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NHPC BPH practice questions

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Question 1Public Health Foundations, History, and Concepts

Which definition of public health best reflects the modern population-level mandate of the field?

  1. The clinical diagnosis and treatment of individual patients within hospitals
  2. The study of the biological mechanisms of a single disease in laboratory animals
  3. The organized efforts of society to prevent disease, prolong life, and promote health through collective action Correct answer.
  4. The administration of health insurance claims and hospital billing systems

Explanation

Public health is defined by organized, collective action aimed at preventing disease and promoting health across whole populations rather than treating individuals one at a time. This population focus and reliance on societal organization distinguish it from clinical medicine.

Question 2Public Health Foundations, History, and Concepts

The classic triad of core public health functions comprises assessment, policy development, and which third function?

  1. Accreditation
  2. Assurance Correct answer.
  3. Auditing
  4. Arbitration

Explanation

The Institute of Medicine framework identifies assessment, policy development, and assurance as the three core functions of public health. Assurance means ensuring that essential health services are available and competent.

Question 3Public Health Foundations, History, and Concepts

Which historical figure is most associated with identifying the Broad Street pump as the source of a cholera outbreak in London in 1854?

  1. Edward Jenner
  2. Louis Pasteur
  3. John Snow Correct answer.
  4. Robert Koch

Explanation

John Snow mapped cholera deaths in the 1854 London outbreak and linked them to the Broad Street water pump, a landmark in epidemiological reasoning. His investigation preceded the germ theory and relied on careful observation of exposure patterns.

Question 4Public Health Foundations, History, and Concepts

Primary prevention in public health is best illustrated by which activity?

  1. Immunization of children before exposure to a pathogen Correct answer.
  2. Screening mammography for early breast cancer detection
  3. Annual retinal examination in people with diagnosed diabetes
  4. Cardiac rehabilitation after a myocardial infarction

Explanation

Primary prevention acts before disease occurs, reducing incidence by removing or countering risk factors; immunization is the classic example. Secondary prevention detects existing but asymptomatic disease, and tertiary prevention limits disability after disease is established.

Question 5Public Health Foundations, History, and Concepts

A public health agency reports the number of new tuberculosis cases diagnosed in a district during one calendar year divided by the mid-year population. Which measure has been calculated?

  1. Case fatality rate
  2. Incidence rate Correct answer.
  3. Prevalence proportion
  4. Attack rate

Explanation

Incidence measures new cases arising in a population over a defined period, so new diagnoses in a year over the population at risk is an incidence rate. Prevalence would count all existing cases at a point or period, not only new ones.

Question 6Public Health Foundations, History, and Concepts

Which statement correctly describes the relationship between sensitivity and specificity of a screening test?

  1. Specificity is the probability of disease among people with a negative result
  2. Sensitivity is the probability of disease among people with a positive result
  3. Sensitivity is the probability of a positive result among people who truly have the disease Correct answer.
  4. Specificity is the probability of a negative result among people who truly have the disease

Explanation

Sensitivity is the proportion of truly diseased people whom the test correctly identifies as positive. Specificity, by contrast, is the proportion of truly non-diseased people correctly identified as negative.

Question 7Public Health Foundations, History, and Concepts

Which term describes the proportion of a population that must be immune to interrupt sustained transmission of an infectious agent?

  1. Basic reproduction number
  2. Herd immunity threshold Correct answer.
  3. Case fatality ratio
  4. Infectivity index

Explanation

The herd immunity threshold is the immune fraction needed to break chains of transmission in a population. It rises with the basic reproduction number, so more transmissible agents require higher coverage.

Question 8Public Health Foundations, History, and Concepts

The 1978 Declaration of Alma-Ata is historically significant in public health because it did which of the following?

  1. Launched the global smallpox eradication campaign
  2. Defined the Sustainable Development Goals for 2030
  3. Established the World Health Organization's first constitution
  4. Called for health for all through primary health care as a global goal Correct answer.

Explanation

The Alma-Ata Declaration articulated primary health care as the key to achieving health for all, shaping subsequent global health policy. It was issued at an international conference convened by WHO and UNICEF in 1978.

Question 9Public Health Foundations, History, and Concepts

Which pair correctly matches a public health achievement with its principal historical driver?

  1. Smallpox eradication and a global vaccination campaign led by WHO Correct answer.
  2. Malaria elimination and widespread use of bed nets alone
  3. Cholera control and routine antibiotic prophylaxis
  4. Polio eradication and mandatory quarantine of all travellers

Explanation

Smallpox was declared eradicated in 1980 after a sustained global vaccination and surveillance campaign coordinated by WHO. Eradication relied on case finding, ring vaccination, and surveillance rather than a single tool.

