OCR GCSE Biology A: Health, disease types and the spread and prevention of communicable disease (J247)

This guide follows the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026). It covers statements B6.3a to B6.3e in Topic B6, Global challenges, section B6.3 “Monitoring and maintaining health”. None of these statements is printed in bold, so they are assessed in both Foundation and Higher Tier papers. Other statements in B6.3, such as named infections and plant defences, are taught on separate pages.

Use it with the revision notes and the practice questions. Course pages: OCR GCSE Biology hub and the printable checklist. To find weak spots first, try the free diagnostics.

What this unit covers

Statement	You must be able to	Tier
B6.3a	Describe the relationship between health and disease	Both
B6.3b	Describe different types of disease, including communicable and non-communicable	Both
B6.3c	Describe interactions between types of disease: HIV and tuberculosis; HPV and cervical cancer	Both
B6.3d	Explain how infections from the four pathogen groups (virus, bacterium, protist, fungus) are passed on in animals and in plants; work with pathogen numbers and numbers of cases, including estimates	Both
B6.3e	Explain how spread may be reduced or prevented in animals and plants (detecting the antigen, DNA testing, visual identification)	Both

The specification also lists maths skills for this section: translating between graphs and numbers (M4a), frequency tables and bar charts (M2c), sampling (M2d) and scatter diagrams for correlation (M2g). They appear in the worked examples below.

Health and disease (B6.3a)

Health is more than not being ill. It is a state of physical, mental and social wellbeing. A person can have no infection and still be in poor health because of stress, isolation or poor sleep. Mental health counts as health, a point the specification itself flags as a common gap.

Disease is a condition that stops part of the body, or a plant, from working normally. The two ideas are linked in both directions:

• Disease lowers health. Pain, tiredness and low energy affect physical health.
• Poor health makes disease more likely. A poor diet weakens the body’s defences, so infections take hold more easily.
• One disease can harm the other dimensions. A long illness can stop someone working or seeing friends (social) and can cause anxiety or low mood (mental).

So disease is one cause of poor health, not the only one. Many diseases are also interlinked, which is the subject of B6.3c.

Types of disease (B6.3b)

The central split is communicable against non-communicable.

	Communicable	Non-communicable
Cause	A pathogen: virus, bacterium, protist or fungus	No pathogen; genes, diet, lifestyle, environment, ageing
Passed between people?	Yes	No
Examples	Influenza, cholera, malaria, athlete’s foot	Cystic fibrosis, scurvy, many cancers, type 2 diabetes

Other useful groupings, all non-communicable:

• Inherited diseases, caused by faulty alleles passed from parents. Cystic fibrosis is one.
• Deficiency diseases, caused by missing nutrients. Scurvy comes from too little vitamin C.
• Diseases linked to lifestyle, such as many cardiovascular diseases.
• Mental illness, which is a disease of mental health with no pathogen.

The specification warns that learners confuse which diseases are inherited and which are caught. Cancer is a good test case. It is not caught like a cold, and it is mostly not inherited either: it usually starts with changes in the DNA of body cells during life. Treat it as non-communicable.

Plants have both types too. A plant virus is communicable. Magnesium deficiency in a plant, which turns leaves yellow, is non-communicable.

Interactions between diseases (B6.3c)

Types of disease affect each other. The specification names two pairs.

HIV and tuberculosis (TB). HIV is a virus that damages the immune system. TB is a bacterial infection of the lungs. A person with HIV is less able to fight bacteria, so they are more likely to develop TB after exposure, and more likely to have a latent TB infection become active. TB then adds further strain to an already weakened body. One communicable disease makes another easier to catch and harder to survive. You do not need the detail of how HIV attacks immune cells for this statement; the cause and effect is the point.

HPV and cervical cancer. Human papillomavirus (HPV) is a virus. A long-lasting infection with certain types of HPV can change the cells of the cervix so that they divide out of control. Here a communicable disease is a cause of a non-communicable one. The cancer itself cannot be passed on.

Other links follow the same logic: malnutrition can weaken defences against infection, and a long infection can lead to depression. When asked to “describe an interaction”, name both diseases, say which direction the effect runs, and give the mechanism in one clause.

How communicable disease spreads (B6.3d)

A pathogen needs a route from an infected host to a new one. The four pathogen groups can each use several routes.

Pathogen group	Animal example	Route
Virus	Influenza	Droplets from coughs and sneezes breathed in
Bacterium	Cholera	Drinking water or food contaminated with faeces
Protist	Malaria	Mosquito vector carries the protist in its saliva
Fungus	Athlete’s foot	Direct contact, and shared damp floors and towels

General routes in animals:

• Direct contact, including body fluids and mother to baby.
• Air, through droplets.
• Water and food, where hygiene or sanitation is poor.
• Vectors, organisms that carry a pathogen without being harmed.

