Communicable and Non-communicable Diseases: Transmission and Prevention
What this domain tests
This domain covers communicable disease transmission and control, plus major non-communicable diseases and their risk factors. The exam often asks about mode of spread, prevention, warning signs and false beliefs.
Core rules
- Communicable disease chain: infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, susceptible host. Break one link to prevent spread.
- Tuberculosis spreads by airborne droplet nuclei; it is not spread by sharing food. BCG protects mainly against severe childhood TB, not adult pulmonary TB.
- Malaria is transmitted by the bite of the female Anopheles mosquito; dengue by Aedes aegypti, which bites mainly by day and breeds in clean stagnant water.
- HIV spreads through unprotected sex, infected blood and mother-to-child transmission; it is not spread by hugging, sharing food or mosquito bites.
- Non-communicable diseases include diabetes, hypertension, cardiovascular disease, cancer and chronic lung disease. Shared risk factors: tobacco, alcohol, unhealthy diet, physical inactivity and obesity.
- Hypertension is often asymptomatic; measure BP rather than relying on symptoms.
Worked example
A student has high fever, severe headache, muscle pain and a rash, and his village has stored water in open containers. Dengue is suspected. Reasoning: day-biting Aedes mosquitoes breed in clean stored water, so search and destroy larval sites, cover containers and use repellent. Avoid aspirin and ibuprofen because of bleeding risk; give paracetamol only as advised. Monitor for warning signs such as bleeding gums, persistent vomiting, abdominal pain and drowsiness, and refer urgently.
Traps
- Saying TB spreads through food or touch.
- Confusing malaria and dengue vectors.
- Assuming a person with hypertension must feel unwell.
- Advising antibiotics for viral infections.