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B5.1 Health and Disease

GCSE Combined Science · AQA · Chapter B5: Communicable Diseases

A free GCSE Combined Science: Trilogy lesson for AQA (8464) 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 a state of physical and mental wellbeing
  • 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?

Health means more than "not being ill". It is a state of physical and mental wellbeing. Someone with no disease can still be in poor health if they are under a lot of stress or eat a poor diet.

  • Diet; How it can affect health Too little food, too much food or an unbalanced diet can cause deficiency diseases, obesity or a weaker immune system.
  • Stress; How it can affect health Long-term stress is linked to poor mental health, raised blood pressure and catching infections more often.
  • Life situation; How it can affect health Income, housing, where you live, clean water, sanitation and access to healthcare and vaccines all affect health.

Communicable and non-communicable diseases

Communicable (infectious) diseases are caused by pathogens, so they can spread from one organism to another. Non-communicable diseases are not caused by pathogens and cannot be caught. They usually develop slowly and last a long time.

  • Measles, HIV and tobacco mosaic virus (viruses); Non-communicable Coronary heart disease
  • Salmonella food poisoning, gonorrhoea (bacteria); Non-communicable Type 2 diabetes
  • Malaria (protist); Non-communicable Most cancers
  • Rose black spot (fungus); Non-communicable Lung and liver diseases linked to smoking or alcohol

Exam tip: Ask: "Is a pathogen the cause?" If yes, the disease is communicable. A disease that lasts for life, such as HIV, can still be 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 late-stage HIV) make a person more likely to suffer from infectious diseases.
  • Viruses living inside cells can trigger changes that lead to cancer. Human papillomavirus (HPV) can trigger 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 serious 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 passed on by sexual contact. This is why young people in the UK are offered the HPV vaccine.

Using health data

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

Worked example: comparing two towns

In one winter, Town A (population 52 000) had 1638 cases of flu. Town B (population 140 000) had 3360 cases.
Town A: 1638 ÷ 52 000 × 100 = 3.15%. Rate = 1638 ÷ 52 000 × 100 000 = 3150 per 100 000.
Town B: 3360 ÷ 140 000 × 100 = 2.4%. Rate = 2400 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 (3150 per 100 000)

A scatter graph can show a correlation, for example between hours of exercise and days off sick. A correlation does not prove cause: another factor may affect both, or the pattern may be chance in a small sample. Scientists look for a mechanism (a biological explanation) and repeat studies with large samples.

Common mistakes

  • Saying health is "not being ill". It is physical and mental wellbeing.
  • Comparing numbers 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, not the cancer.
  • Calling every 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 statement best describes being healthy? (Choose from: Having no disease at all, Being in a state of physical and mental wellbeing, Being able to run a long way, Never needing to see a doctor.)

Answer: Being in a state of physical and mental wellbeing

Working: Health is a state of physical and mental wellbeing. A person with no disease can still be unhealthy, for example if they are very stressed or eat a poor diet.

Question 2. The scatter graph shows the mean hours of sleep per night and the number of colds caught in one year for 24 office workers. What does the graph show? (Choose from: A positive correlation: more sleep, more colds, A negative correlation: more sleep, fewer colds, No correlation, Proof that lack of sleep causes colds.)

Answer: A negative correlation: more sleep, fewer colds

Working: As hours of sleep increase, the number of colds falls, so it is a negative correlation. A correlation alone does not prove cause: another factor, such as stress, could affect both.

Question 3. True or false? Some viruses living inside cells can trigger changes that lead to cancer.

Answer: True

Working: True. Human papillomavirus (HPV) lives in cells and can trigger cervical cancer. The cancer itself cannot be caught, but the virus can be passed on.

Related lessons

Continue in the full course

This lesson is section B5.1 (AGCSC0501) of our free GCSE Combined Science 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 Combined Science course.

 

 

 

 

 

 

 

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