Public Health & Epidemiology — Advanced Nursing Guide

Epidemiology Measures Quick Reference ▼

Measure	Formula	Key Point
Incidence Rate	New cases / Person-time at risk	Measures speed of disease occurrence
Cumulative Incidence	New cases / Population at risk (fixed period)	Risk / attack rate
Prevalence	All cases / Total population	Point or period; useful for chronic disease burden
Crude Death Rate	Deaths / Mid-year population × 1,000	Unadjusted; affected by age structure
CFR	Deaths from disease / Cases of disease × 100	Severity indicator
MMR	Maternal deaths / 100,000 live births	Key maternal health indicator
IMR	Infant deaths <1yr / 1,000 live births	Proxy for development
Relative Risk (RR)	Incidence exposed / Incidence unexposed	Cohort studies; >1 = increased risk
Odds Ratio (OR)	(a/c) / (b/d)	Case-control; approximates RR when prevalence <10%
AR%	(RR−1)/RR × 100	Fraction of disease attributable to exposure
NNT	1 / ARR	Patients treated to prevent 1 outcome
NNH	1 / ARI	Patients treated before 1 harm occurs

Disease Measurement

Incidence vs Prevalence

Incidence: NEW cases in a defined period — measures disease risk. Used for acute conditions.

Prevalence: ALL existing cases at a point in time — measures disease burden. Used for chronic conditions & planning.

Prevalence ≈ Incidence × Duration (steady state)

Mortality & Morbidity

Mortality rate: frequency of death in a population
Morbidity rate: frequency of illness/disability
DALY: Disability-Adjusted Life Year = YLL + YLD
QALY: Quality-Adjusted Life Year (used in health economics)

Rates & Ratios

Types of Rates

Crude rate: whole population denominator; affected by age structure — misleading for comparisons
Age-specific rate: calculated within age bands; removes age confounding
Age-standardised rate: uses standard population weights — enables valid comparisons across populations
Direct standardisation: apply study population rates to standard population
Indirect standardisation: calculate SMR (Observed/Expected × 100)

SMR > 100 = more deaths than expected; < 100 = fewer

Study Designs

Experimental

RCT: Gold standard. Random allocation, controls confounding, establishes causality. Highest internal validity.

CausalityIntervention

Observational — Analytic

Cohort: Follow exposed/unexposed forward in time. Calculates RR. Best for rare exposures.

Case-control: Compare cases & controls retrospectively. Calculates OR. Best for rare diseases.

Cross-sectional: Snapshot in time. Calculates prevalence. Cannot establish temporality.

Observational

Descriptive & Other

Ecological: Group-level data; subject to ecological fallacy (group associations ≠ individual).

Case series/report: Hypothesis-generating; no comparison group.

Systematic review/meta-analysis: Highest level of evidence hierarchy.

Evidence synthesis

Study Type	Direction	Measure	Best For	Key Weakness
RCT	Prospective	RR, ARR, NNT	Intervention efficacy	Cost, ethics, generalisability
Cohort	Prospective	RR, IR	Rare exposures	Loss to follow-up, expensive
Case-control	Retrospective	OR	Rare diseases	Recall bias, selection bias
Cross-sectional	Single point	Prevalence, PR	Burden estimation	No temporality, survivor bias
Ecological	Any	Correlation	Hypothesis generation	Ecological fallacy

Bias Types

Selection Bias

Systematic difference in who is selected. Types: Berkson bias (hospital-based controls), Healthy worker effect, Survivor bias, Non-response bias.

Information / Measurement Bias

Recall bias: Cases recall past exposures differently than controls (case-control).

Observer bias: Researcher records data differently based on group.

Interviewer bias: Researcher probes differently between groups.

Confounding

Third variable associated with both exposure and outcome — distorts true relationship. Prevention: randomisation, restriction, matching, stratification, multivariable analysis.

Confounding can be controlled; bias cannot be corrected after data collection.