Question 10Public Health Foundations, History, and Concepts

An outbreak of gastroenteritis occurs after a community meal. Investigators compare food exposures between those who became ill and those who did not. Which study design is most appropriate at this stage?

  1. Randomized controlled trial
  2. Ecological correlation study
  3. Prospective double-blind trial
  4. Retrospective cohort study Correct answer.

Explanation

When a defined group shares an exposure and outcomes are already known, a retrospective cohort design computes attack rates by exposure and identifies the implicated item. Randomized trials are neither ethical nor feasible during an acute outbreak.

Question 11Public Health Foundations, History, and Concepts

Which of the following best describes the epidemiological transition?

  1. The replacement of clinical care with community health workers
  2. A shift from infectious disease dominance to chronic noncommunicable disease dominance as populations develop Correct answer.
  3. The migration of health workers from rural to urban facilities
  4. A change in the dominant mode of disease transmission from vector-borne to airborne

Explanation

The epidemiological transition describes changing disease patterns, with communicable diseases and malnutrition giving way to chronic noncommunicable conditions as mortality declines. It is accompanied by demographic ageing and shifts in life expectancy.

Question 12Public Health Foundations, History, and Concepts

Which determinant of health is classified as a structural or upstream factor rather than a downstream behavioural one?

  1. Dietary salt intake
  2. Physical activity level
  3. Tobacco smoking status
  4. Household income and housing quality Correct answer.

Explanation

Upstream determinants such as income, housing, and education shape the distribution of risk factors across populations. Behaviours like diet, smoking, and activity are downstream and are themselves influenced by these structural conditions.

Question 13Public Health Foundations, History, and Concepts

A district health team maps households, identifies unimmunized children, and arranges outreach sessions to reach them. Which core public health function does this activity most directly illustrate?

  1. Assurance Correct answer.
  2. Policy development
  3. Regulation
  4. Assessment

Explanation

Assurance means guaranteeing that essential services, including immunization, reach the population, often through outreach and linkage to care. Assessment would involve measuring coverage, and policy development would involve setting the immunization policy itself.

Question 14Public Health Foundations, History, and Concepts

Which measure of disease burden expresses years of life lost to premature death plus years lived with disability?

  1. Quality-adjusted life years
  2. Standardized mortality ratio
  3. Life expectancy at birth
  4. Disability-adjusted life years Correct answer.

Explanation

Disability-adjusted life years combine years of life lost from premature mortality with years lived with disability, providing a single metric of overall burden. Quality-adjusted life years instead weight survival time by health-related quality of life for economic evaluation.

Question 15Public Health Foundations, History, and Concepts

In the history of public health, Edwin Chadwick's 1842 report on sanitary conditions is most closely associated with which idea?

  1. That vaccination alone can eliminate all infectious disease
  2. That hospitals are the primary site of preventive care
  3. That environmental sanitation and living conditions drive population health Correct answer.
  4. That disease is caused by miasma produced only by human contact

Explanation

Chadwick's report linked poor sanitation, crowding, and drainage to excess mortality and helped drive sanitary reform in Britain. It reflected the sanitary idea that environmental conditions shape population health, even before germ theory.

Question 16Public Health Foundations, History, and Concepts

Which statement about the difference between health equity and health equality is correct?

  1. Equity and equality are interchangeable terms in public health policy
  2. Equity requires allocating resources according to need so that avoidable differences are reduced Correct answer.
  3. Equality requires that everyone receive identical health outcomes regardless of need
  4. Equity means providing the same service to everyone irrespective of circumstances

Explanation

Health equity concerns fairness, distributing resources according to need to reduce avoidable and unjust differences. Equality means treating everyone the same, which can preserve disadvantage when needs differ.

Question 17Public Health Foundations, History, and Concepts

The Ottawa Charter for Health Promotion identified five action areas. Which of the following is one of them?

  1. Standardizing hospital accreditation
  2. Eradicating all communicable diseases
  3. Mandatory disease notification
  4. Building healthy public policy Correct answer.

Explanation

The 1986 Ottawa Charter set out action areas including healthy public policy, supportive environments, community action, personal skills, and reorientation of health services. These emphasize the conditions and settings that shape health rather than single-disease targets.

Question 18Public Health Foundations, History, and Concepts

A programme reports that the number of deaths from a disease fell while the case fatality rate rose. Which explanation is most consistent with these findings?

