outbreak investigation - types of epidemics and investigating them

Investigation of outbreak/ epidemic

Presented by: Dr. Timiresh Kumar DasModerator: Dr. Neelam Roy

Associate Professor Dept. of Community MedicineVMMC & Safdarjung Hospital

OUTLINE OF PRESENTATION Definitions Determinants of disease outbreaks Types of epidemics Objectives of investigation of outbreak/

epidemic Steps of outbreak investigation Some examples References

DEFINITIONS Epidemic: [Greek: epi (upon) demos (the

people)] The occurrence in a community or region of cases of

an illness, specific health related behaviour, or other health related events clearly in excess of normal expectancy.1

A Dictionary of Epidemiology – 3rd ed; Last JM. 2000.

The “unusual” occurrence in a community or region of disease, specific health related behaviour, or other health related events clearly in excess of “expected occurrences”.2

Park’s Textbook of Preventive and Social Medicine – 21st ed; Park JE. 2010

The occurrence in a community or region of a group of illnesses of similar nature, clearly in excess of normal expectancy, and derived from a common or from a propagated source.3

Epidemiology – 4th ed; Gordis L. 2004

Outbreak: An epidemic limited to a localised increase in the

incidence of a disease, e.g., in a village, town, or closed institution. (= upsurge)1


A term used for a small, usually localised epidemic in the interest of minimising public alarm.2

Park’s Textbook of Preventive and Social Medicine – 21st ed; Park JE. 2010

An outbreak is the occurrence of illness, specific health related behaviour, or other event clearly in excess of normal expectancy in a community in a specified time period. An outbreak is limited or localised to a village, town, or closed institution.4

Checklist for CRRT for outbreak investigation, NICD 2008

DEFINITIONS

According to the Oxford Textbook of Public Health the criteria for judging that an outbreak has happened can be one of the following.5

The occurrence of a greater number of cases or events than normally occur in the same place when compared to the same duration in past years. E.g. Kaposi's sarcoma, New York - 30 in 1981; only 2-3

previous yrs. A cluster of cases of the same disease occurs which

can be linked to the same exposure. E.g. 3 athletes admitted with acute febrile illness after

triathlon in Springfield, Illinois. Triathlon related to illness. Leptospira.

A single case of disease that has never occurred before or might have a significant implication for public health policy and practice can be judged an outbreak which deserves to be investigated. E.g. - Avian flu (H5N1) Hong Kong in a 3-year boy in May

1997 alerted local auth. and scientists around the world to start a full-scale investigation.

DEFINITIONS

Endemic: The constant presence of a disease or infectious agent within a given geographic area or population group, without importation from outside; may also refer to the usual or expected frequency of the disease within such area or population group.


Pandemic: An epidemic usually affecting a large proportion of the population, occurring over a wide geographic area such as a section of a nation, the entire nation, or a continent or the world.


DEFINITIONS

DETERMINANTS OF DISEASE OUTBREAKS

When formerly isolated populations are exposed to disease. 19th century – measles in Faroe islands.

When susceptible population is introduced to an endemic area – streptococcal sore throat outbreaks when new recruits arrived at Great Lakes Naval Station, USA.

SUSCEPTIBLE IMMUNE

DISEASE OUTBREAK

NO

OUTBREAK

Herd Immunity: The immunity o f a group or community. The resistance of a group to invasion and spread of an infectious agent, based on the resistance to infection of a high proportion of the individuals members of the group.1

When a large proportion of the population is immune, the entire population is likely to be protected, not only those who are immune.

Degree depends on – Extent of random mixing of the populationAgent and transmission characteristics.Environmental factors.Number of susceptibles and immunes in the

population.


1958 1959 1960 19610

2

4

6

8

10

12

14

Expected number of cases if effect limited to vaccinesNumber of cases observed

REDUCED BY HERD IMMU-NITY

Effect of herd immunity: expected and observed numbers of paralytic poliomyelitis cases, US, 1958-1961

Incubation Period: Interval from receipt of infection to the time of onset of clinical illness.1

Important in case of isolating infected people to prevent transmission.