Screening Criteria (Wilson & Jungner)

Condition is an important health problem
Natural history of condition is well understood
Recognisable latent or early symptomatic stage exists
Suitable test or examination available
Accepted treatment for recognised disease
Agreed policy on whom to treat
Test acceptable to the population
Facilities for diagnosis & treatment available
Cost is balanced against expenditure as a whole
Case-finding is a continuing process

Sensitivity, Specificity, PPV & NPV

	Disease +	Disease −
Test +	TP (a)	FP (b)
Test −	FN (c)	TN (d)

Sensitivity = a / (a+c) — "SnNout"

Specificity = d / (b+d) — "SpPin"

PPV = a / (a+b) ← affected by prevalence

NPV = d / (c+d) ← affected by prevalence

LR+ = Sensitivity / (1−Specificity)

LR− = (1−Sensitivity) / Specificity

LR+ >10 Strong evidence to rule IN

LR− <0.1 Strong evidence to rule OUT

Key principle: High sensitivity = few false negatives (good for rule-out). High specificity = few false positives (good for rule-in). PPV rises with prevalence; NPV falls with prevalence.

Screening Test Analyser

Sensitivity (%)

Specificity (%)

Disease Prevalence (%)

Prevention Levels

Primary: Prevent disease onset. Immunisation, health education, water fluoridation, seat belts, HPV vaccination.

Secondary: Early detection & treatment to halt progression. Screening programmes, case-finding, treatment of hypertension.

Tertiary: Reduce complications & disability. Cardiac rehabilitation, diabetes foot care, palliative care.

Primordial: Prevent risk factors from emerging in the first place. Policy-level — taxation on tobacco, trans-fat bans.

NCD Risk Factors (WHO)

Modifiable Behavioural

Tobacco use: smoking & smokeless; 8M deaths/yr globally
Harmful alcohol use: 3M deaths/yr
Physical inactivity: 4th leading global mortality risk
Unhealthy diet: excess salt/sugar/saturated fat; low fruit/veg

Metabolic Risk Factors

Raised blood pressure (>130/80 mmHg)
Overweight/obesity (BMI ≥25/≥30)
Hyperglycaemia (FPG ≥7 mmol/L)
Hyperlipidaemia (LDL >3 mmol/L)

WHO MPOWER Framework

Six evidence-based tobacco control policies:

M — Monitor tobacco use & prevention policies
P — Protect people from tobacco smoke (smoke-free laws)
O — Offer help to quit tobacco use
W — Warn about the dangers of tobacco (graphic labels)
E — Enforce bans on advertising, promotion & sponsorship
R — Raise taxes on tobacco products

Tax increases are the single most effective tobacco control measure.

Brief Intervention — ABC Model

Used in primary care and nursing practice for tobacco, alcohol, and other health behaviours:

A — Ask: Screen all patients; record smoking/alcohol status in notes
B — Brief advice: Clear, personalised, non-judgmental advice to change (30 seconds suffices)
C — Cessation support: Refer to specialist services; offer NRT, varenicline, bupropion; follow-up

Even 3-minute advice from a nurse doubles quit rates vs no advice.

AUDIT-C (Alcohol Screening)

3-question tool: frequency, quantity, binge frequency. Score ≥5 (men) or ≥4 (women) = hazardous use.

Cancer Screening Programmes

Cancer	Test	Target Group	Interval
Breast	Mammography	Women 50–70	Every 3 yrs (UK); 2 yrs (US)
Cervical	HPV DNA + cytology	Women 25–64	Every 5 yrs (HPV primary)
Colorectal	FIT / colonoscopy	50–74 yrs	Annual FIT or 10-yr scope
Prostate	PSA (informed choice)	Men ≥50	Not routine; after discussion
Diabetic retinopathy	Digital photography	All T1/T2 DM	Annual

Cardiovascular Risk Assessment

QRISK3: UK tool predicting 10-year CVD risk. Includes: age, sex, ethnicity, smoking, systolic BP, cholesterol ratio, BMI, deprivation, diabetes, family history, AF, CKD, SLE, severe mental illness, erectile dysfunction, systolic BP variability.

