Kids need to learn how bacteria and viruses are spread so they can understand how important hygiene and food safety are for their health. Simple classroom activities can show them how quickly and easily germs can infect an entire group when people forget to do simple things, such as washing their hands, leaving food out or sharing food with other people.
You'll need an ultraviolet lamp and a lotion that glows under UV light, such as Glo Germ. You could also use any non-toxic paint that glows when exposed to ultraviolet light. Have the class line up, and cover the first student's hands with the lotion. Have her shake hands with the next student in line, who shakes hands with the next student, and so forth until each student has shaken hands. Turn on the UV lamp to see how many students have been "contaminated," and record your results. Then, have all students wash their hands and repeat the process, except this time you have the first student wash her hands after having the lotion applied. Record your results and compare how hand-washing affected the spread of bacteria.
Have students stand up. Designate one student as the viral "carrier" and give her a sheet of red stickers. Instruct the students to begin circulating around the room once the 60-second timer starts, and instruct the carrier to place stickers on as many students as possible. After 60 seconds, count how many students have been "infected." For round two, give the carrier and three of the infected students each a sheet of green stickers, and repeat the process. After this round, count the number of newly infected students and the total infected, and compare results. Explain that at first only one person spread the virus, but after the virus incubated, others started to spread it as well.
Before class, prepare sandwich bags full of beads. Place 5 in one bag, 10 in another, 20 in another, 40 in another and so on, always doubling the amount. Set a shallow bowl on a table and have students gather around. Hand one bag of beads to each student. Explain that bacteria reproduces quickly, and can double its population in minutes. Your "bead bacteria," however, will double its population every 30 seconds. Have the student with 5 beads empty her bag into the bowl. 30 seconds later, have the student with 10 empty his bag, followed by the student with 20, then 40, and so on until the bowl overflows. Students will see just how quickly a bacterial population can get out of hand.
Sharing a Virus
You'll need three plastic cups: red, yellow and blue. Before class, fill each cup with water and then pour sodium carbonate into the red cup. Tell the class they will pass cups around for a minute or two as though they were sharing drinks, but they shouldn't drink from them; it's just pretend. Tell them, however, to remember which cups they touch. Hand the cups to students and let them pass them around. Afterward, pour some phenolthalein into the red cup, which will cause the water color to change. Ask students who touched the red cup to raise their hands. Explain that they've all been "infected" by just one unknowingly infected person who shared their drink.