Tutopiya: Study Resources for IGCSE, IB, GCSE & A-Levels

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Practice — Communicable Diseases

1
Which of the following best defines a pathogen?
Answer & explanation
Correct: option B
AQA's spec definition: 'pathogen — a microorganism that causes an infectious disease'. Toxins are released by some pathogens but are not pathogens themselves.
2
How do bacteria typically cause symptoms of disease?
Answer & explanation
Correct: option C
Bacteria reproduce rapidly inside the body and release toxins; these damage tissues and cause symptoms. Option A is the viral mechanism.
3
Which of these is NOT one of the four pathogen groups named by AQA?
Answer & explanation
Correct: option D
AQA names bacteria, viruses, fungi and protists. Algae are not classed as a pathogen group on the spec.
4
Malaria is spread by the female Anopheles mosquito. The mosquito is best described as:
Answer & explanation
Correct: option C
A vector is an organism that carries a pathogen from one host to another. The mosquito itself isn't ill — it carries the protist that causes malaria.
5
Which strategy would best reduce the spread of an airborne viral infection in a school?
Answer & explanation
Correct: option B
Airborne droplet spread is interrupted by ventilation, masks and isolation of cases. The other options target waterborne, vector-borne and foodborne routes.
6
Why do bacteria cause symptoms so quickly after entering the body?
Answer & explanation
Correct: option B
Bacteria can double in number every ~20 minutes under ideal conditions, so toxin production quickly reaches the level needed to cause symptoms.
7
Which disease is NOT a communicable disease?
Answer & explanation
Correct: option C
Coronary heart disease is non-communicable — it is not caused by a pathogen. The other three are caused by a bacterium, virus and protist respectively.