Framingham: Classic US tool; 10-year CHD risk. Includes: age, total cholesterol, HDL, systolic BP, treatment status, smoking, diabetes.

Treatment threshold: QRISK3 ≥10% → offer statin. ≥20% = high risk.

QRISK3 performs better in South Asian and Black populations than Framingham.

Population vs Individual Interventions

Population-Level (Upstream)

Legislation (seat belt laws, food labelling mandates)
Taxation (sugar-sweetened beverage tax, tobacco tax)
Environmental modification (cycle lanes, smoke-free spaces)
Mass media campaigns
Fortification (folate in flour, iodine in salt)

Individual-Level (Downstream)

Clinical screening and counselling
Pharmacotherapy (statins, NRT)
Behaviour change interventions

Prevention paradox (Rose): A measure that brings large benefit to population brings little to each individual.

Health in All Policies (HiAP)

An approach to public policies across sectors that systematically takes into account the health implications of decisions. Recognises that health is determined by sectors outside health (transport, housing, education, food, environment).

Urban planning affects physical activity and air quality
Education policy affects health literacy and life expectancy
Agriculture policy affects diet and obesity rates

Used in Finland, South Australia, WHO advocacy
Requires intersectoral collaboration and shared accountability
Health Impact Assessment (HIA) is a key HiAP tool

Outbreak Investigation Steps ▼

Confirm the diagnosis (laboratory confirmation)
Establish case definition (clinical + epidemiological criteria)
Case-finding — active surveillance, line listing
Describe in terms of person, place, time (epidemic curve)
Generate hypotheses about source and transmission
Test hypotheses (analytic study — cohort or case-control)
Implement control and prevention measures
Communicate findings to authorities and public
Write a final report

Attack Rate = (Cases / Population at risk) × 100

Secondary Attack Rate = New cases in contacts / Susceptible contacts × 100

Notifiable Diseases Framework

Statutory requirement to notify public health authorities. Enables surveillance, outbreak detection, and response.

Examples (UAE/International)

Cholera, plague, yellow fever (IHR 2005 core)
COVID-19 (PHEIC declared 2020)
Meningococcal disease, typhoid, MERS-CoV
TB, HIV, hepatitis A/B/C
Measles, mumps, rubella
Foodborne outbreaks (≥2 related cases)

IHR 2005 requires notification to WHO within 24 hours of PHEIC-qualifying events.

Epidemic Curve Shapes

Point source: Sharp rise, rapid fall within one incubation period. Suggests common source (food, water) at single time.

Propagated: Multiple peaks, each separated by one incubation period. Suggests person-to-person spread.

Continuous common source: Gradual rise and sustained plateau. Ongoing exposure (contaminated water supply).

Mixed: Starts as point source, then propagated secondary transmission.

The shape of the epidemic curve guides the investigation and control strategy.

Contact Tracing & Quarantine vs Isolation

Contact Tracing Principles

Identify all exposed contacts within infectious window
Notify contacts — inform without revealing index case identity
Assess exposure level (close contact definition varies by pathogen)
Offer testing, prophylaxis, or quarantine as appropriate
Forward contact tracing (who was exposed by case)
Backward tracing (who exposed the case)

	Quarantine	Isolation
Applied to	Exposed but not yet ill (potential cases)	Confirmed or probable cases
Basis	Precautionary (may be infected)	Confirmed infectious period
Duration	Maximum incubation period of pathogen	Until no longer infectious
Legal basis	Public health law	Public health law

Herd Immunity & R Number

Basic Reproduction Number (R₀): Average number of secondary cases generated by one case in a fully susceptible population. Inherent property of pathogen + context.