  1. Fewer people developed the disease, and those who did were more likely to die Correct answer.
  2. The population grew rapidly while treatment improved
  3. Diagnosis became more sensitive and detected milder cases
  4. The disease became less severe but more common

Explanation

Total deaths depend on both incidence and case fatality. A fall in deaths alongside a rising case fatality rate is consistent with a large decline in new cases outweighing the higher lethality among those affected.

Question 19Public Health Foundations, History, and Concepts

Which statement about the demographic transition is most accurate?

  1. Mortality typically declines before fertility, producing a period of rapid population growth Correct answer.
  2. Fertility typically falls before mortality, producing immediate population ageing
  3. Both mortality and fertility rise together throughout the transition
  4. Population size remains constant across all stages of the transition

Explanation

In the classic demographic transition, death rates fall first, followed later by declining birth rates, so the intervening gap produces rapid population growth. Population ageing follows as fertility and mortality both fall.

Question 20Public Health Foundations, History, and Concepts

Which activity is an example of secondary prevention at the population level?

  1. Organized cervical cancer screening for eligible women Correct answer.
  2. Rehabilitation services after a stroke
  3. Nutrition education for schoolchildren
  4. Legislation requiring seat-belt use in vehicles

Explanation

Secondary prevention detects and treats asymptomatic disease early to improve outcomes, and organized screening programmes are a population-level example. Seat-belt laws and nutrition education are primary prevention, while rehabilitation is tertiary.

Question 21Epidemiology and Disease Surveillance

In disease surveillance terminology, what does the 'epidemic curve' primarily display?

  1. The geographic spread of a disease across districts
  2. The proportion of the population that is immune
  3. The distribution of cases over time during an outbreak Correct answer.
  4. The cumulative cost of treating reported cases

Explanation

An epidemic curve is a histogram that plots the number of new cases against the date or time of onset. Its shape helps investigators infer the mode of transmission and estimate the likely exposure period. Geographic and cost data belong to other surveillance outputs.

Question 22Epidemiology and Disease Surveillance

A public health unit wants to detect unusual increases in a specific notifiable disease as early as possible. Which surveillance approach is designed primarily for this purpose?

  1. Syndromic surveillance Correct answer.
  2. Seroprevalence survey
  3. Indicator-based surveillance
  4. Sentinel surveillance

Explanation

Syndromic surveillance monitors pre-diagnostic indicators such as symptom patterns or pharmacy sales to flag potential outbreaks early. Indicator-based systems rely on confirmed diagnoses reported through routine channels, which are slower. Sentinel sites and serosurveys serve different monitoring goals.

Question 23Epidemiology and Disease Surveillance

Which measure of disease frequency best estimates the probability that a susceptible person will develop a disease during a defined period?

  1. Mortality rate
  2. Point prevalence
  3. Incidence proportion Correct answer.
  4. Case fatality ratio

Explanation

Incidence proportion (cumulative incidence) is the number of new cases divided by the population at risk over a period, approximating individual risk. Prevalence counts existing cases at a point in time and does not measure risk directly. Case fatality and mortality describe outcomes among cases or the whole population.

Question 24Epidemiology and Disease Surveillance

In an outbreak investigation, the primary purpose of a line list is to:

  1. Record each case with key variables for analysis and follow-up Correct answer.
  2. Determine the national vaccination schedule
  3. Define the laboratory testing protocol for specimens
  4. Calculate the total budget required for the response

Explanation

A line list is a tabular record with one row per case and columns for variables such as age, sex, onset date, location, and exposure. It supports descriptive analysis, hypothesis generation, and monitoring. Budgeting and protocol design are separate management activities.

Question 25Epidemiology and Disease Surveillance

A district reports 40 new cases of a disease over one year among a population of 20,000. What is the incidence rate per 1,000 person-years (assuming the whole population was followed for the year)?

  1. 0.2 per 1,000
  2. 2 per 1,000 Correct answer.
  3. 20 per 1,000
  4. 200 per 1,000

Explanation

Incidence per 1,000 equals (new cases / population) multiplied by 1,000, giving (40/20,000) x 1,000 = 2 per 1,000. This standardizes the count to a convenient base. The other values reflect decimal or scaling errors.

Question 26Epidemiology and Disease Surveillance

Which surveillance system characteristic is most directly improved by requiring laboratories to report confirmed cases electronically in near real time?

