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AS · Practice questions · Preventing and controlling infectious diseases

Name the measure, then weigh the factors.

Six original Cambridge-style questions on controlling infectious diseases, from why oral rehydration saves lives without stopping spread to why HIV still has no vaccine.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Answer a discuss question

Measure, factor, effect.

01
Recall
[3 marks]

State three ways of reducing the transmission of cholera.

  • Treat sewage so that faeces do not contaminate water supplies. ✓
  • Provide clean, piped or chlorinated (or boiled) drinking water. ✓
  • Hygiene: hand washing, and washing or cooking food in clean water; (also: oral vaccination). ✓
02
Explain
[4 marks]

Explain why it has proved very difficult to eradicate malaria.

  • Plasmodium has become resistant to many antimalarial drugs (such as chloroquine). ✓
  • Anopheles mosquitoes have become resistant to insecticides. ✓
  • The parasite spends time inside liver cells and red blood cells and changes its antigens, so the immune system and vaccines are only partly effective. ✓
  • Mosquitoes breed in any small area of standing water, and many affected countries cannot afford large control programmes; people may not use nets consistently. ✓
03
Explain
[4 marks]

Suggest why the control of TB in a country is harder when a large proportion of the population is infected with HIV.

  • HIV destroys T-helper cells, so the immune system is weakened. ✓
  • People with HIV are more likely to be infected with TB and to develop active TB. ✓
  • More people with active TB means more bacteria released in droplets, so more transmission. ✓
  • Treating patients for both diseases at once is more complex and costly. ✓
04
Analysis
[4 marks]

Discuss the social and economic factors that need to be considered in the control of HIV/AIDS.

  • Social: stigma may stop people being tested or telling partners, so they continue to transmit HIV unknowingly. ✓
  • Social: cultural or religious attitudes may reduce condom use; education campaigns are needed. ✓
  • Economic: antiretroviral drugs must be taken for life and are expensive for poor countries (though costs have fallen). ✓
  • Economic: illness and death of working-age adults reduces income, leaves orphans and harms the national economy. ✓
05
Recall
[2 marks]

State what is meant by DOTS in the treatment of TB and give one reason for using it.

  • Directly observed treatment, short course: a health worker watches the patient take each dose of the drugs. ✓
  • It makes sure the whole course is completed, so the infection is cured and drug-resistant strains are less likely to develop. ✓
06
Data
[3 marks]

In the lab's outbreak model for malaria, ticking insecticide-treated bed nets alone gives a smaller outbreak, and ticking bed nets together with antimalarial drugs stops the outbreak almost at once. Explain why the combination is more effective than either measure alone.

  • Bed nets reduce the number of bites, so fewer new people are infected by each infected person. ✓
  • Antimalarial drugs cure infected people sooner, so each person is infectious to mosquitoes for a shorter time. ✓
  • Together the average number of new cases per infected person falls below one, so the outbreak dies out. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.