Isolation or quarantine should be greater than maximum incubation period.

Useful if disease may be introduced into new areas.


Quarantine: The restriction of activities of well persons or animals who have been exposed to a case of communicable disease during its period of communicability (i.e. contacts) to prevent disease transmission during incubation period if infection should occur.1

From quarante giorni (40 days). Plague (Black Death) Europe, 1374 – Venetian

Republic1377, Ragusa detained travellers in an isolated

area, initially for 30 days and, when it did not work, for 40 days


TYPES OF EPIDEMICS

Common-source epidemics Single source or point source epidemics Continuous or multiple exposure epidemics

Propagated epidemics Person to person Arthropod vector Animal reservoir

Slow (modern) epidemics

Point Source: A point source outbreak occurs when there is one single source that exists for a very short time and all cases have common exposure to it in that same particular period.

Ex: food poisoning

TYPES OF EPIDEMICS

Common source single exposureFirst case and the last case happen within

one incubation periodRapid rise in number of cases followed by

rapid decline

Example: Food poisoning due to spoiled food item in a

feast. Bhopal gas tragedy ( 198

TYPES OF EPIDEMICS

Common source multiple exposure: There is only one source, which provides continuous or intermittent exposure over a longer period

Example: Prostitute transmitting STD to her clients

Typhoid Mary

Water supply contamination due to leaky pipes. Continuous if leak is constant. Intermittent if leak occurs during pressure variations.

TYPES OF EPIDEMICS

Propagated epidemic: This kind of outbreak is caused by a transmission from one person to another person.

Example: SARS, H1N1 influenza

TYPES OF EPIDEMICS

OBJECTIVES OF INVESTIGATION OF EPIDEMIC To define the magnitude To determine the particular conditions and

factors responsible for the occurrence of the epidemic

To identify the cause, source of infection, and modes of transmission

To formulate prevention and control measures

PURPOSE OF INVESTIGATION OF EPIDEMIC To control the current outbreak.

Prevention of future outbreaks.

Describe new diseases and learn more about known

diseases.

Evaluation of the effectiveness of prevention programmes.

Evaluation of the effectiveness of the existing surveillance

system.

Training health professionals.

Responding to public, political, or legal concern .

WHO INVESTIGATES AN OUTBREAK ? The first person who comes across news

of an outbreak / The health worker/

ANM

PHC medical officer / the CHC in charge

The District health officer / District RRT

or DEIT/ State RRT

Specialized agencies like NCDC (NICD).

STEPS OF OUTBREAK INVESTIGATION1. Verification of the diagnosis2. Confirmation of existence of outbreak3. Defining population at risk – Map, Count4. Rapid search for cases and characteristics5. Data Analysis – Time, Place, Person6. Formulation of hypothesis7. Testing of hypothesis8. Evaluation of ecological factors9. Further investigations10.Reporting

WHAT TO DO FIRST Verify rumours Technical, Administrative and Logistics

arrangement Prepare Outbreak Management Kit

according to initial information Brief members of the investigating team

regardingRoles & responsibilitiesMethods of personal protection

Team composed of:1. Nodal officer (Epi/ PHS)2. Clinician3. Microbiologist

4. Health Assistant5. District/ Local

administration nominee6. Other personnel as

required

VERIFICATION OF DIAGNOSIS Verification of the diagnosis is usually made on

clinical and laboratory parameters. Ensure that the problem has been properly

diagnosed -- the outbreak really is what it has been reported to be

Review clinical findings and laboratory results for affected people

Visit or talk to several of the people who became ill

For outbreaks involving infectious or toxic chemical agents, be certain that the increase in diagnosed cases is not the result of a mistake in the laboratory.

CONFIRMATION OF EXISTENCE OF OUTBREAK Incidence rate is calculated by dividing the total

cases by the population at risk.

This rate is compared with the rate occurring in the same population, during the corresponding period of the previous years.

