AQA GCSE Combined Science Foundation (8464), Foundation tier · Biology › Infection and response › Communicable diseases
Practise Communicable (infectious) diseases. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
What pathogens are, the four types of pathogen, how they spread between animals and between plants, and how their spread can be reduced. On Paper 1 this comes up as short recall questions, 'explain how this disease is spread' questions and data on the number of cases of a disease.
Key facts
Pathogen = microorganism that causes infectious disease
Four types of pathogen: viruses, bacteria, fungi, protists
Communicable = can be passed from one organism to another
Spread by: direct contact, water, air (also food, body fluids, vectors)
Bacteria → toxins that damage tissues
Viruses → reproduce inside cells, damaging them
Vector = organism that carries a pathogen to a new host, e.g. mosquito
A pathogen is a microorganism that causes infectious disease. Diseases caused by pathogens are communicable: they can be passed from one organism to another.
There are four types of pathogen: viruses, bacteria, fungi and protists.
Pathogens can infect both animals and plants.
Non-communicable diseases, such as coronary heart disease, are not caused by pathogens, so they cannot be passed on.
How bacteria and viruses make you ill
diagram
Bacteria and viruses can reproduce rapidly inside the body, so their numbers rise quickly after infection.
Bacteria may produce poisons called toxins. Toxins damage tissues and make you feel ill.
Viruses live and reproduce inside your cells. This damages or destroys the cells.
Bacteria damage tissues with toxins; viruses destroy the cells they reproduce in.
How pathogens spread
Direct contact: touching an infected person or a contaminated surface, or sexual contact. Plants can be infected when an infected leaf touches a healthy one.
Water: drinking water or eating food washed in water that contains the pathogen. Water splashes can also carry pathogens between plants.
Air: breathing in droplets from an infected person's coughs and sneezes. Wind carries the spores of some plant pathogens.
Some pathogens are carried in food or in body fluids such as blood.
A vector is an organism that carries a pathogen from one host to another, e.g. mosquitoes carry the protist that causes malaria.
Reducing or preventing spread
Hygiene: washing hands, disinfecting surfaces and cooking food thoroughly remove or kill pathogens.
Isolating infected individuals stops them passing the pathogen on.
Destroying vectors, e.g. stopping mosquitoes breeding, means fewer pathogens are carried to new hosts.
Vaccination makes people immune, so they cannot be infected or pass the pathogen on.
In plants: remove and destroy infected leaves or plants, and use chemicals to kill the pathogens or the insects that carry them.
How to answer each type of question
Recall: define a pathogen and name the types
1 mark eachGrade 3
Learn the definition word for word: a microorganism that causes (infectious) disease.
Give exactly the number of answers asked for. An extra wrong answer can cancel a right one.
Example. (a) What is a pathogen? (b) Bacteria are one type of pathogen. Name two other types of pathogen.
Show the model answerHide the model answer
(a) A microorganism that causes (infectious) disease (1) (b) Any two from: viruses, fungi, protists (1) (1)
Explain how a disease is spread
2 marksGrade 4
Use the clues in the question, e.g. 'found in faeces' or 'carried by flies'.
Say how the pathogen leaves the infected person and how it reaches the next person.
Say how it gets into the new person: breathed in, swallowed, through the skin or by sexual contact.
Example. Cholera is a disease caused by a bacterium. The bacterium is found in the faeces of infected people. Explain how cholera can spread in an area without a clean water supply.
Show the model answerHide the model answer
Faeces containing the bacteria get into the water supply (1). Other people drink the water, or eat food washed in it, and swallow the bacteria (1).
Describe how bacteria and viruses cause illness
2 to 3 marksGrade 5
Say that both reproduce rapidly inside the body.
Bacteria: produce toxins that damage tissues.
Viruses: live and reproduce inside cells, damaging the cells.
Example. Bacteria and viruses can both cause disease. Describe how each type of pathogen damages the body.
Show the model answerHide the model answer
Both reproduce rapidly inside the body (1). Bacteria produce toxins (poisons) that damage tissues (1). Viruses live and reproduce inside cells, which damages the cells (1).
Don’t lose marks
Mixing up how bacteria and viruses cause harm: bacteria release toxins; viruses damage the cells they reproduce inside.