Herd Immunity Threshold = 1 − (1 / R₀)

Disease	R₀	Herd Immunity %
Measles	12–18	92–95%
Polio	5–7	80–86%
COVID-19 (original)	2–3	50–67%
COVID-19 (Omicron)	8–15	88–93%
Influenza	2–4	50–75%

Effective R (R_t): Real-time R accounting for immunity in population. R_t < 1 = epidemic declining.

PPE Hierarchy of Controls

🚫

1. Elimination

Remove the hazard entirely. Most effective. E.g., cancel elective procedures during outbreak.

🔄

2. Substitution

Replace hazardous agent with safer alternative. E.g., use less virulent organism in teaching.

🏛

3. Engineering Controls

Physical barriers: negative pressure rooms, HEPA filtration, laminar flow hoods, partitions.

📋

4. Administrative Controls

Policies & procedures: cohorting patients, staff training, hand hygiene protocols, shift patterns.

👓

5. PPE

Last line of defence: gloves, aprons, surgical masks, FFP2/3, eye protection, gowns. Least effective alone.

Standard Precautions

Hand hygiene (5 moments), PPE use, safe injection practice, respiratory hygiene, safe waste disposal, environmental cleaning.

Surveillance Systems

Passive Surveillance

Healthcare providers report cases to authorities as routine. Low cost but under-reporting is major limitation. Used for notifiable diseases.

Active Surveillance

Health authorities actively seek out cases (phone calls, site visits). More complete but resource-intensive. Used during outbreaks.

Sentinel Surveillance

Selected sites/providers report on specific conditions. Cost-effective for monitoring trends. E.g., influenza-like illness from GP network. Cannot estimate true burden.

System	Examples	Advantage
Passive	Notifiable disease reporting	Low cost, wide coverage
Active	WHO polio eradication surveillance	Completeness, timely detection
Sentinel	FLUNET, syndromic surveillance	Efficiency, trend monitoring
Syndromic	ED chief complaint surveillance	Early warning, near-real-time

Ottawa Charter Action Areas ▼

1. Build Healthy Public Policy

Put health on the agenda of policy makers in all sectors and at all levels. Tobacco legislation, food safety standards, planning policy.

2. Create Supportive Environments

Physical, social, economic, and political environments that are health-promoting. Safe workplaces, clean air, cycle-friendly cities.

3. Strengthen Community Action

Empower communities to set priorities, make decisions, and take action. Community development, participatory approaches.

4. Develop Personal Skills

Health education, skill development, and information to help people make healthier choices. Life skills, self-management programmes.

5. Reorient Health Services

Move health services beyond clinical care toward health promotion. Multi-disciplinary teams, preventive focus, patient-centred care.

Ottawa Charter (1986)

WHO landmark document defining health promotion. Health = "a resource for everyday life, not the object of living." Prerequistes: peace, shelter, education, food, income, stable ecosystem.

Social Determinants of Health

Dahlgren-Whitehead Model (1991) — layers of influence on health:

Core: Age, sex, constitutional factors (non-modifiable)
Individual lifestyle factors: Diet, smoking, physical activity
Social & community networks: Social support, community cohesion
Living & working conditions: Housing, education, employment, healthcare, food production
Socio-economic, cultural, environmental conditions: Poverty, globalisation, climate

Marmot Review (2010): Social gradient in health — higher socioeconomic position = better health outcomes at every step.

Health Inequalities

Systematic, avoidable, and unfair differences in health outcomes between groups defined by socioeconomic status, ethnicity, geography, gender, disability, or other characteristics.

Causes

Income and wealth inequality
Educational disadvantage
Occupational hazards and unemployment
Housing conditions and overcrowding
Healthcare access and quality
Racism and discrimination

Measurement

Slope Index of Inequality (SII): Absolute measure across deprivation range
Relative Index of Inequality (RII): Relative measure

Transtheoretical Model (Stages of Change — Prochaska & DiClemente)

1. Precontemplation

Not thinking about change in next 6 months. Not yet aware of problem. Approach: raise awareness, non-judgmental information.