7 year average incidence vs. 2003 incidence of Dengue in Delhi

362

1861

600

101

1189

213 148

1510

0 0 0 0 0 14

1000000 2

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J F M A M J J A S O N D

months of reporting

no. o

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avg

EARLY WARNING OF OUTBREAKS• Clustering of cases or deaths• Increases in cases or deaths• Single case of disease of epidemic potential• Acute febrile illness of an unknown etiology• Two or more linked cases of disease with outbreak

potential(e.g., Measles, Cholera, Dengue, Japanese encephalitis or plague)

• Unusual isolate (Cholera O 139)• Unusual presentation• Environmental factors e.g. rainfall, climate• Shift in age distribution of cases • High vector density • Natural disasters

Sources of warningsRumour register

To be kept in standardized format in each institution

Community informantsPrivate and public sector

Media Important source of information, not to

neglectReview of routine data – surveillance

dataTriggers (There are triggers for each condition

under surveillance, Various trigger levels may lead to local or broader response)

Threshold for diseases under surveillance that trigger pre-determined actions at various levels

Based upon the number of cases in weekly report

Trigger levels depend on: Type of diseaseCase fatality (Death / case ratio)Number of evolving casesUsual trend in the region

Triggers in the context of IDSP


Trigger

Significance Levels of response

1 Suspected /limited outbreak

• Local response by health worker and medical officer

2 Outbreak • Local and district response by district surveillance officer and rapid response team

3 Confirmed outbreak • Local, district and state

4 Wide spread epidemic • State level response

5 Disaster response • Local, district, state and centre

Levels of response to different triggers

Examples: Trigger levels for Dengue

Trigger 1• Clustering of 2 similar case of probable Dengue fever in

a village• Single case of Dengue hemorrhagic fever

Trigger 2• More than 4 cases of Dengue fever in a village 1000

population.Triggers for syndromic surveillance

Fever• More than 2 similar case in the village (1000

Population) Jaundice

• More than two cases of jaundice in different houses irrespective of age in a village or 1000 population


Disease alerts/ outbreaks reported and responded to by states/ UTs through IDSP; 2nd week (ending 15th January, 2012)

Deciding to investigate a possible outbreak• Severity of illness• Number of cases• Source / mode of transmission• Availability of preventive & control measures• Availability of staff & resources • Public, political and legal concerns• Public health program considerations•Potential to affect others if the control measures are not taken• Research opportunity

Pseudo-outbreaks:Artifact in the numerator:

Increased awareness Reporting of prevalent cases as incident cases (e.g.;

hepatitis C, sleeping sickness) Laboratory error

Variation of the denominator: Rapidly changing population denominators Migrants or refugees

CONFIRMATION OF EXISTENCE OF OUTBREAK

DEFINING THE POPULATION AT RISK Obtain a map of the area Counting of the population

Helps to calculate the denominator for further calculation of attack rates.

Provides us with the possible number of people at risk.

Mapping helps us to know area: ecological and environmental factors.

Map : Detailed, Current map of the area.If not available – prepare Information: Natural landmarks, Roads, All

dwelling units, Sources of water, Other important features

Counting:Census by age and sexLay health workersHouse to house visits

DEFINING THE POPULATION AT RISK

SEARCH FOR CASES Includes: Framing a case definition, searching for cases

and doing a epidemiological survey.

A case definition is a standard set of criteria for deciding whether an individual should be classified as having the health condition of interest. Criteria

Clinical and/or biological criteria, Time Place Person

Case definition should be balanced, practical, reliable and applied without bias.

SEARCH FOR CASES: DefinitionExample - Measles: 3 definitions Fever and runny nose

Too sensitive Too many other illnesses produce same symptoms Call many illnesses “measles”

Fever and rash and Koplik’s spots and conjunctivitis Too specific Many cases of measles do not have all these signs Miss many real cases of measles

IDSP case definition: Fever of 3-7 days duration, with

generalized maculopapular rashes; with history of cough, coryza, conjunctivitis or Koplik’s spots.

Suspect -Fewer of the typical clinical features Probable- Typical clinical features of the disease

without laboratory confirmation. Confirmed- Typical clinical features with laboratory

verification.

