Why stopping TB medicine early is a population problem
A health volunteer in a settlement of 600 people follows 15 patients on tuberculosis treatment. After two months, 6 stop coming because their cough has gone and they feel strong. Three of those 6 return five months later with worse symptoms; one is confirmed to have drug-resistant TB. The volunteer has a small budget and argues that buying food supplements will encourage attendance more than directly observed treatment (DOT), where a volunteer watches each patient swallow the tablets. The clinic is a 90-minute walk away. Patients say the tablets make them feel sick and that they cannot afford bus fare. The volunteer asks whether the 3 relapses are a big enough problem to change the whole programme. The settlement has one small shop and crowded houses, with eight to ten people sleeping in some rooms.
1. Explain, using variation and selection, why stopping treatment early can lead to drug-resistant TB. Why is this not simply the patient's fault?
Read the worked answer
TB bacteria in a patient are not all identical; some are slightly less affected by the drugs. Early in treatment, the drugs kill the weakest bacteria, and the patient feels better. If treatment stops after two months, the tougher survivors remain. They multiply, and the patient relapses with a population that is more resistant. Repeated stopping and starting selects for resistance.
It is not simply the patient's fault. The tablets cause nausea, the clinic is a 90-minute walk, and bus fare is unaffordable. In a crowded house, one infectious person can pass TB to others. The programme must make it easier to complete treatment, not just blame patients. In this group, 6 of 15 stopped, which is 40%, and 3 of those 6 relapsed, which is 50% of the stoppers.
2. Evaluate the volunteer's plan to spend the small budget on food supplements instead of DOT. Recommend a combined approach with practical steps.
Read the worked answer
Food supplements alone may improve attendance but do not guarantee that tablets are swallowed. DOT guarantees observation, but it is hard when the clinic is far away. The best approach combines both.
Practical steps:
- Train a nearby community volunteer to observe each dose at a fixed time, so patients do not travel to the clinic daily.
- Manage side effects: give tablets with food, refer severe nausea, and explain that feeling better does not mean cured.
- Use food supplements as an incentive for attendance, not as a substitute for observation.
- Trace defaulters quickly and test close contacts.
With 40% interruption, the current programme is already failing. A combined plan targets the real barriers and protects the whole settlement.
3. The volunteer says, 'Only 3 came back, so the problem is small.' Evaluate this claim using the numbers and the risk of transmission in crowded housing.
Read the worked answer
The claim is misleading. Three of the 6 who stopped relapsed, which is 50% of the stoppers, and 3 of 15 patients is 20% of the whole group. Those are high proportions, not small ones. Also, the 3 who returned are only the ones who came back; others may have moved away or died without being counted.
TB spreads through the air in crowded rooms. An untreated infectious person can infect many others over months, and one drug-resistant case is much harder and more expensive to treat. In a settlement of 600 people, one resistant case is a serious public-health warning. Small absolute numbers do not mean low risk; they mean the programme is losing patients early and must change.