2. Contemplation

Thinking about change in next 6 months. Weighing pros & cons (decisional balance). Approach: tip the balance, explore ambivalence.

3. Preparation

Planning to act in next 30 days. Taking small steps. Approach: help develop a plan, set SMART goals.

4. Action

Actively changing behaviour <6 months. Needs support and reinforcement. Approach: positive reinforcement, relapse prevention.

5. Maintenance

Sustained change >6 months. Preventing relapse. Approach: coping strategies, identify triggers.

Relapse

Return to earlier stage. Normal part of process, not failure. Approach: resume cycle without judgment, learn from experience.

Motivational Interviewing (Brief)

Evidence-based, collaborative conversation style for strengthening motivation for change. Core spirit: PACE — Partnership, Acceptance, Compassion, Evocation.

OARS Techniques

Open questions — explore perspectives
Affirmations — acknowledge strengths
Reflective listening — demonstrate understanding
Summaries — collect and link information

Use 0–10 importance/confidence rulers: "How important is it for you to change? Why not lower?" Evokes change talk.

Community Health Needs Assessment & HIA

Community Needs Assessment (CNA) Steps

Define the community / population
Collect secondary data (mortality, morbidity, deprivation)
Conduct primary data collection (surveys, focus groups)
Identify health needs and priorities
Develop action plan with community involvement
Implement and evaluate

Health Impact Assessment (HIA)

Prospective analysis of likely health effects of a policy/project on a population. Steps: screening → scoping → appraisal → reporting → monitoring.

GCC NCD Statistics Summary ▼

Country	Diabetes Prevalence	Obesity (BMI≥30)	Hypertension	Under-5 Mortality
UAE	~17% adults	~31%	~30%	7/1,000 LB
Saudi Arabia	~18% adults	~35%	~35%	7/1,000 LB
Qatar	~17% adults	~33%	~32%	6/1,000 LB
Kuwait	~25% adults	~37%	~34%	8/1,000 LB
Bahrain	~18% adults	~29%	~28%	6/1,000 LB
Oman	~14% adults	~27%	~31%	10/1,000 LB

Sources: WHO EMRO, IDF Diabetes Atlas, national health surveys. Figures approximate and vary by survey year.

UAE Health Vision & Policy

UAE Vision 2021 / UAE Vision 2030

Reduce diabetes prevalence by 30% (target)
Increase healthy life expectancy to 75+ years
Universal health coverage for citizens
Mandatory health insurance in Abu Dhabi (since 2006) and Dubai (since 2014)
National Health Survey conducted regularly for baseline data

DHA (Dubai Health Authority)

Population Health Department: surveillance, NCD prevention, health promotion
Dubai Fitness Challenge (30×30 programme)
Weqaya programme (cardiovascular screening for nationals)
Dubai Cancer Registry
Watani programme for nationals

DOH / HAAD (Abu Dhabi)

HAAD became DOH (Dept of Health) Abu Dhabi in 2017
SEHA (Abu Dhabi Health Services Company) operates public hospitals
Mandatory health insurance for employees
Thiqa card for nationals — comprehensive coverage

Saudi Arabia Vision 2030 Health

Health transformation programme (HTP) — major reform agenda
Privatisation of healthcare facilities
Shift from hospital-centric to primary care-led model
NCD prevention targets: reduce obesity, tobacco, physical inactivity
VAT introduced 2018; tobacco tax increased to 100%
Expat fees & insurance requirements strengthened
SCFHS (Saudi Commission for Health Specialties) — regulates health professions
National Health Information Centre for data analytics
Vision 2030 KPI: increase life expectancy from 74 to 80 years

Saudi Arabia has the largest population in GCC (>35 million) and highest absolute NCD burden.