  1. Timeliness Correct answer.
  2. Representativeness of the population
  3. Specificity of case definitions
  4. Simplicity of the reporting form

Explanation

Near real-time electronic laboratory reporting shortens the interval between case occurrence and public health awareness, which is the definition of timeliness. Specificity, representativeness, and form simplicity are separate attributes of a surveillance system.

Question 27Epidemiology and Disease Surveillance

The case fatality ratio of a disease is calculated as:

  1. Deaths from the disease divided by diagnosed cases of the disease Correct answer.
  2. Deaths from all causes divided by total deaths
  3. New cases divided by the total population
  4. Deaths from the disease divided by the population at risk

Explanation

The case fatality ratio expresses the proportion of diagnosed cases who die from the disease, using deaths in the numerator and cases in the denominator. Using the whole population in the denominator would produce a mortality rate instead. All-cause fractions have no role here.

Question 28Epidemiology and Disease Surveillance

Which of the following best defines 'active surveillance'?

  1. Publishing aggregate annual statistics
  2. Analyzing death certificates retrospectively
  3. Public health staff proactively contacting facilities to collect case data Correct answer.
  4. Waiting for health facilities to submit routine reports

Explanation

Active surveillance involves public health workers actively seeking case information from facilities or the community rather than passively awaiting reports. Passive surveillance relies on routine submission by reporting sites. Retrospective and aggregate analyses are separate activities.

Question 29Epidemiology and Disease Surveillance

An outbreak of gastroenteritis occurs after a wedding dinner. Investigators compare foods eaten by ill and non-ill attendees. Which study design is most appropriate for identifying the likely vehicle?

  1. Retrospective cohort study Correct answer.
  2. Ecological correlation study
  3. Randomized controlled trial
  4. Cross-sectional serosurvey

Explanation

When a defined group is exposed at a known event, a retrospective cohort design can compute attack rates by exposure and identify the vehicle. A randomized trial is neither ethical nor feasible during an outbreak. Serosurveys and ecological designs cannot link specific foods to illness at the individual level.

Question 30Epidemiology and Disease Surveillance

Which term describes the constant presence of a disease at a predictable baseline level within a defined geographic area?

  1. Endemic Correct answer.
  2. Sporadic
  3. Pandemic
  4. Epidemic

Explanation

Endemic refers to the usual, predictable occurrence of a disease in a population within a geographic area. An epidemic is an increase above the expected level, a pandemic spreads across continents, and sporadic cases occur irregularly without a stable pattern.

Question 31Epidemiology and Disease Surveillance

A surveillance system reports many false positives because its case definition is very broad. Which attribute is most affected?

  1. Timeliness
  2. Stability
  3. Positive predictive value Correct answer.
  4. Sensitivity

Explanation

A broad case definition raises sensitivity but lowers the proportion of reported cases that are truly cases, reducing positive predictive value. Timeliness and stability concern speed and reliability of the system, not the accuracy of case classification.

Question 32Epidemiology and Disease Surveillance

Which denominator is used when calculating an age-specific mortality rate?

  1. Mid-year population in that age group Correct answer.
  2. Number of hospital admissions in that age group
  3. Total confirmed cases in that age group
  4. Total deaths in all age groups

Explanation

An age-specific mortality rate divides deaths in a given age group by the mid-year population of that same age group, usually multiplied by a constant. This restricts both numerator and denominator to the age stratum. The other denominators describe different measures.

Question 33Epidemiology and Disease Surveillance

During an outbreak, investigators plot cases by date of symptom onset and observe a single sharp peak with all cases occurring within one incubation period. This pattern most suggests:

  1. A continuous common-source exposure
  2. A vector-borne seasonal pattern
  3. A point-source exposure Correct answer.
  4. A propagated person-to-person spread

Explanation

A single sharp peak confined to roughly one incubation period indicates a brief, simultaneous exposure, characteristic of a point source. Continuous common-source exposure produces a plateau, while propagated spread yields successive peaks one incubation period apart.

Question 34Epidemiology and Disease Surveillance

Which of the following is an example of a notifiable disease surveillance requirement?

  1. Hospitals must report staff attendance
  2. Pharmacies must publish their prices
  3. Patients must consent to all laboratory testing
  4. Health facilities must report specified diagnoses to public health authorities Correct answer.

Explanation

Notifiable disease surveillance legally requires clinicians and laboratories to report listed conditions to public health authorities so that control measures can be initiated. Consent for testing, price publication, and staff attendance are unrelated administrative matters.

Question 35Epidemiology and Disease Surveillance

A screening test has high sensitivity but low specificity. What is the main consequence in a surveillance context?

