How Germs Spread
Learning Objectives
Students will be able to:
- Identify three ways germs spread: contact, droplets, and airborne
- Give examples of each type of transmission
- Explain why some diseases spread more easily than others
- Describe how sneeze droplets travel through the air
The Big Question
"How do germs get from one person to another?"
Three Ways Germs Travel
Germs have different ways of getting from a sick person to a healthy person:
1. Contact (Touching)
Direct Contact: Touching someone who is sick (handshake, hug)
Indirect Contact: Touching something a sick person touched (doorknob, toy, phone)
Examples: Stomach bugs, pink eye, some skin infections
2. Droplets (Spray)
When someone coughs, sneezes, or talks, they spray tiny droplets from their mouth and nose.
These droplets are big and heavy, so they fall to the ground within about 6 feet (2 meters).
Examples: Flu, colds, strep throat
3. Airborne (Floating in Air)
Some germs can float in the air for a long time in very tiny particles called aerosols.
These particles are so light they can stay in the air for hours and travel far!
Examples: Measles, chickenpox, COVID-19, tuberculosis
Activity: The Sneeze Test (10 minutes)
See How Far Germs Can Travel!
Materials: Spray bottle with water, measuring tape, paper targets
- Set up paper targets at 3 feet, 6 feet, and 10 feet away
- Have the teacher spray the water bottle (like a sneeze) toward the targets
- Check which targets got wet
- Discuss: How far did the "sneeze" travel?
Real sneeze facts: A sneeze can travel at 100 miles per hour and spray droplets up to 27 feet! But most large droplets fall within 6 feet.
Droplets vs. Aerosols: What's the Difference?
| Droplets | Aerosols |
|---|---|
| Bigger and heavier | Super tiny and light |
| Fall to ground quickly | Float in the air for hours |
| Travel about 6 feet | Can fill a whole room |
| From coughs and sneezes | From breathing, talking, singing |
| Staying 6 feet away helps | Need good air flow to help |
Important!
Airborne diseases are harder to avoid because the germs can float around a room even when the sick person is far away or has already left!
High Risk Places
- Crowded classrooms
- Buses with closed windows
- Waiting rooms
- Indoor parties
- Anywhere crowded with poor air flow
Lower Risk Places
- Outside in the park
- Rooms with open windows
- Spaces with fewer people
- Places with good air filters
- Anywhere with fresh air
The Chain of Infection
For germs to spread, they need a "chain" of events:
Break any link in the chain, and you stop the spread!
Activity: Sort the Diseases (10 minutes)
Sort these diseases by how they mainly spread:
Diseases: Cold, Stomach bug, Chickenpox, Pink eye, Flu, Measles, Food poisoning
| Contact/Surface | Droplets | Airborne |
|---|---|---|
| Stomach bug | Cold | Chickenpox |
| Pink eye | Flu | Measles |
| Food poisoning |
Note: Many diseases spread in more than one way!
Science Notebook (10 minutes)
Draw and answer:
- Draw a picture showing the three ways germs spread (contact, droplets, airborne)
- Why are crowded places with poor air flow risky for spreading germs?
- What's the difference between droplets and aerosols?
Key Takeaways
- Germs spread by contact (touching), droplets (spray), and airborne (floating)
- Droplets are bigger and fall quickly; aerosols are tiny and float
- Airborne diseases are hardest to avoid because germs float in the air
- Crowded, poorly-ventilated spaces help germs spread faster
- Breaking the chain of infection stops germs from spreading
Vocabulary Words
Transmission
The way germs spread from one person to another.
Droplets
Small drops of liquid that spray when you cough or sneeze.
Airborne
Floating in the air. Airborne germs can stay in the air for a long time.
Aerosol
Super tiny particles or droplets that can float in the air.