Qatar & Kuwait Health Systems

Qatar National Health Strategy (NHS)

MoPH (Ministry of Public Health) — regulator and planner
Hamad Medical Corporation (HMC) — main public hospital provider
Primary Health Care Corporation (PHCC) — national primary care network
NHSS 2018–2022 focus: population health, access, quality
Qatar Cancer Registry — established 2011
WHO CC for research on non-communicable disease prevention and control

Kuwait

MOH Kuwait — state provides free healthcare to citizens
Large expat population (70%+) creating dual health burden
High obesity rates — Kuwait ranks among highest globally
Kuwait Cancer Control Centre
Health reform ongoing — insurance system under development

Bahrain & Oman Health Systems

Bahrain

National Health Regulatory Authority (NHRA) — regulator
National health strategy aligned with Economic Vision 2030
Strong primary health care network (Health Centres)
National Cancer Registry operational
Electronic health record (Malaf) system
Waiver system for nationals accessing private care

Oman

Oman Vision 2040 includes health pillars
Ministry of Health Oman — integrated public health system
Strong PHC infrastructure — often cited as GCC model
Oman National Health Survey
Oman Diabetes/NCD prevention programme
Regional health system with governorate-level planning

Maternal & Child Health Indicators in GCC

Maternal Mortality Ratio (MMR)

Deaths per 100,000 live births. GCC MMR is very low compared to global average:

Global average: ~211/100k
UAE: ~3–5/100k
Qatar: ~8/100k
KSA: ~17/100k

Infant Mortality Rate (IMR)

Deaths under 1 year per 1,000 live births:

Global average: ~28/1k
UAE: ~5–7/1k
Qatar: ~6/1k
KSA: ~6–7/1k
Oman: ~9–10/1k

Under-5 Mortality Rate (U5MR)

Deaths under 5 per 1,000 live births. SDG target: ≤25/1k by 2030.

All GCC countries have already achieved this target. Congenital anomalies and preterm birth are leading causes in low-IMR settings.

High consanguinity in GCC → elevated genetic disease burden → congenital anomalies significant contributor to under-5 mortality.

GCC-Specific Epidemiology

Diabetes Epidemic

GCC has among the highest diabetes prevalence globally at 25–40% in some adult populations. Kuwait and Saudi Arabia consistently in top 10 globally. Drivers: rapid urbanisation, dietary transition (high refined carbohydrate, sugar-sweetened beverages), physical inactivity, genetic predisposition, high BMI.

Obesity Crisis

GCC obesity rates (BMI ≥30) range from 27–37%. Kuwait rates among world-highest. Physical inactivity exacerbated by hot climate, car-dependent culture, and limited outdoor space.

Consanguinity & Genetic Disease

First-cousin marriage rates: 25–60% in GCC countries. Result: elevated rates of autosomal recessive conditions: sickle cell disease, thalassaemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, congenital hearing loss. Premarital screening (PMS) programmes operational in UAE, Saudi Arabia, Qatar, Bahrain.

Road Traffic Accidents (RTAs)

Leading cause of death among young male Gulf nationals aged 15–44. Rates 2–3x higher than Western Europe. Factors: high vehicle speeds, mobile phone use, non-use of seatbelts, fatigue. UAE and Qatar have introduced camera systems and strict penalties.

Tobacco: Waterpipe / Hookah

Shisha (hookah) highly prevalent, especially among youth and in social settings. One shisha session = ~100× smoke inhalation of cigarette. Contains nicotine, carbon monoxide, heavy metals, carcinogens. Hookah cafes regulated inconsistently across GCC. Misperception that shisha is safer than cigarettes remains widespread.

Expat Health Disparities

Expats constitute 50–90% of GCC populations. Low-skilled workers have limited healthcare access, poor occupational health protections, heat stress exposure, overcrowded housing, limited mental health services. High-skilled expats generally have better access. Dual burden — wealthy expat employers vs. blue-collar workers.