  1. The test cannot be repeated
  2. The test will be too slow to administer
  3. Many people without disease will be flagged Correct answer.
  4. Many true cases will be missed

Explanation

High sensitivity means few true cases are missed, but low specificity means many non-cases test positive, generating false alarms. In surveillance this can overwhelm investigators with false signals. Speed and repeatability are separate operational properties.

Question 36Epidemiology and Disease Surveillance

Which measure describes the number of existing cases of a disease in a population at a specific point in time?

  1. Relative risk
  2. Incidence rate
  3. Point prevalence Correct answer.
  4. Attack rate

Explanation

Point prevalence counts all existing cases, both new and old, at a single moment divided by the population. Incidence and attack rates measure new cases, and relative risk compares risk between exposed and unexposed groups.

Question 37Epidemiology and Disease Surveillance

An investigator wants to compare the risk of disease between people exposed and not exposed to a suspected risk factor. Which measure is most appropriate?

  1. Relative risk from a cohort study Correct answer.
  2. Odds ratio from a case-control study
  3. Prevalence ratio from a single survey
  4. Standardized mortality ratio

Explanation

When incidence can be measured in both exposed and unexposed groups, a cohort study yields relative risk, the ratio of attack rates. Odds ratios are used when incidence cannot be directly estimated, as in case-control designs. Prevalence ratios and standardized mortality ratios answer different questions.

Question 38Epidemiology and Disease Surveillance

Which step comes first in a standard outbreak investigation sequence?

  1. Writing the final report
  2. Verifying the diagnosis and confirming the existence of an outbreak Correct answer.
  3. Implementing control measures
  4. Performing a case-control analysis

Explanation

Before investigating, investigators must confirm that the diagnoses are correct and that case numbers exceed the expected baseline. Control measures may begin early but the formal sequence starts with verification. Analysis and reporting follow later.

Question 39Epidemiology and Disease Surveillance

A country reports a sharp rise in measles cases among children aged 1-4 years. Which surveillance data source would best confirm whether this reflects true increased transmission rather than improved reporting?

  1. Laboratory confirmation rates over the same period Correct answer.
  2. Newspaper coverage of the disease
  3. Pharmacy sales of antipyretics
  4. Hospital parking records

Explanation

Comparing laboratory confirmation rates over time helps distinguish a genuine increase in transmission from changes in reporting practices. If confirmation rates rise alongside case counts, true transmission is more likely. The other sources are indirect and cannot confirm diagnosis.

Question 40Epidemiology and Disease Surveillance

Which term refers to the resistance of a population to invasion and spread of an infectious agent because a high proportion of individuals are immune?

  1. Herd immunity Correct answer.
  2. Case isolation
  3. Quarantine
  4. Passive immunity

Explanation

Herd immunity is the indirect protection that arises when a sufficient proportion of a population is immune, limiting transmission to susceptible individuals. Passive immunity is antibody transfer to an individual, while isolation and quarantine are control measures applied to individuals.

Question 41Epidemiology and Disease Surveillance

A surveillance officer calculates a standardized mortality ratio of 150 for a district. How should this be interpreted?

  1. Observed deaths are 150% higher than expected
  2. Observed deaths equal the expected number
  3. Observed deaths are 50% higher than expected for the standard population Correct answer.
  4. Observed deaths are 50% lower than expected

Explanation

A standardized mortality ratio is observed deaths divided by expected deaths, multiplied by 100. A value of 150 means observed deaths are 1.5 times, or 50% higher than, the expected number. Values below 100 indicate fewer deaths than expected.

Question 42Epidemiology and Disease Surveillance

Which feature most distinguishes a case-control study from a cohort study in outbreak settings?

  1. Random assignment is used to allocate exposure
  2. Cases are selected by disease status and compared on past exposures Correct answer.
  3. Participants are followed forward in time from exposure
  4. Incidence is directly calculated in both groups

Explanation

Case-control studies begin with people who have the disease and compare their past exposures with those of controls. Cohort studies start with exposure groups and follow them forward to measure incidence. Neither observational design uses random assignment.

Question 43Epidemiology and Disease Surveillance

Which action best illustrates the use of surveillance data for public health action rather than mere data collection?

  1. Entering case data into a register
  2. Printing annual statistics for the archive
  3. Triggering a vaccination campaign after detecting a measles cluster Correct answer.
  4. Archiving case reports without review

Explanation

Surveillance achieves its purpose when data inform timely interventions such as immunization campaigns. Merely archiving, entering, or printing data without response describes data handling rather than action. The measles cluster example links detection directly to control.

