I is for Investigation

Outbreak Investigation Methods from Mystery to Mastery

Session VI

Writing an Outbreak Report

Session Overview

• Outbreak report function and structure

• Case studies– Mycobacterium skin infection outbreak in New

York in 2012– Multistate outbreak of listeriosis in 2011

Learning Objectives

• Explain the role of outbreak investigation reports

• Describe different types of outbreak reports

• List elements to include in outbreak investigation reports

Basic Steps of an Outbreak Investigation

• Verify the diagnosis and confirm the outbreak

• Define a case and conduct case finding

• Tabulate and orient data: time, place, person

• Take immediate control measures

• Formulate and test hypothesis

• Plan and execute studies

• Implement and evaluate control measures

• Communicate findings

Outbreak Report Function and Structure

Why Communicate the Findings?

• Serves as a document for action

• Gives insight about pathogen or transmission mechanism

• Documents the magnitude of health problems and justifies activities

• Serves as a performance measure for Public Health Preparedness capabilities

• Is a basis for research or evaluation

Communicating Findings

• Prevent future outbreaks

• Assist in investigation and control of similar incidents

• Provide a document for potential legal issues

Why are Outbreak Reports Crucial to Public Health?

Example: Foodborne outbreakInvasive listeriosis in Louisiana, Jan-June 2010

• First outbreak to implicate hog head cheese• Voluntary recall by producer• Publication served to

– Inform public health practitioners about new transmission vehicle

– Emphasize food safety requirements– Alert high risk populations

Why are Outbreak Reports Crucial to Public Health?

Example: Respiratory disease outbreak

•1996 Legionnaire’s Disease (LD) outbreak associated with a whirlpool spa display

– Exposure from walking by or being near spa•1999 LD outbreak at a flower show in the Netherlands

– Source: whirlpool spas on display– Lawsuit raised against Dutch government – Failure to act on available knowledge (1996

MMWR)

Some Reports are a Part of History

John Snow

Image Source: www.circleofblue.org 

Some Reports are a Part of History

Morbidity and Mortality Weekly Report (CDC), June 5, 1981

When is the Report Written?

• When the investigation is ‘complete’

• When the investigation is ‘ongoing’– Preliminary results impact public health /

medical practice– High profile or high interest– Long investigation– Often include disclaimer

Who Writes the Report?

• The outbreak / field epidemiology team– Visiting EIS officer– Epidemiologist, environmental health,

laboratorians, clinicians– Participating state or federal agencies

All participating agencies must

approve the report.

Types of Reports

• Complaint form• Internal report

– Record that outbreak occurred and investigation was conducted

• State publications – Newsletter, bulletin, website, press release or alert

• National bulletin – MMWR http://www.cdc.gov/mmwr/

• Peer-Reviewed Journals– Epidemiology and Infection, Emerging Infectious

Diseases, Journal of Hospital Infection

http://www.ncbi.nlm.nih.gov/pubmed

Peer-Reviewed Articles

Research Outbreak Updates

• MMWR: http://www.cdc.gov/mmwr/

• FoodNet: www.cdc.gov/foodnet/

• Bulletin of the World Health Organization

www.who.int/bulletin/

• ProMED-mail listserv www.promedmail.org

Basic Report Structure

• Context / background• Initiation of investigation• Investigation methods• Findings / results• Discussions and/or conclusions• Recommendations• Acknowledgements

+Supporting Documentation

Length of Report

• Bulletin article– 1-2 pages (500-1000 words)

• Internal report– 2-3 pages

• Peer-reviewed manuscript– 4-8 pages

Context and Background

• Description of the problem– Suspected or known etiology– Signs, symptoms, diagnoses– Time of occurrence

• Population affected

• Location / and geographical areas involved

Initiation of Investigation

• How notification was received

• Date and time notification was received by the agency

• Date and time investigation was initiated

Methods

• Initial activity / verification– Laboratory results, case finding efforts

• Data collection and analysis methods– Case definition and case identification– Epidemiologic study design– Environmental or clinical sample collection– Review of reports

• Exposure assessment and classification• Tools used

– Questionnaires, epidemic curves, attack rates

Epidemiological Results

• Questionnaire / interview response rate• Cases

– Number– Descriptive and clinical data – Geographic distribution of cases– Epidemic curve

