5.1 Health and Disease

A free GCSE Biology lesson for AQA (8461) from OBA School: what health means, communicable and non-communicable disease, how health problems interact, and using health data. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe health as physical and mental wellbeing, not just the absence of disease
• Explain the difference between communicable and non-communicable diseases
• Describe how different types of disease can interact in the body
• Use percentages and rates to compare health data from groups of different sizes
• Explain why a correlation in health data does not prove that one factor causes another

Key words

• Health: A state of physical and mental wellbeing.
• Disease: A condition that stops part of the body (or a plant) working properly. Disease is a major cause of ill health.
• Communi- cable disease: An infectious disease caused by a pathogen. It can be passed from one person, animal or plant to another.
• Non- communi- cable disease: A disease that cannot be passed from one person to another, for example coronary heart disease or type 2 diabetes.
• Pathogen: A microorganism that causes infectious disease: a virus, bacterium, protist or fungus.
• Correlation: A link between two variables in a set of data. It does not on its own show that one variable causes the other.

What is health?

Being healthy is more than "not being ill". Health means physical and mental wellbeing. A person with no disease can still be in poor health if they are very stressed or not eating well.

Disease is a major cause of ill health, but other factors matter too:

• Diet; How it can affect health Too little food, too much food or an unbalanced diet can lead to deficiency diseases, obesity or a weakened immune system.
• Stress; How it can affect health Long-term stress is linked to poor mental health, high blood pressure and getting ill more often.
• Life situation; How it can affect health Where you live, your income, housing, clean water, sanitation and access to healthcare or vaccines all affect health.

Key fact: Health = physical and mental wellbeing. Diet, stress and life situation all affect it, as well as disease.

Communicable and non-communicable diseases

Communicable diseases are caused by pathogens, so they can spread. Non-communicable diseases are not caused by pathogens and cannot be caught from someone else. They usually last a long time and develop slowly.

• Measles, HIV and influenza (viruses); Non-communicable Coronary heart disease
• Salmonella food poisoning, gonorrhoea (bacteria); Non-communicable Type 2 diabetes
• Malaria (protist); Non-communicable Most cancers
• Athlete's foot, rose black spot (fungi); Non-communicable Lung and liver diseases caused by smoking or alcohol

Exam tip: Ask: "Is a pathogen the cause?" If yes, the disease is communicable.

How health problems interact

Different types of disease often act together. One health problem can make another more likely.

• Immune system defects (for example in advanced HIV infection) mean a person is more likely to suffer from infectious diseases.
• Viruses living inside cells can trigger changes that lead to cancer. Human papillomavirus (HPV) can cause cervical cancer.
• Immune reactions first caused by a pathogen can trigger allergies such as skin rashes and asthma.
• Severe physical ill health, such as a long illness or injury, can lead to depression and other mental illness.

Key fact: Cervical cancer itself cannot be caught, but the HPV virus that can trigger it is spread by sexual contact. This is why girls and boys in the UK are offered the HPV vaccine.

Using health data

Health data are often shown in tables, bar charts, histograms or scatter graphs. To compare groups of different sizes, do not compare the raw numbers. Work out a percentage or a rate per 100 000 people.

Worked example: comparing two towns

In one winter, Town A (population 48 000) had 1320 cases of a flu-like illness. Town B (population 125 000) had 2900 cases.
Town A: 1320 ÷ 48 000 × 100 = 2.75%. Rate = 1320 ÷ 48 000 × 100 000 = 2750 per 100 000.
Town B: 2900 ÷ 125 000 × 100 = 2.32%. Rate = 2320 per 100 000.
Town B had more cases, but Town A had the higher proportion of people ill.

Answer: Town A has the higher rate (2750 per 100 000)

A scatter graph can show a correlation between two factors, such as hours of exercise and blood pressure. A correlation does not prove cause. Another factor may cause both, or the link may be chance in a small sample. Scientists look for a mechanism (a biological explanation) and repeat studies on large samples.

Common mistakes

• Saying health is "not being ill". It is physical and mental wellbeing.
• Comparing the number of cases in groups of different sizes. Use percentages or rates per 100 000.
• Saying a correlation proves that one factor causes the other.
• Thinking cancer is communicable because HPV can trigger it. The virus is passed on, the cancer is not.
• Calling any long-lasting disease "non-communicable". HIV lasts for life but is caused by a virus, so it is communicable.

Revision questions

Try these, then check your answers below each one.

Question 1. Which is the best definition of health? (Choose from: Not having any disease, A state of physical and mental wellbeing, Being physically fit, Having a strong immune system.)

Answer: A state of physical and mental wellbeing

Working: Health is a state of physical and mental wellbeing. Someone with no disease can still be in poor health, for example through stress.

Question 2. True or false? Cervical cancer can be caught directly from another person.

Answer: False

Working: False. The cancer itself cannot be caught. The human papillomavirus (HPV), which can trigger cervical cancer, is passed on by sexual contact.

Question 3. A person has a defect in their immune system. What is most likely? (Choose from: They will develop an allergy to pollen, They will catch infectious diseases more often, They will develop type 2 diabetes, They cannot become depressed.)

Answer: They will catch infectious diseases more often

Working: The immune system fights pathogens. If it does not work properly, the person is more likely to suffer from infectious (communicable) diseases.

Related lessons

• Previous lesson: 4.9 Factors Affecting Transpiration
• Next lesson: 5.2 Pathogens and Disease
• In this chapter: 5.3 Growing Bacteria in the Lab
• In this chapter: 5.4 Preventing Bacterial Growth
• In this chapter: 5.5 Preventing Infections

Continue in the full course

This lesson is section 5.1 (AGCBH0501) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.