KS3 · Biology

Differences between infectious and non-infectious disease

Your friend's cold can become your cold. Your friend's type 2 diabetes never can. What splits the two?

Biology · Health and disease

Infectious or not? You decide

Pick a disease, then pick a side. Ask yourself: is a pathogen the cause, and can it be passed from one organism to another?

Still to sort

Infectious (0)

Caused by a pathogen and can be passed from one organism to another.

Where the line is: Both parts must be true: a pathogen causes it AND it can be passed on.

Non-infectious (0)

Cannot be passed from one organism to another.

Where the line is: You cannot catch it by being close to someone who has it.

13 of 13 still to sort.

A disease is a persistent deviation from a person's normal appearance, body function or behaviour. Diseases can be infectious or non-infectious. Place each one and commit before you read the reason.

Biology · Pathogens

Germs, bacteria, pathogens: what do you really think?

You have just sorted measles, TB, athlete's foot and malaria. Now someone in your class says: "Bacteria? Get rid of the lot, they're what make you ill."

Which is closest to what you think right now?
How sure are you?

How measles passes from one person to the next

Step through it. The last two stages are about stopping the spread.

Non-infectious · Coronary heart disease

?

Reason it through

Why can a blocked coronary artery damage the heart?

Link 1 of 4

First link · your turn

What do the coronary arteries do for the heart?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Infectious vs non-infectious disease

InfectiousvsNon-infectious

You have sorted the diseases. Now here is the rule in one place.

Focus

What causes it

Infectious

A pathogen

Non-infectious

A variety of risk factors, including genetics (for example a faulty gene) and lifestyle factors

The insight

The cause is the dividing line: a pathogen on one side, risk factors on the other.

Can it be passed on?

Infectious

Yes, from one organism to another

Non-infectious

No. You cannot catch it by being in close contact with someone who has it

What reduces it

Infectious

Hygiene (such as washing hands) and vaccination, as measles showed

Non-infectious

Exercising regularly and eating a balanced diet with fruit and vegetables help reduce the risk. Smoking, high blood pressure, obesity, and drinking alcohol or misusing other drugs are risk factors

Who or what it affects

Infectious

Plants as well as animals

Non-infectious

People of all ages in all regions, disproportionately those living in poverty (for example through less access to healthy food). It often takes a long time to develop and lasts a long time

Predict, then check · Type 2 diabetes

Type 2 diabetes is a disease in which a person cannot control their blood sugar (glucose) level. Its symptoms include frequent urination, excessive thirst and cuts that are slow to heal.

If type 2 diabetes is left untreated, what can it cause problems with?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

One question sorts any disease: can it be passed on from one organism to another?

What you need to know

  • A disease is a persistent deviation from a person's normal appearance, body function or behaviour.
  • Diseases can be infectious or non-infectious.
  • Infectious diseases are caused by pathogens and can be passed from one organism to another.
  • Have a goSam sits next to a classmate with a disease all lesson, then says: "I'm definitely going to catch it." What would have to be true about the disease for Sam to be right?

    It would have to be infectious: caused by a pathogen that can be passed from one organism to another.

    Sitting close only matters for a disease that can be passed on, and not every disease can be.

  • A pathogen is a virus, bacterium or other microorganism, such as a fungus or a protist, that causes disease.
  • Not all microorganisms cause disease: not all bacteria are pathogens, and some gut bacteria help keep us healthy.
  • Have a goWhich one is NOT a pathogen: a virus that causes a disease, a bacterium that causes a disease, or a gut bacterium that helps keep us healthy?

    The gut bacterium that helps keep us healthy.

    A pathogen is picked out by causing disease, so being a bacterium is not enough; not all bacteria are pathogens.

  • Measles is caused by a virus, TB by a bacterium, athlete's foot by a fungus and malaria by a protist.
  • Non-infectious diseases cannot be passed on, so you cannot catch diabetes or cancer by being close to someone who has it.
  • Non-infectious diseases are caused by a variety of risk factors, including genetics and lifestyle factors.
  • Have a goJay says: "I've never been near anyone with a non-infectious disease, so I can't be at risk of one." Where does Jay's reasoning go wrong?

    Non-infectious diseases are not caught from other people; risk factors such as genetics and lifestyle cause them.

    Jay is treating a non-infectious disease like an infectious one, but closeness to other people is not what puts someone at risk.

  • Smoking, high blood pressure, obesity, and drinking alcohol or misusing drugs are risk factors; exercise and a balanced diet help reduce the risk.

The big picture

Every disease you meet can be sorted with one question: is it caused by a pathogen that can be passed from one organism to another? If yes, it is infectious. If it cannot be passed on, it is non-infectious, and risk factors such as genetics and lifestyle are the causes.

Key points

1A disease is infectious if a pathogen causes it and it can be passed from one organism to another.
2A pathogen is a virus, bacterium or other microorganism, such as a fungus or a protist, that causes disease; not all bacteria are pathogens.
3Non-infectious diseases cannot be passed on and are caused by a variety of risk factors, including genetics and lifestyle.
4Measles spreads in droplets of mucus that other people breathe in, and the MMR vaccination is the best way to prevent the spread.

Worked example

Problem

Two made-up diseases. Disease A is caused by a protist and can be passed from one person to another. Disease B cannot be passed from one person to another, and smoking and obesity are among its risk factors. Decide whether each is infectious or non-infectious, and give a reason.

⚠ Watch out

Thinking that all bacteria, or all microorganisms, cause disease. A pathogen is a microorganism that causes disease, and some bacteria in the gut help keep us healthy.

🧠

Memory hook

Two things must both be true for infectious: a pathogen is to blame AND it can be passed on. If you cannot catch it from someone, it is non-infectious.

✓

Check yourself

Which one of these is the odd one out, and why: measles, tuberculosis, scurvy, malaria?

Flashcards

(14)
What is a disease?
A persistent deviation from a person's normal appearance, body function or behaviour.
What makes a disease infectious?
It is caused by a pathogen and can be passed (spread) from one organism to another.
How is a non-infectious disease different, and what causes it?
It cannot be passed on from one organism to another. A variety of risk factors, including genetics and lifestyle, cause it.
What is a pathogen?
A virus, bacterium or other microorganism, such as a fungus or a protist, that causes disease.
Are all bacteria pathogens?
No. Not all bacteria cause disease, and some bacteria living in the gut help keep us healthy.
Match the pathogen type: measles, TB, athlete's foot, malaria.
Measles: virus. TB: bacterium. Athlete's foot: fungus. Malaria: protist.
How does measles spread?
An infected person coughs or sneezes, and droplets of mucus containing the virus are breathed in by other people.
What is the best way to prevent the spread of measles?
The MMR vaccination (measles, mumps and rubella).
What do you know about TB's cause and treatment?
Bacteria cause it, it often affects the lungs, and it can be treated with antibiotics.
Name some risk factors for non-infectious diseases.
Smoking, high blood pressure, obesity, and drinking alcohol or misusing other drugs. Genetics also plays a part.
What happens in coronary heart disease?
Coronary arteries can become blocked, so not enough oxygen and glucose reach the heart muscle cells and they can be damaged.
What is cancer?
A cell in the body divides uncontrollably and forms a tumour.
What are the symptoms of type 2 diabetes?
Frequent urination, excessive thirst and cuts that are slow to heal.
What causes scurvy, and is it infectious?
A lack of vitamin C causes it. It is non-infectious.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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How this lesson was checked. This KS3 Biologylesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 9 October 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.