SEARCH FOR CASES: Definition

Confirmed Case Probable Case Possible Case

LaboratoryVerification

ClinicalFeatures

+

++ ++ +

Example: E. coli O157 outbreak at Restaurant X on 31/3/2010Possible: diarrhea (3 loose stools per

day) and ate food purchased at restaurant X on 31/3

Probable: bloody diarrhea and ate food purchased at restaurant X during on 31/3

Confirmed: culture positive with “outbreak” PFGE pattern and ate food purchased from restaurant X on 31/3


Case Definition may need to be updated within an investigationBroad to specific

Infection with E. coli O157 vs. infection with the outbreak strain (defined by PFGE pattern)

Location of exposure SARS outbreak (travel within 10 d of onset):

• In February: China/HK/Hanoi/Singapore• In April: Toronto, Canada added• In May: Taiwan added

Dates of exposure can change SARS outbreak: to meet the case definition-dates

of exposure dependant on location of exposure


SEARCH FOR CASES: The search The first cases to be recognized are usually only a

small proportion of the total number

To identify other cases, use as many sources possible

Passive Surveillance - Relies on routine notifications by healthcare personnel

Active Surveillance - Involves regular outreach to potential reporters to stimulate reporting of specific conditions; investigators are sent to the afflicted area to collect more information Contact physician offices, hospitals, schools to

find persons with similar symptoms or illnesses Send out a letter, telephone or visit the facilities

to collect information Through media alerts asking people to get

checked

40Iceberg phenomenon

WHY TO SEARCH

SEARCH FOR CASES: Information The information is collected by “line

listing”.A line list is like a nominal roll of the cases being reported

to the various health care establishments (like dispensaries, general practitioners or admitted to the hospitals)

Constitutes and updates a database of casesDone by hand or by Excel.

SEARCH FOR CASES: Information

The survey team will go for “door to door” survey in the affected area and ask if any person had suffered with symptoms fitting into case definition (Rapid Household Survey)

If yes, their details were recorded on the epidemiological case - sheet and required samples are taken and dispatched to the hospital/ reference laboratory.Epidemiological case sheet = Case interview

formDetailed information from the case relevant

to the disease under study.


SEARCH FOR CASES: InformationInformation includes:• Name, Age, Sex, Occupation, Social class• Time of onset of disease, Signs & Symptoms• Personal contact at home, work, school• Travel history, attendance at large gatherings • History of previous exposure/injections,• Special events such as parties attended, foods

eaten, and exposure to common vehicles such as water, food and milk

Active door-to-door collection of information is by “ Rapid Household Survey”


DATA ANALYSIS: DESCRIPTIVE Characterizing an outbreak by time, place

and person is called descriptive epidemiology.

Descriptive epidemiology is important because:What is reliable and informative (e.g., similar

exposures)

What may not be as reliable (e.g., many missing responses to a particular question)

Provides a comprehensive description of an outbreak by showing its trend over time, its geographic extent (place) and the populations (people) affected by the disease

DESCRIPTIVE EPIDEMIOLOGY: Person Development of

proportional distribution of cases according to host characteristics (age, race, sex)

or

by exposures (occupation, leisure activities, use of medications, tobacco, drugs).

CountCount the cases in each age and sex groups

DivideObtain census denominators for each age and sex groups

Compare Estimate the incidence for each:

Age group Sex group

DESCRIPTIVE EPIDEMIOLOGY: Person

An attack rate is the proportion of a well-defined population that develops illness over a limited period of time, such as during an epidemic or outbreak

What are the age and gender specific attack rates?

What age and gender groups are at highest and lowest risk of illness?

