Edward Jenner saved millions of lives, not by finding a cure for a disease but by stopping people from catching it: he created the first vaccine. Now, thanks to Jenner, no one catches smallpox, a horrible, deadly disease. Today, vaccines are used to stop the spread of equally awful diseases, saving lives without us even knowing it.

Answers to quiz

Water-borne diseases - purifying drinking water
Typhoid
Cholera
Dysentery

Food-borne diseases - correct storage and cooking of food
E- coli
Salmonella

Transferred by animals - control of animals
Avian flu
Rabies

Transferred by insects - insecticides and insect repellents
Malaria
Bubonic plague

Air-borne - spread by sneezing or on surfaces - covering face and washing hands
Colds and flu
Chickenpox
Measles

Mimicking the spread of diseases

You will need...

A piece of paper for each student in your class
A clipboard for leaning on (optional)
Each student should have a pen or pencil

How long will it take?

You will need to explain to the class what you will be doing and how the activity will work. You may want to demonstrate with a small group of students (about 4) which can take about 15 minutes. The activity itself my take a further hour if you run it a few times with different people infected or vaccinated. Time will depend on how many people each student can infect, and how quickly you move them between meetings.

What to do...

You can mimic the spread of diseases in a classroom. Read through the following activity. The students may appreciate a short demonstration of the activity with a few students before they start.

1. Start with one person: this is the first infected person. You can do this by handing out a piece of paper to each person with the word 'infected' or 'clear' written at the top of it. Do not tell the class who is infected.

2. Ask your class to walk around the room and chat with each other. It is best if they only speak to one person at a time. When they stop to talk to someone they must shake hands, and show each other their piece of paper.

3. If a person meets someone with the word 'infected' on their paper they too become infected. Each person needs to write down whether they are still 'clear' or if they have been 'infected' on the next line of their paper. It is really important that they don't give away that they are infected: in reality they wouldn't know.

4. They can then carry on chatting to other people, each time showing the person the bottom line of their paper and writing down whether they are still 'clear', still 'infected' or whether they have become 'infected'. You can get them to move randomly, when they want, or ask them all to change at the same time.

5. Once the infected people have shaken hands with - or infected - two or three people, they will start to show symptoms and can sit down. No-one will want to shake hands with them knowing they will be infected.

6. Pretty quickly you will find that the whole class will be sitting down, depending on how many times infected people shake hands with already infected people.  You can stop the activity at any time, after they have each met 2 people, 3 people, or until they are all infected and sitting down.

7.  If there are still some people standing you can then find out if they are infected - has anyone survived the contagion?

8. You may then want to get them to wash their hands, so they don't really spread any colds throughout the entire class!

Variations:

Changing the infectious period...


You can mimic how diseases spread with both long and short infectious periods. Diseases which are contagious for a long while without showing symptoms, like chickenpox, spread more readily.
Allow people to shake hands with ten people before sitting down. They may all spend a long time standing, but quite rapidly the entire class will be infected.

Make people more hygienic...
You can also change the pattern of the spread by changing the behaviour of the people. Give pupils the choice of shaking hands with other people. If they don't want to shake hands (or in reality they wash their hands a lot) they are less likely to catch the disease.

Vaccinate some of the class...
Lastly, when you choose the person to be infected, also choose some people to be vaccinated against the disease. These people cannot be infected or spread the disease. Experiment with different numbers of vaccinated students.

Plotting it out...

You can create a graph of how many people are infected at each stage of this experiment.  The difficult bit is doing it so no one finds out who is infected!

Start with round 1, you know one person is infected.  After round 2, two people will be infected.  At the end of round 3, 4 people will be infected.  After that it becomes less clear who will be carrying the infection, as infected people will talk to infected people... the maximum number of infected people at the end of round 4 will be eight.

Once you get to round 4 you can ask the students to stop (concealing their clipboards except from you), count the number of infected students and make a note.  After each round do the same thing, you should end up with notes that look like this...

Round

Infected

1

1

2

2

3

4

4

7 (maximum 8)

5

12 (maximum16)

6

20 (maximum 32)

7

30 (maximum 64)

When students are asked to sit down after they have been infected for two or three rounds the number of infections will drop.  When students are asked to infect only two other people before sitting down the table will look like this...

