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Topic B6 of OCR Gateway Science A is called Global challenges because it takes the biology you have already met and points it at three of the biggest problems facing humanity: keeping people healthy, feeding a growing population, and protecting the environment we all depend on. This first lesson opens the health strand by asking a deceptively simple question — what does it actually mean to be healthy? — and then sorting the diseases that threaten health into two great families: communicable (infectious) diseases that can be passed on, and non-communicable diseases that cannot. Getting these definitions and categories secure now makes every later lesson on pathogens, the immune system, vaccines and lifestyle disease far easier to follow.
By the end of this lesson you should be able to define health as more than the absence of disease, distinguish communicable from non-communicable diseases with examples, explain how different conditions can interact so that one disease makes another more likely, and outline the main factors that affect a person's health.
It is tempting to think of health as simply "not being ill", but the widely used definition is broader and more useful:
Health is a state of physical, mental and social wellbeing, not merely the absence of disease.
Breaking that down:
A person can be free of any diagnosed disease and yet be unhealthy — for example, someone who is severely isolated, anxious, or living in poor housing. Equally, a person with a long-term managed condition such as well-controlled diabetes may enjoy good overall wellbeing. Recognising all three dimensions is the first big idea of B6.
Exam Tip: If a question asks you to "define health", the marks are for the whole definition — physical, mental and social wellbeing, and the phrase "not merely the absence of disease". Writing only "not being ill" is a common way to drop the marks.
A disease is a condition that stops part of the body working properly. Diseases divide into two main categories.
| Category | What it means | Can it be passed between people? | Examples |
|---|---|---|---|
| Communicable (infectious) | Caused by a pathogen (a disease-causing microorganism) | Yes — it can spread from person to person (or from another organism) | Measles, influenza, HIV/AIDS, tuberculosis, malaria, food poisoning |
| Non-communicable | Not caused by a pathogen; usually develops over a long time | No — it cannot be caught or passed on | Coronary heart disease, most cancers, type 2 diabetes, asthma, cirrhosis of the liver |
The word communicable comes from the same root as "communicate" — these diseases can be communicated (passed on) from one host to another. The agent that causes them is a pathogen: a bacterium, virus, fungus or protist. You will study pathogens in detail in the next lesson.
Non-communicable diseases (NCDs), by contrast, are not caused by a pathogen and cannot be spread. They tend to develop slowly and are strongly linked to risk factors such as diet, exercise, smoking and inherited genes. They are the focus of Lesson 6.
Exam Tip: A very common trap is to assume "infectious = bacteria/viruses only". Pathogens also include fungi (such as athlete's foot) and protists (such as the malaria parasite). And remember: a disease being communicable tells you it is caused by a pathogen, but says nothing about how serious it is.
Diseases do not occur in isolation — having one condition can make a person more vulnerable to others. This idea of interactions between diseases is explicitly required by the specification, so learn a few clear examples.
Worked examples of interacting diseases:
The lesson from all of these is that the body is a connected system: a problem in one part rarely stays contained, which is one reason preventing disease in the first place matters so much.
Whether a person stays healthy depends on far more than chance. The main factors include:
These factors interact too. Poverty, for instance, can mean a poorer diet, more stress, worse housing and greater exposure to pathogens all at once — which is why health is so strongly linked to a person's wider circumstances.
Exam Tip: When a question asks for "factors that affect health", give a range (diet, stress, life situation, exposure to pathogens) rather than several versions of the same idea. Examiners reward breadth.
Disease does not only affect the individual who is ill. It also has a wider cost to society and the economy:
This is one reason why prevention — stopping disease before it starts — is such an important idea in B6: keeping people healthy reduces suffering and the burden on health services and the wider economy.
Exam Tip: A question may ask why governments invest in prevention (such as vaccination or healthy-eating campaigns). A strong answer is that prevention reduces both the human cost (illness and suffering) and the financial cost of treating widespread disease.
The mix of diseases that affects people is not the same everywhere, and OCR expects you to appreciate this in broad, qualitative terms (you do not need to memorise figures).
These patterns can change over time: as a country develops clean water, sanitation and vaccination, the burden tends to shift from communicable towards non-communicable disease. This is why improving basic conditions — clean water, sanitation, vaccination and nutrition — has such a large effect on health worldwide.
| Misconception | The correct idea |
|---|---|
| "Health just means not being ill" | Health is physical, mental and social wellbeing, not merely the absence of disease |
| "All diseases can be caught" | Only communicable diseases spread; non-communicable diseases cannot be passed on |
| "Mental illness is not a real health problem" | Mental wellbeing is part of health; conditions such as depression are genuine illnesses |
| "Infectious diseases are only caused by bacteria and viruses" | Pathogens also include fungi and protists |
| "One disease has no effect on any other" | Diseases interact — e.g. a weak immune system leads to more infections; HPV can lead to cervical cancer |
Question (6 marks): Explain what is meant by health, and describe the difference between communicable and non-communicable diseases. Use examples.
Mid-band response: "Health means being well and not having a disease. Communicable diseases can be passed from person to person, like flu. Non-communicable diseases cannot be passed on, like heart disease."
Examiner-style commentary: This earns marks for the basic distinction between the two disease types with one example each. It is held back by an incomplete definition of health ("not having a disease" misses the wellbeing dimensions) and by giving no cause for each disease category. To climb a band, give the full health definition and state that communicable diseases are caused by pathogens.
Stronger response: "Health is a state of physical, mental and social wellbeing, not just the absence of disease. Communicable (infectious) diseases are caused by pathogens and can spread between people — for example measles, which is caused by a virus. Non-communicable diseases are not caused by pathogens and cannot be passed on; they often develop slowly and are linked to lifestyle, for example coronary heart disease."
Examiner-style commentary: A clear, accurate answer with the full definition of health, the cause of each disease category, and a correctly classified example of each. To reach the top band, add that diseases can interact and give an example of that interaction.
Top-band response: "Health is a state of physical, mental and social wellbeing, and is not merely the absence of disease — a person can be free of any diagnosed illness yet be unhealthy because of poor mental or social wellbeing. Communicable diseases are caused by pathogens (microorganisms such as bacteria, viruses, fungi or protists) and can be passed on from one host to another; an example is measles, caused by a virus. Non-communicable diseases are not caused by pathogens, cannot be spread, and tend to develop over a long time in response to risk factors such as diet and smoking; an example is coronary heart disease. Importantly, the two categories can interact: infection with certain HPV viruses (communicable) can lead to cervical cancer (non-communicable), and a disease that weakens the immune system makes a person more vulnerable to further infections."
Examiner-style commentary: Full marks. The answer gives the complete definition of health with the wellbeing dimensions, defines and exemplifies both disease categories with their causes, and — crucially — shows that diseases interact, with a precise example linking the two categories. This is exactly the breadth and accuracy the top band requires.
This content is aligned with OCR Gateway Science A GCSE Biology (J247), Topic B6 Global challenges. Refer to the official OCR specification document for the exact wording.