In what other ways do the characteristics of the cases differ significantly from those of the general population?Purpose => Identification of sub-

group(s) at risk

Purpose => Identification of sub-

group(s) at risk



Characteristics Number of cases

Population

Attack rate per 100,000

Age group

0-4 50 255,755 19.6

5+ 51 1,795,383

2.8

Sex Male 48 1,032,938

4.6

Female 53 1,018,200

5.2

Total 101 2,051,138

4.9

Attack rate of measles by age and sex, Cuddalore, Tamil Nadu, India, 2004-2005


Population Cases of Botulism0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

ProtestantsCoptic ChristiansMuslims

Weber JT, Hibbs RG Jr, Darwish A, et al. A massive outbreak of type E botulism associated with traditional salted fish in Cairo. J Infect Dis 1993; 167: 451-454

BOTULISM OUTBREAK IN CAIRO, EGYPT - APRIL1993

DESCRIPTIVE EPIDEMIOLOGY: Time

What is the exact period of the outbreak?

What is the probable period of exposure?

Is the outbreak likely common source or propagated?


1. Count cases by time of onset

2. Eyeball distribution

to choose interval

3. Finalize

Drawing the epidemic curve based on time distribution of cases

Interpretation of epidemic curveShape – type of epidemicAn early case in the curve may represent source of the

epidemic Give information about the time course of an epidemic

and what the future course might beIn a point-source epidemic of a known disease with a

known incubation period, epidemic curve provides information to identify a likely period of exposure

Shape of epidemic curve illustrates type of epidemic.



Mean incubation period

Common source single exposure: Sharp increase followed by a rapid decline.

Continuous common source outbreak: An abrupt increase in the number of cases but, new cases

persist for a longer time with a plateau shape instead of a peak before decreasing.

• Intermittent common source: multiple peaks

Propagated source outbreak: Increase in the number of cases with progressive peaks

0

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Date

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DESCRIPTIVE EPIDEMIOLOGY: Place

The spatial relationships of cases are shown best on a spot map.

A spot map showing the location of cases can give an idea of the source of infection like maps show that the cases occurred in proximity to a body of water, a sewage treatment plant, or its outflow. DRAWING A ROUGH SPOT

MAP

DESCRIPTIVE EPIDEMIOLOGY: Place

Questions to be asked and answered:What is the most significant geographic

distribution of cases? Place of residence? Workplace?Do the attack rates vary by place?Relation to any landmark or possible

source?

FORMULATION OF HYPOTHESES Usually we generate hypotheses from the

beginning of the outbreak, however, at this point, the hypotheses are sharpened and

more accurately focused.

To consider what is known about the disease itself:A. What is the agent’s usual reservoir?B. How is it usually transmitted? C. What vehicles are commonly implicated? D. What are the known risk factors?

Talk to people who are ill: In-depth open interviews, Group discussions

Hypotheses should be proposed in a way that they can be tested.

FORMULATION OF HYPOTHESES

TESTING OF HYPOTHESES After a hypothesis is formulated, one should

be able to show that:all additional cases, lab data, and

epidemiologic evidence are consistent with the initial hypothesis

no other hypothesis fits the data as well

Observations that add weight to validity:

The greater the degree of exposure (or higher dosage of the pathogen), the higher the incidence of disease

Higher incidence of disease in the presence of one risk factor relative to other factors

Approaches:Comparison of hypothesis with known/ established

facts.Analytic epidemiology to test the hypothesis

First method is used when the evidence is so strong that hypothesis need not be testedExample - A 1991 investigation of an outbreak of

vitamin D intoxication in Massachusetts. All affected drank milk from local dairy. Hypothesis - dairy was source, milk vehicle of excess vit D. Visit to dairy, they quickly recognized that far more than the recommended dose of vitamin D was inadvertently being adding to the milk. No further analysis was necessary.

TESTING OF HYPOTHESES

Analytic epidemiology is used when cause is less clear. Cohort studiesCase control studies

What to use?


Case control

Cohort

Rare disease/ large community +++ -

Common disease/ small community

- +++

Complete population accessible +/- +++

Large amount of resources + ++

Limited resources +++ -


FOOD ATE and ILLN (%)

ATE and NOT ILLN (%)

ODDS RATIO

TOMATOES 14 (82) 30 (86) 0.83

CHICKEN 13 (71) 34 (94) 0.11

ALFAALFA SPROUTS 10 (67) 6 (17) 8.25

Example: Case control study for an outbreak of Acute Gastroenteritis following a dinner.

