Practise 36 real questions on Infectious diseases from 2021 to 2026. See the answer and explanation as soon as you answer.
Infectious diseases is one of the 11 main topics in our A Level Biology (Cambridge (CAIE) 9700) question bank, and about 5% of its real questions come from it. Tayyari Karo has 36 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2; 28 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 24 medium, 7 hard, 5 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
What increases the risk of contracting TB?
1 drinking unpasteurised milk
2 eating shellfish which have been contaminated with faeces
3 living in overcrowded conditions
Answer: B. 1 and 3
Bovine TB spreads in unpasteurised milk and TB spreads by droplets in overcrowded conditions.
Which statements explain why cholera has not been eradicated by vaccination?
1 There is limited availability of an affordable vaccine.
2 Protection takes several weeks to develop after vaccination.
3 The under-reporting of cholera in the community.
4 Immunity to cholera decreases after two years.
Answer: A. 1, 2, 3 and 4
Limited vaccine availability, delayed onset of protection, under-reporting of cases, and declining immunity after around two years all contribute to cholera not being eradicated by vaccination, so all four statements are correct.
How does penicillin affect bacteria?
Answer: C. It is a competitive inhibitor of an enzyme in cell wall synthesis.
Penicillin competitively inhibits the transpeptidase enzyme involved in cross-linking peptidoglycan during bacterial cell wall synthesis.
Whooping cough is a highly infectious disease of the gas exchange system, caused by the bacterium Bordetella pertussis.
Which method provides protection to infants against whooping cough and reduces the chance of developing this disease later?
Answer: D. injections of antigens from Bordetella pertussis bacteria
Vaccination with antigens from Bordetella pertussis stimulates active immunity (memory cell production), giving lasting protection, unlike antibiotics or a passive dose of ready-made antibodies.
Some of the processes which result in the formation of a population of bacteria that are resistant to a new antibiotic are listed: 1 change in reproductive success of bacteria, 2 increase in frequency of the resistance allele in the population, 3 increase in genetic variation within the population, 4 random mutation occurs in bacterial DNA. What is the correct order of these processes?
Answer: D. 4 → 3 → 1 → 2
A random mutation occurs in bacterial DNA (4), increasing genetic variation within the population (3), giving resistant bacteria a change in reproductive success/survival advantage (1) when exposed to the antibiotic, leading to an increase in the frequency of the resistance allele in the population (2) — order 4→3→1→2.
Which disease is caused by a eukaryote?
Answer: B. malaria
Malaria is caused by Plasmodium, a eukaryotic protoctist; cholera is caused by a bacterium (Vibrio cholerae), while measles and smallpox are caused by viruses.
| Session | Paper 1 | Paper 2 |
|---|---|---|
| May/June 2026 | 2 | 1 |
| May/June 2025 | 4 | – |
| October/November 2025 | 3 | 1 |
| May/June 2024 | 4 | 1 |
| October/November 2024 | 2 | 1 |
| May/June 2023 | 3 | – |
| October/November 2023 | 2 | 1 |
| May/June 2022 | 1 | 1 |
| October/November 2022 | 1 | – |
| May/June 2021 | 3 | 1 |
| October/November 2021 | 3 | 1 |
36 real A Level Biology (9700) questions on Infectious diseases from 2021 to 2026, from Paper 1, Paper 2. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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