Round

Infected (maximum)

1

1

2

2

3

4 (1 sitting, 3 carrying on)

4

7 (2 sitting,  5 carrying on)

5

12 (4 sitting, 8 carrying on)

6

20 (7 sitting, 13 carrying on)

7

33 (12 sitting, 21 carrying on)

You can draw tables for all your variations, including vaccinated people and plot out the graphs.

Curriculum Links

Stopping the spread
Science

Working scientifically

Scientific attitudes

  • understand that scientific methods and theories develop as earlier explanations are modified to take account of new evidence and ideas, together with the importance of publishing results and peer review.


Scottish Curriculum Links:

Science

SCN 3-13b

Biological systems - Body systems and cells

I have contributed to investigations into the different types of microorganisms and can explain how their growth can be controlled.

 

SCN 3-13c

Biological systems - Body systems and cells

I have explored how the body defends itself against disease and can describe how vaccines can provide protection.

Stopping the spread

NorovirusWhat was revolutionary about Edward Jenner's discovery was that it took medicine in an entirely different direction. Doctors no longer just tried to cure diseases once they had happened, they could stop them from spreading from one person to another.

How do diseases spread?

Diseases have a number of different ways of travelling from one person to another, and there are ways of stopping or slowing the spread if you understand how each disease moves. Diseases can be carried in water or food, they can be transmitted by insects or animals, and they can be spread from one person to another by contact with blood or saliva.

On the right is an image of a norovirus, and the picture below shows the molecular structure of a foot and mouth virus.

Foot and mouth virusHowever, no matter how careful people are, it is very difficult to stop the spread of some diseases, particularly those which are air-borne or carried by animals and insects. Smallpox spread from the liquid in the smallpox blisters. Since an infected person had blisters in their mouth, the disease could be spread just by talking to an infected person. A person with smallpox was most likely to pass it on to their family.

Key fact: Diseases spread in many different ways, so to prevent the spread of specific diseases, scientists have to understand how they are transmitted between people.

 

Why do people no longer get smallpox?

A worldwide campaign to get rid of smallpox was started in 1959. As increasing numbers of people were vaccinated against smallpox the cases became fewer and fewer. A person with smallpox who was surrounded by immune people could not pass the disease on, and so the disease could not spread. The last natural case of smallpox was in Somalia in 1977.

A population can be given "herd immunity" like this when around 85% of all people are immune to a disease. Some people cannot receive vaccinations either because they have an immune system disorder or have received an organ transplant. With enough people vaccinated the disease cannot reach those most vulnerable and the disease dies out.

Key fact: If you can vaccinate around 85% of a population against a disease, the disease can't spread, and it will die out.

 

 

Can you match the disease with how it is spread and how this can be prevented? More than one disease fits with each category.

Download the pdf worksheet here.

Water-borne diseases

Food-borne diseases

Transferred by animals

Transferred by insects

Air-borne diseases, spread by sneezing or from droplets on hard surfaces

Prevented by purifying drinking water

Prevented by the correct storage and cooking of food

Controlled by reducing contact with animals, destroying infected animals

Controlled by using insecticides and insect repellents

Controlled by covering the face and washing hands

Diseases

E- coli  
Typhoid Malaria  
Cholera  
Salmonella 
Dysentery 
Colds and flu 
Chickenpox 
Bubonic plague 
Measles 
Avian flu 
Rabies

 

 

Common cold virusMimicking the spread of diseases

Download pdf instructions here.

You will need...

A piece of paper
A clipboard (optional)
A pen or pencil

What to do...

  1. You will be given a piece of paper with the word 'clear' or 'infected' at the top. If you are infected it means you have a horrible, deadly disease!
  2. Move around the class and stop and talk to someone, shake their hand and show them your piece of paper but keep it secret from other people you haven't spoken to yet. (In reality you wouldn't even know yourself if you were infected.)
  3. If you or the person you meet has the word 'infected' write 'infected' on the next line of your paper. If you are both 'clear', write 'clear'.
  4. Move on to another person and repeat steps 2 and 3. Once infected you will infect others! Continue to write 'infected' on the next line of your paper until you have infected a number of people - your teacher will tell you how many! Once you have infected this number of people you will start to show symptoms and can quarantine yourself at the side of the room - after all, no one will want to talk to you now you are clearly ill.
  5. Watch as the number of infected students grows. Has anyone in your class escaped this deadly disease?