EVALUATION OF ECOLOGICAL FACTORS These are additional studies undertaken to

corroborate the findings of the epidemiological study.

Environmental studies

Microbiological studies

Entomological studies

Environmental studies often help explain why an outbreak occurred and may be very important in certain settings.Example: Site of contamination of irrigation

canal with cattle urine in an outbreak of Leptospirosis in southeastern Washington, August 1964.

EVALUATION OF ECOLOGICAL FACTORS

Pond connected to irrigation

canal And

Cattle around the site

Microbiological studies can clinch the relationship between suspected source and outbreak.Example: In the above outbreak of

Leptospirosis, culture of urine from the cattle, water of the canal and blood of affected children yielded the same strain of L. pomona. Also, the children who had recovered showed increased anti leptospiral antibodies.


Entomological studies help identify the vector responsible for the outbreak.May also give useful insight into the life

cycle of the pathogen and the mode of transmission


Example:Vector surveillance in Chikungunya affected villages of Latur and Beed districts of Maharashtra, 2006

FURTHER INVESTIGATIONS Additional epidemiologic studies

What questions remain unanswered about the disease?

What kind of study used in a particular setting would answer these questions?

When analytic studies do not confirm the hypotheses reconsider the original hypotheses look for new vehicles or modes of

transmission Additional investigations

Further lab studies

Refine hypothesis till confirmation

REPORTING Report provides a blueprint for action.

It also serves as a record of performance and a document for potential legal issues.

It serves as a reference if the health department encounters a similar situation in the future.

In public health literature serves the purpose of contributing to the knowledge base of epidemiology and public health

Daily interim reports and final report.

Contents of a Report:

1. Back ground

2. Historical data

3. Methodology of investigation

4. Analysis of data (clinical data, Epidemiological data, modes of transmission, Lab data, Interpretation of data)

5. Control measures

6. Evaluation

7. Preventive measures

REPORTING

Report to be submitted by investigating officer/ team to the next higher authority within one week of completion of investigations

CONTROL MEASURES Appropriate control measures

based on Epidemiological, Clinical, Environmental findings

To prevent further spread of disease

The elements of epidemic control include:

1.Controlling the source of the pathogen (if known) Remove or inactivate the pathogen

2.Interrupting the transmission. Sterilize environmental source of spread; vector control

3.Modifying the host response to exposure. Immunization; Prophylactic chemotherapy

Control measures should be implemented at the earliest.

DO NOT wait for laboratory confirmation to start control measures.

CONTROL MEASURES

WHAT NEXT Follow up of outbreak

Detect last caseDetect and treat late complicationsComplete documentation

Evaluation of outbreak management including investigations (by local authorities)Genesis of outbreakEarly or late detection of outbreakPreparedness for outbreakManagement of the outbreakControl measures taken and their impact

Documentation and sharing the lessons learntPost outbreak seminar.Feedback to local health authorities, RRTs and

other concerned.Developing case studies on selected

outbreaks for training purposes.

WHAT NEXT

Audience Medium Focus of the content

Communication objective

Epidemiologists, laboratory

•Report •Epidemiology •Documentation of the source

Public health managers

•Summary •Recommendations

•Action

Political leaders

•Briefing •Control measures

•Evidence that the situation is under control

Community •Press release, interview

•Health education

•Personal steps towards prevention

Scientific community

•Presentation, manuscript

•Science •Scientific progress

WHAT NEXT

POSSIBLE MATRIX FOR COMMUNICATION OF INVESTIGATION RESULTS AND FINDINGS

Example 1: Influenza in PTS

An outbreak of fever, URI & loose motion among the boarders of PTS, Jharoda kalan, Delhi was reported to the MS of SJH by CDMO of SW district of Delhi on 10.07.09 .

