Practise Communicable (infectious) diseases. 12 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.
Grade by grade
What you need to be able to do, from the first marks up to the top grade.
3
Define a pathogenA pathogen is a microorganism that causes infectious (communicable) disease.
3
Name the four types of pathogenViruses, bacteria, fungi and protists; they can infect both animals and plants.
4
Describe how pathogens are spreadBy direct contact, by water and by air, and also in food, in body fluids and by vectors.
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.
5
Describe ways to reduce the spread of diseaseHygiene, isolating infected individuals, destroying or controlling vectors, and vaccination.
6
Explain how a control method stops spreadLink the method to the route, e.g. washing hands removes pathogens, so they are not passed on by direct contact.
7
Interpret data on the spread of a diseaseDescribe trends in case numbers, calculate percentage changes and use the way the pathogen spreads to explain the pattern.
Notes
Pathogens
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
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.
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.
Cheatsheet
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
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 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 marks4
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 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 marks5
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 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).
Suggest and explain ways to reduce spread
2 to 4 marks6
Pick methods that match the way this pathogen spreads.
For each method, give the method (1 mark) and explain how it stops the pathogen reaching a new host (1 mark).
Example. An outbreak of a disease has started on a hospital ward. The disease is caused by a bacterium that is spread by direct contact. Suggest two ways staff could reduce the spread of the disease. Explain how each way works.
Show the model answer
Wash hands or use hand gel between patients (1), which removes or kills the bacteria so they are not carried to the next patient (1). Isolate infected patients in a separate room (1), so that other patients cannot come into contact with them (1). Also allow: disinfect surfaces, so bacteria on them are killed; wear disposable gloves and aprons.
Data: numbers of cases
2 to 3 marks7
Percentage change = change ÷ original value × 100.
Show the subtraction and the division: each is usually a mark.
When asked for a reason, use the way the pathogen spreads.
Example. There were 60 cases of a disease in a town in week 1 and 150 cases in week 4. (a) Calculate the percentage increase in the number of cases. (b) The disease is spread in droplets from coughs and sneezes. Suggest why the number of cases increased quickly.
Show the model answer
(a) 150 − 60 = 90 (1); 90 ÷ 60 × 100 = 150% (1) (b) Each infected person coughs and sneezes out droplets, which can be breathed in by several other people nearby (1).
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.
Where marks are lost
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.
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.
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.
What name is given to an organism, such as the midge, that carries a pathogen from one organism to another?
Vector
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
Question 3Hard8 marks
Bluetongue is a disease of sheep and cattle. It is caused by a virus. The virus is carried from one animal to another by small biting insects called midges. It is not usually spread by direct contact between animals. Midges breed in wet mud and animal dung. They are most active around dusk and dawn.
(a) What name is given to an organism, such as the midge, that carries a pathogen from one organism to another?[1]
(b) Farmers are given this advice to reduce the spread of bluetongue:
keep animals indoors from dusk until dawn
treat animals with an insecticide
move animals away from wet, muddy fields.
Explain how each piece of advice reduces the spread of bluetongue.[3]
(c) A farmer moved infected sheep into a separate field, away from the healthy sheep. The disease still spread to the healthy sheep. Suggest why moving the infected sheep did not stop the spread.[2]
(d) Vaccines against bluetongue are available. Explain why vaccinating most of the sheep on a farm also helps to protect the sheep that have not been vaccinated.[2]
Show the answer and mark scheme
(a)Answer: Vector
vector
(b)
(indoors) animals are bitten less often when the midges are most active
insecticide kills the midges / vectors (so fewer animals are bitten)
fewer midges breed / live near the animals (away from wet mud)
(c)
midges can fly from one field to another
(so) a midge can pick up the virus from an infected sheep and pass it to a healthy sheep
(d)
vaccinated sheep do not become infected / do not carry the virus
(so) fewer midges pick up the virus, so an unvaccinated sheep is less likely to be bitten by an infected midge