Hajj & Umrah — Mass Gathering Medicine

Up to 2.5 million pilgrims in Makkah during Hajj — world's largest annual mass gathering. Unique public health challenges:

Infectious Disease Risks

Meningococcal disease: W135 strains — MenACWY vaccination mandatory since 2002
Respiratory infections: influenza, pneumonia, COVID-19, MERS-CoV (Saudi Arabia endemic)
MERS-CoV: Middle East Respiratory Syndrome coronavirus; camel reservoir; fatality ~35%
Cholera: historical risk; water/food safety critical
Polio vaccination required from endemic country pilgrims

Non-Communicable Risks

Heat-related illness: temperatures 40–50°C; heat exhaustion and heat stroke
Dehydration, rhabdomyolysis
Crush injuries (Mina stampede incidents)
Exacerbation of chronic conditions (cardiac events, respiratory failure)
Mental health crises

WHO EMRO Role

Enhanced surveillance during Hajj; Event-Based Surveillance (EBS); international health regulations coordination; daily sitreps to member states.

DHA / DOH / SCFHS Exam Prep — Epidemiology MCQ Focus Areas

Frequently Tested Calculations

Calculate incidence rate from line-listing data
Calculate attack rate in outbreak scenario
Distinguish prevalence from incidence in clinical scenario
Calculate RR and OR from 2×2 table
Calculate NNT from ARR
Identify appropriate study design for scenario
Sensitivity/specificity/PPV/NPV from 2×2 table
Herd immunity threshold from R₀

Study Design Scenarios

"Researchers followed 1,000 smokers and non-smokers for 10 years" = Cohort study
"200 lung cancer patients and 200 age-matched controls were interviewed about past smoking" = Case-control
"All adults in a town were surveyed on diet and diabetes status" = Cross-sectional
"Patients randomised to drug A or placebo" = RCT

Bias Recognition

"Cases better recall past exposure than controls" = Recall bias
"Patients hospitalised more likely to have two diseases" = Berkson bias
"Workers healthier than general population" = Healthy worker effect
"Variable related to exposure AND outcome" = Confounding

Wilson & Jungner — Common MCQs

Must have accepted treatment
Must have recognisable early stage
Cost must be reasonable
Test must be acceptable to population

Screening Test Interpretation

High Sensitivity + Low Prevalence = LOW PPV (many false positives)

SnNout: High Sensitivity, Negative result rules OUT

SpPin: High Specificity, Positive result rules IN

Outbreak Investigation — Exam Scenarios

Common MCQ Patterns

"First step in outbreak investigation" = Verify/confirm the diagnosis
"How to identify secondary transmission" = Secondary attack rate
"Single peak within one incubation period" = Point source outbreak
"Multiple peaks separated by incubation period" = Propagated outbreak
"Attack rate formula" = Cases / Exposed × 100
"What confirms common vehicle?" = Analytic study (cohort or case-control)
"When to implement control measures" = Do not wait for hypothesis testing; implement when suspected

Control measures should be implemented simultaneously with, not after, the investigation.

Key Formulas Revision Sheet

RR = [a/(a+b)] / [c/(c+d)]

OR = (a×d) / (b×c)

ARR = CER − EER | NNT = 1/ARR

Sensitivity = TP/(TP+FN) | Specificity = TN/(TN+FP)

PPV = TP/(TP+FP) | NPV = TN/(TN+FN)

LR+ = Sens/(1−Spec) | LR− = (1−Sens)/Spec

HIT = 1 − 1/R₀

SMR = (Observed/Expected) × 100

CFR = Deaths/Cases × 100

Attack Rate = Cases/At-risk × 100

Quick Mnemonics & Memory Aids

MPOWER

Monitor / Protect / Offer / Warn / Enforce / Raise

Ottawa Charter

Build healthy policy / Create environments / Strengthen community / Develop skills / Reorient services

Wilson & Jungner (Key 5)

Important condition | Early stage | Good test | Treatment available | Cost-justified

Stages of Change

Pre-contemplation → Contemplation → Preparation → Action → Maintenance

Outbreak Steps

Confirm → Define → Find → Describe → Hypothesise → Test → Control → Communicate → Report

PPE Hierarchy

Eliminate → Substitute → Engineer → Administrate → PPE