Cause for concern – Panic d/t novel H1N1 cases in Delhi

RRT composition – Epidemiologist, Physician, Microbiologist and other doctors. (11.07.09)

Case definition: A person with acute onset of fever with or without sore throat, diarrhea, headache, body ache starting from 2nd July 2009 onward.

Line listing, Epidemiological case sheet (with travel history), Lab analysis of samples for H1N1.

Descriptive:Time – Start = 2nd Jul, Peak = 7th Jul, Fall

afterwardsPlace – Start in Tent # 40, 25 & 8; then spread.

clustered around tent no 1,9,20, 22, 27, 36 &37.

Person – 61 cases. Mean age 22.2 yrs (20-49). Environmental: Crowded, ill ventilated tents.

Humid environment with low temperature. Lab: H1N1 negative. Influenza A +ve. Recommendations:

Reduce crowding, Improve ventilation Increase staffing in dispensary and Proper record

maintainancePrompt identification and reporting of changes in

disease frequency.

Example 1: Influenza in PTS

Example 2: Hepatitis RK Puram Outbreak of jaundice among the residents of Sector

8 of RK Puram, New Delhi was reported to the MS of SJH by CDMO of SW district of Delhi on 06.04.2011.

Initial report by DSO suggested sudden onset of jaundice.

RRT – Epidemiologist, Physician, Microbiologist and other personnel. To CGHS, dispensary on 06.04.2011

Case defn : A person with signs and symptoms of jaundice with or without elevated serum aminotransferase levels from 1st January 2011 onwards

Verification of outbreak by review of records of CGHS dispensary.

Rapid survey, Line listing, Spot map, Clinical examination, Epidemiological case sheet, Blood samples, Environmental study

Descriptive: Time – Rise from 15th Jan, Peak 1st week March,

Decline afterwards. Max cases in March (11/21)Place – Clustering around N block & adjacent to

Palam rdPerson – 15-30 yrs (50%), M > F (58.3/ 41.7)

Lab: 3/5 recent cases +ve for Anti HEV IgM. 2/6 water samples – Fecal contamination

Example 2: Hepatitis RK Puram

Environmental: Water & sewer lines running close, Intermittent water supply – Booster pumps, Latrine near water storage tank, Sewer lines not de-silted – overflowing, Damaged water lines. Absent residual chlorine.

Conclusion: Confirmed outbreak of jaundice. Lab results Acute Hepatitis E. Damaged water lines and contamination from sewer lines responsible.

Recommendations:Proper record maintenance in CGHS

dispensary(diagnosis, S/s)Monitoring and repairing of water linesSewer lines should not be close to water supply pipelineRegular de-silting and cleaning of sewer line.Proper chlorination of water supply.

Example 2: Hepatitis RK Puram

REFERENCES1. A Dictionary of Epidemiology – 3rd ed; Last

JM. 2000.2. Park’s Textbook of Preventive and Social

Medicine – 21st ed; Park JE. 2010.3. Epidemiology – 4th ed; Gordis L. 2004.4. Checklist for CRRT for outbreak

investigation, NICD 20085. Oxford Textbook of Public Health – 4th ed;

20026. Mausner & Bahn Epidemiology: An

Introductory Text – 2nd ed; Mausner JS, Kramer S. 1985.

REFERENCES7. R Bonita, R Beaglehole, T Kjellström.

Basic Epidemiology: WHO;2nd Edition.8. Outbreak Investigations Around The

World: Case Studies in Infectious Disease Field Epidemiology; Mark S Dworkin. 2010

9. Steps of outbreak investigation; Epidemiology in the classroom. Excite, CDC. From www.cdc.gov

10.Raut DK, Roy N, Nair D, Sharma R. Influenza A virus outbreak in Police Training School, Najafgarh, Delhi – 2009. Indian J Med Res; Dec 2010; 132: 731-732

http://www.cdc.gov/

THANK YOU

LARGE OUTBREAKS FROM AROUND THE WORLD – WHO, 1999

outbreak investigation - types of epidemics and investigating them

Education

region of disease

disease transmission

population group

population agent

health related events

single case of disease

disease orinfectious

case of communicable