Community Health and Environmental Sanitation: Prevention and Safe Water
What this domain tests
Community Health and Environmental Sanitation tests prevention levels, disease frequency measures, safe water, waste disposal, vector control and sanitation indicators. Calculations of rates are common.
Core rules
- Primary prevention acts before disease (immunisation, health education, safe water). Secondary prevention detects early disease (screening, case finding). Tertiary prevention limits disability and rehabilitates.
- Incidence = new cases in a period ÷ population at risk × 100. Prevalence = all existing cases at a point or period ÷ total population × 100.
- Safe water: protect the source, chlorinate, and check residual free chlorine (about 0.5 mg/L at the tap). Boiling at sea level for 1 minute kills most pathogens.
- Sanitation: use sanitary latrines, wash hands with soap after defecation and before food, and segregate biodegradable and non-biodegradable waste.
- Vector control: eliminate stagnant water, cover containers, use larvivorous fish and insecticide-treated nets where appropriate.
Worked example
In a village of 2,000 people, 80 new diarrhoea cases occur in one week. Reasoning: attack rate = 80 ÷ 2,000 × 100 = 4%. Investigate the water source, check chlorination and storage, start oral rehydration for cases, refer severe dehydration, and teach hand hygiene and safe water practices. Do not assume all diarrhoea needs antibiotics; most acute cases are viral or self-limiting.
Traps
- Using total population instead of population at risk for incidence.
- Confusing incidence with prevalence.
- Saying boiling for a few seconds is enough at sea level; bring to a rolling boil for 1 minute.
- Ignoring residual chlorine after storage.