Plants cannot cough, so routes differ. Tobacco mosaic virus spreads by contact, including on hands and tools. Fungal spores of diseases such as ash dieback travel on the wind. Water splash moves bacteria and spores between leaves, contaminated soil spreads root diseases (clubroot of cabbages is caused by a soil protist), and sap-feeding insects can carry viruses between plants. Humans spread plant disease on equipment and in imported plants.

Spread is faster when hosts are crowded, when hygiene is poor, when climate suits the pathogen or vector, and when no one has immunity. Plants grown close together pass leaf-to-leaf infections quickly.

Working with numbers (M2c, M2d, M2g, M4a)

Pathogen numbers. Bacteria divide by binary fission, doubling each time. After n divisions, number = start × 2ⁿ.

Worked example 1. A culture starts with 40 bacteria that divide every 30 minutes. How many are there after 5 hours? How long to pass one million?

• 5 hours = 10 divisions.
• 40 × 2¹⁰ = 40 × 1024 = 40 960, or 4.1 × 10⁴ in standard form to 2 significant figures.
• 40 × 2¹⁴ = 655 360 is below a million; 40 × 2¹⁵ = 1 310 720 is above. So 15 divisions: 15 × 30 min = 7.5 hours.

Real numbers grow slower: food, space or oxygen run out, and the body kills some cells.

Estimating cases from a sample. Counting everyone is often impossible, so a random sample is tested and scaled up.

Worked example 2. A town has 12 000 people. A random sample of 300 is tested and 27 are infected.

• Proportion infected = 27 ÷ 300 = 0.09, or 9%.
• Estimated cases = 0.09 × 12 000 = 1080.

This is an estimate. A larger, random and representative sample gives a better one. Testing only people with symptoms would overestimate it.

Incidence and percentage change. Incidence lets you compare places of different size: new cases per 100 000 people.

Worked example 3. A district of 35 000 people has 84 new cases in a year.

• Incidence = 84 ÷ 35 000 × 100 000 = 240 per 100 000.
• If annual cases fall from 180 to 117, change = (180 − 117) ÷ 180 × 100 = 35% decrease.

Scatter diagrams and correlation. The table gives cases of a vector-borne disease in a clinic against the number of vectors trapped in a month.

Vectors trapped	10	22	35	41	58	66	79
Clinic cases	3	6	10	9	16	19	22

Plotted, the points rise from bottom left to top right close to a straight line: strong positive correlation. As vectors increase, cases increase. Correlation alone does not prove cause; here a known biological link (the vector carries the pathogen) makes cause likely, but another factor such as rainfall could affect both.

Reducing and preventing spread (B6.3e)

Each control method breaks one link in the route from host to host. Match the method to the route.

Route	Control in animals
Contact	Hand washing, isolation of cases, protective clothing
Air	Covering coughs, ventilation, isolation
Water and food	Sewage treatment, clean drinking water, food hygiene
Vector	Mosquito nets, insecticide, draining standing water, removing breeding sites
Host not immune	Vaccination (covered on the immune system page)

For plants:

• Destroy or remove infected plants so they cannot release spores.
• Quarantine and inspect imported plants.
• Clean tools, wash hands and rotate crops so pathogens do not build up in soil.
• Space plants, remove weeds that act as hosts, and control insect vectors.
• Use fungicides on fungal disease, or grow resistant varieties.

Detection lets control start early. The specification lists three methods:

• Visual identification: recognising characteristic symptoms such as a rash, or leaf spots and mosaic patterns. Quick and cheap, but similar symptoms can have different causes and some infected hosts show none.
• Detection of the antigen: a test finds a protein from the pathogen in a sample. It is fast and can be used on site.
• DNA testing: finds pathogen DNA, so it can identify the exact species or strain, even at low numbers.

Detecting a case lets you isolate the host, treat it and trace contacts before the pathogen spreads further.

Worked example 4. Fungicide trial: 100 plants each. Untreated, 64 became infected; sprayed, 21.

• Reduction = (64 − 21) ÷ 64 × 100 = 67%.
• Conclusion: the spray reduced infection by about two thirds, but did not stop it completely. A repeat on more plants would show whether the result is reliable.

Common errors

• Writing that health means “no disease”. Include mental and social wellbeing.
• Calling cancer or heart disease communicable. They are not caught from others.
• Saying HPV “is” cervical cancer. HPV is the virus; the cancer is a separate, non-communicable disease it can cause.
• Treating a vector as the pathogen. The mosquito is the carrier; the protist is the pathogen.
• Giving a control method that does not fit the route, such as mosquito nets for a water-borne disease.
• Stating that a correlation proves one thing causes another.

Next steps

Work through the practice questions, then see the exam preparation page for technique.

Official syllabus

OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), for first assessment in 2018, published by OCR. This page covers statements B6.3a to B6.3e only.