Invite the students to put on personal protective equipment (PPE) and repeat steps 4 and 5.
9. Discuss how wearing PPE helps to prevent disease transmission.
10. Use the information in the Background Agricultural Connections section to discuss ways to prevent direct contact, indirect contact, aerosol, oral, and vector-borne (infection transmitted to humans and other animals by blood-feeding anthropods, such as mosquitoes, ticks, and fleas) transmission.

After conducting these activities, review and summarize the following key concepts:

• Germs are tiny invaders that can get into our bodies and cause disease. 
• Humans and animals can carry germs that can make each other sick.
• Germs can spread in four main ways—touching, eating, through the air, and carried by bugs.
• Washing your hands is one of the simplest and most effective ways to fight germs.

Activity 1 instructions were adapted from an activity developed by the Indiana State Department of Health.

• Animated Life: Seeing the Invisible
• Bring Home the Blue, Not the Flu Online Modules
• Germ Stories
• Glo Germ Set
• Show Them The Germs!
• The Big Soap-rise (Farm Friends)