Writing 'germs' or 'bugs' instead of pathogen, bacterium or virus.
Giving a vague answer such as 'be hygienic' without saying what to do or how it stops the pathogen reaching a new host.
Calling the vector the pathogen: the mosquito carries the malaria pathogen, but the pathogen is a protist.
Thinking all microorganisms are pathogens. Most bacteria are harmless or useful; only those that cause disease are pathogens.
Three main routes: contact, water, air. Then add food, body fluids and vectors.
Match the control to the route: air → isolate and cover coughs; water → clean water; contact → hygiene; vector → kill the vector or avoid bites.
Bacteria make toxins; viruses wreck cells from the inside.
Exam technique
In 'explain how it spreads' answers, give the route and how the pathogen gets into the new person (breathed in, swallowed, through a cut, by sexual contact).
If the question describes a disease you have not met, use the information given rather than writing about a disease you know.
Show your working in percentage change calculations: the method mark is often given even if the final answer is wrong.
For 'suggest how to reduce spread', each method you explain is usually worth 2 marks: the method and how it works.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Define a pathogenA pathogen is a microorganism that causes infectious (communicable) disease.
Grade 3
Name the four types of pathogenViruses, bacteria, fungi and protists; they can infect both animals and plants.
Grade 4
Describe how pathogens are spreadBy direct contact, by water and by air, and also in food, in body fluids and by vectors.
Grade 5
Explain how bacteria and viruses make you illBoth reproduce rapidly in the body; bacteria release toxins that damage tissues, and viruses reproduce inside cells and damage them.
Grade 5
Describe ways to reduce the spread of diseaseHygiene, isolating infected individuals, destroying or controlling vectors, and vaccination.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Communicable diseases are caused by pathogens. What is a pathogen?
A microorganism that causes an infectious disease.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy6 marks
Communicable diseases are caused by pathogens.
(a) What is a pathogen?[1]
(b) Which list contains only types of pathogen? Tick (✓) one box.[1]
Antibodies, bacteria, fungi and viruses
Bacteria, fungi, protists and viruses
Bacteria, enzymes, protists and viruses
Bacteria, fungi, platelets and viruses
(c) Give two ways that pathogens can be spread from one organism to another.[2]
(d) Bacteria that reproduce inside the body can make a person feel ill. How do bacteria make a person feel ill?[1]
(e) How do viruses cause damage in the body?[1]
Show the answer and mark scheme
(a)Answer: A microorganism that causes an infectious disease.
a microorganism that causes (infectious / communicable) disease
(b)Answer: Bacteria, fungi, protists and viruses
(c)Answer: Any two from: direct contact, water, air, food, vectors, body fluids.
(by) direct contact
(by / in) water
(through the) air / in droplets from coughs and sneezes
(in) food
(by) vectors / animals such as insects
(through) body fluids / blood / sexual contact
(d)Answer: They produce toxins (poisons) that damage tissues.
(they) produce toxins / poisons (that damage tissues)
(e)Answer: They reproduce inside cells, which damages the cells.
(they) live and reproduce inside cells, damaging the cells
Question 2Medium6 marks
A stomach infection spread rapidly among 2400 passengers on a cruise ship. The pathogen is present in vomit and faeces, spreads by touching contaminated surfaces, and can survive outside the body for several days.
(a) Suggest two reasons why the infection spread so quickly among the passengers.[2]
(b) 312 of the 2400 passengers had symptoms. Calculate the percentage of passengers who had symptoms.[2]
(c) The crew closed the buffet and asked passengers to use alcohol hand gel before eating. Suggest two reasons why hand gel alone may not fully control the outbreak.[2]
Show the answer and mark scheme
(a)
many people live close together in a confined space, so there is a lot of close contact
many people touch the same surfaces, e.g. handrails and buffet equipment
the pathogen survives for several days outside the body, so surfaces stay contaminated
(b)Answer: 13%
312 ÷ 2400 × 100
13 (%)
(c)
hand gel cleans only hands, not contaminated surfaces or objects
passengers can pick up the pathogen again by touching contaminated surfaces after using the gel
infected passengers are still mixing with other passengers / are not isolated
the pathogen is also spread in vomit, not only on hands
some passengers may not use the gel, or may not use it properly / the gel may not kill this pathogen