CM8.1-7 | Disease Epidemiology and Control — Graded Quiz

Correct. Falciparum malaria at PHC = ACT + single-dose primaquine per NVBDCP protocol.

Multiple ring forms per RBC + appliqué (accolé) appearance = Plasmodium falciparum. NVBDCP protocol for uncomplicated P. falciparum: ACT (artesunate 4 mg/kg/day × 3 days + SP on Day 1) + single-dose primaquine 0.75 mg/kg for gametocyte clearance. Chloroquine is for vivax (CQ-sensitive). IV quinine is for severe/complicated falciparum, not uncomplicated PHC cases.

Multiple ring forms + appliqué appearance = P. falciparum. NVBDCP mandates ACT (not chloroquine) for falciparum. Chloroquine is reserved for P. vivax.

Correct. AR = (80/400) × 100 = 20%. The denominator is feast attendees (the population at risk), not the total village.

Attack rate = (Cases ÷ Population at risk) × 100 = (80 ÷ 400) × 100 = 20%. The denominator is the population at risk (feast attendees = 400), NOT the total village population (2,000). Using 2,000 gives 4% — a common error. Using 80/200 or 80/100 reflects misidentification of the denominator.

Attack rate uses the exposed (at-risk) population as the denominator, not the total village population. AR = 80/400 × 100 = 20%.

Correct. Active surveillance = regular S-form submission with seasonally plausible (non-universal zero) patterns.

Active surveillance is characterised by regular reporting (S-forms submitted every week) with biologically plausible patterns — diarrhoea peaks in monsoon, ARI in winter. Perpetual zero-reporting without seasonal variation signals passive or absent surveillance. HMIS immunisation data reflects vaccination performance, not surveillance quality. Absence of L-form data may reflect no lab capacity, not good health.

High-quality surveillance shows regular reporting with biologically plausible patterns. Perpetual zeros or absence of L-forms are red flags, not quality indicators.

Correct. Step 1 of outbreak investigation = verify diagnosis. All subsequent steps depend on this confirmation.

The 10-step outbreak investigation framework begins with verifying the diagnosis (Step 1) — confirming that cases meet the case definition (clinical criteria + NS1 antigen/serology for dengue). Only after diagnosis is confirmed can you establish case definitions, count cases, draw the epidemic curve, and implement specific control measures. Acting on an unconfirmed diagnosis wastes resources and may miss the true pathogen.

In outbreak investigation, verify diagnosis first before counting cases, drawing curves, or implementing control. Acting before confirmation risks chasing the wrong pathogen.

Correct. ASHAs submit S-forms (syndromic clusters) weekly from their household rounds — this is their primary surveillance contribution.

In IDSP: S-form (Syndromic surveillance) is the community-level form submitted by ASHAs, AWWs, and community health workers — they report syndromes (not diagnoses). P-form is for PHC/CHC doctors (presumptive diagnoses). L-form is for laboratories. All forms flow upward: sub-centre → PHC → district → state → national. There is no direct bypass to state/national.

IDSP form assignment: ASHA = S-form (syndromes); PHC doctor = P-form (presumptive); Lab = L-form (confirmed). Forms travel up the chain, not directly to state.

Correct. NPCDCS PHC screening = BP + RBG + clinical breast/oral/cervical examination — simple, low-cost, done at every visit.

NPCDCS PHC-level opportunistic screening for adults ≥30 years: (1) Blood pressure measurement, (2) Random blood glucose (or fasting glucose), (3) Clinical breast examination (women), (4) Oral cavity examination, (5) Cervical inspection (VIA/VILI for women). This is done opportunistically at every PHC visit. CT, colonoscopy, mammography, and spirometry are tertiary/secondary-level investigations not provided at PHC.

NPCDCS PHC screening uses basic clinical tools (BP, RBG, clinical examination) — no imaging or invasive tests. Opportunistic screening at every visit, not annual camps only.

Correct. Susceptible cohort accumulation in under-vaccinated pockets is the dominant mechanism for measles resurgence in high-coverage districts.

95% coverage at district level can mask micro-pockets with lower coverage (e.g. urban slums, nomadic populations, minority communities). Over time, susceptible cohorts accumulate in these pockets. When density reaches critical mass, the herd immunity threshold (>95% for measles, R0=12-18) is breached locally and outbreaks occur. This is the 'cohort accumulation' mechanism underlying resurgent measles even in high-coverage districts. Cold chain failure causes vaccine potency loss but typically < 50% efficacy drop. Measles wild-type virus has not shown clinically meaningful vaccine-escape mutations.

District-level coverage figures mask sub-district heterogeneity. Susceptible cohort accumulation in under-vaccinated pockets breaches the local herd immunity threshold — not cold chain failure or viral mutation.

Correct. HIT = 1 − 1/R0 = 1 − 0.25 = 75% when R0 = 4.

Herd immunity threshold (HIT) = 1 − (1/R0). For R0 = 4: HIT = 1 − (1/4) = 1 − 0.25 = 0.75 = 75%. Below this threshold, each infected person still generates >1 new case on average (Reff > 1) and the epidemic continues. This formula is fundamental to vaccine coverage target-setting at national programme level.

Use the formula: Herd Immunity Threshold = 1 − (1/R0). With R0 = 4: HIT = 1 − 1/4 = 75%.

Correct. Targeted training using the deficient forms + verification at the next cycle is the evidence-based supervisory response.

PHC physician's role in surveillance training (CM8.6): Surveillance quality problems are primarily education gaps, not motivational failures at first instance. The correct response is capacity-building — targeted training using actual deficient forms as teaching material — followed by supervised verification at the next reporting cycle. Punitive measures (warnings, transfers) before education destroy trust and worsen reporting. Fabricating data is a serious ethical violation.

Surveillance training is the first-line response to incomplete reporting. Punitive action and data fabrication are ethically and operationally harmful.

Correct. HPV vaccination (primary) + VIA/VILI (secondary) + cryotherapy/LEEP+referral (tertiary) is the NPCDCS cervical cancer prevention cascade.

Cervical cancer under NPCDCS: Primary prevention = HPV vaccination (Girls 9-14 years under UIP/school programme) + health education on risk factors (tobacco, delayed first sexual contact). Secondary prevention = VIA (Visual Inspection with Acetic Acid)/VILI screening at PHC (simple, low-cost) for women 30-60 years. Tertiary prevention = cryotherapy/LEEP at PHC/CHC for CIN lesions + referral for invasive cancer to district hospital. Pap smear every 3 years is not the current NPCDCS protocol at PHC level; radical hysterectomy is not a PHC procedure.

NPCDCS cervical cancer protocol: HPV vaccine = primary prevention; VIA/VILI at PHC = secondary; cryotherapy/LEEP + referral = tertiary. Pap smear is NOT the PHC-level screening method in NPCDCS.