Question 44Epidemiology and Disease Surveillance

In a cohort of 500 exposed and 500 unexposed persons, 50 exposed and 10 unexposed develop disease. What is the relative risk?

  1. 10.0
  2. 0.5
  3. 5.0 Correct answer.
  4. 0.2

Explanation

The attack rate in the exposed is 50/500 = 0.10, and in the unexposed is 10/500 = 0.02. Relative risk is 0.10 / 0.02 = 5.0, indicating five times the risk among the exposed. The other values reflect incorrect ratios or inversion.

Question 45Epidemiology and Disease Surveillance

Which statement accurately describes the relationship between prevalence and incidence?

  1. Prevalence depends only on the number of new cases
  2. Prevalence depends on both incidence and the duration of disease Correct answer.
  3. Prevalence and incidence are always equal
  4. Incidence depends on the duration of disease

Explanation

Prevalence is approximately the product of incidence and average disease duration, so longer-lasting diseases accumulate more prevalent cases. Incidence reflects only new cases over time. They are equal only under very specific, unusual conditions.

Question 46Epidemiology and Disease Surveillance

A district health office wants to detect a sudden increase in dengue cases as early as possible. Which surveillance approach is most suitable for this purpose?

  1. Syndromic surveillance using emergency department chief complaints Correct answer.
  2. Sentinel surveillance at selected hospitals
  3. Active case finding through house-to-house surveys
  4. Retrospective analysis of hospital discharge records

Explanation

Syndromic surveillance monitors pre-diagnostic data such as chief complaints or absenteeism to detect outbreaks earlier than traditional case-based reporting. Sentinel surveillance is limited to selected sites and may not provide timely population-wide signals. Active case finding and retrospective record review are labor-intensive and not designed for early detection.

Question 47Epidemiology and Disease Surveillance

In a community of 10,000 people, 500 have diabetes at the start of the year. During the year, 100 new cases are diagnosed. What is the incidence rate of diabetes for that year?

  1. 5 per 100 person-years
  2. 1 per 100 person-years Correct answer.
  3. 10 per 100 person-years
  4. 50 per 100 person-years

Explanation

Incidence rate = new cases / population at risk at start of follow-up. The population at risk is 10,000 − 500 = 9,500, so 100 / 9,500 ≈ 0.0105, or about 1 per 100 person-years. Using the total population (10,000) would give 1 per 100 as well, but the correct denominator excludes existing cases.

Question 48Epidemiology and Disease Surveillance

Which measure is most appropriate for comparing the burden of a chronic disease between two populations with very different age structures?

  1. Case fatality ratio
  2. Crude mortality rate
  3. Age-specific mortality rate
  4. Age-standardized mortality rate Correct answer.

Explanation

Age-standardized mortality rates adjust for differences in age distribution, allowing valid comparison of disease burden between populations. Crude rates are influenced by age structure, and age-specific rates apply to individual age groups rather than the whole population. The case fatality ratio measures deaths among cases, not population burden.

Question 49Epidemiology and Disease Surveillance

Which statement best describes the purpose of a notifiable disease list in public health surveillance?

  1. It provides a list of diseases for which treatment is free of charge.
  2. It requires health care providers and laboratories to report specified diagnoses to public health authorities. Correct answer.
  3. It mandates isolation of all patients with the listed diseases.
  4. It defines the case definitions used in outbreak investigations.

Explanation

A notifiable disease list legally obliges clinicians and laboratories to report cases of specified diseases to public health authorities, enabling monitoring and response. It does not automatically mandate isolation, provide free treatment, or establish case definitions; those are separate functions.

Question 50Epidemiology and Disease Surveillance

During an outbreak investigation, investigators calculate an attack rate of 60% among people who ate potato salad and 15% among those who did not. Which interpretation is most appropriate?

  1. Potato salad is protective because the attack rate is higher in those who ate it.
  2. Potato salad is the likely vehicle because the attack rate is lower in exposed persons.
  3. Potato salad is unrelated to illness because both groups had cases.
  4. Potato salad is the likely vehicle because the attack rate is substantially higher in exposed persons. Correct answer.

Explanation

A much higher attack rate among those who ate the food suggests it is the likely vehicle of infection. The ratio of attack rates (60%/15% = 4) indicates a strong association. A protective food would show a lower attack rate in exposed persons, and an unrelated food would show similar attack rates in both groups.