• Attack rates by age, sex, exposure• Risk factor analysis, including ORs / RRs if

applicable

Laboratory, Clinical, and Environmental Results

• Laboratory results– Findings from clinical or environmental testing– Genotyping, DNA fingerprinting, culture

results

• Environmental– Results of any risk assessments– Results of any traceback investigation

Discussion and/or Conclusions

• Discuss main hypotheses and public health impact of findings

• Note problems or limitations that could impact results

• Present conclusions about the cause of the outbreak

Recommendations

• Uses– To control or mitigate this outbreak– To prevent future outbreaks– To improve management of future outbreaks

• Basis– Investigation obstacles and shortcomings– Outbreak causes

Acknowledgements

• Key investigators

• Report authors

• Both names and titles

Supporting Documentation

Also include the following:Graphs and tables

Inspection reports

Blank samples of surveys

Letters to management

Menus

Copies of posted notices

Testing results

Press releases

Maps

Case Studies

Case Study 1

Outbreak of Mycobacterium chelonae Infection Associated with Tattoo

Ink

Kennedy, Bedard, Younge, et al. N Engl J Med 2012; 367:1020-1024. September 13, 2012.

Tattoo Ink OutbreakContext and Background

• Pathogen– Not a common cause of skin infections

• Setting– Previous case reports and outbreaks– General description of current outbreak

Initiation of Investigation• Dermatologist reported case to health

department

Stain showing Acid-Fast Bacilli Kennedy et al. NEJM 2012; 367:1020-1024

Tattoo Ink OutbreakEpidemiologic Methods

• Interviews and site visit– Index patient– Tattoo artist and studio

• Additional case finding– Laboratories and tattoo parlors– Assessment and treatment

Tattoo Ink OutbreakLaboratory Methods

• Laboratories used

• Samples tested

• Tests performed

Typical Rash Associated with Mycobacterium chelonae InfectionKennedy et al. NEJM 2012; 367:1020-1024

Tattoo Ink OutbreakEpidemiologic Results

• Ink purchased in April, additional supply ordered later

• 19 cases (15 confirmed, 4 probable, 1 suspected)– 13 men, 6 women– Age range 18 – 48 years

• Attack rate among parlor patrons– 0% May-August 2011– 65% in November 2011

Tattoo Ink OutbreakLaboratory Results

• Biopsy from 17 of 19 case patients– Microscopic evidence in all samples– M. chelonae isolated from 14 of 17 samples

• CDC confirmed same M. chelonae genetic pattern in 11 clinical samples and 1 unopened bottle of ink

• No M. chelonae found in environmental samples from tattoo parlor

Tattoo Ink OutbreakDiscussion and Conclusions

• Conclusion:Ink, not tattoo parlor, was source of infection

• Discussion–Brief review of mycobacterial contamination during tattoo procedures–Limitations–Implication of possible under-reporting of cutaneous mycobacterium infections

Tattoo Ink OutbreakRecommendations

• Educate tattoo artists and patrons – State laws related to tattooing– Best practices– Risks– Signs of a reaction and steps to take

• CDC issued nationwide alert– Manufacturer issued voluntary recall

• Enhanced oversight needed for tattoo parlors and ink manufacturing

Case Study 2

Multistate Outbreak of Listeriosis Associated with Jensen Farms Cantaloupe --- United States, August--September 2011

MMWR October 7, 2011 / 60(39);1357-1358

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6039a5.htm?s_cid=mm6039a5_w

Multistate Listeriosis Outbreak Context and Background

• 5 sentences

• Pathogen

• Transmission

• Clinical signs and symptoms

• Public health concern

• TreatmentListeria electron micrograph.Photo: CDC/ Dr. Balasubr Swaminathan; Peggy Hayes, 2002

Multi-state Listeriosis OutbreakInitiation of Investigation

• 3 sentences

• September 2, 2011– Colorado Dept. of Public Health and Environment

reported 7 cases of listeriosis to CDC since Aug 28– Normal = 2 cases in August

• Patient interviews using Listeria Initiative questionnaires– All 7 reported eating cantaloupe– 3 reported eating Rocky Ford cantaloupe

Multi-state Listeriosis OutbreakInvestigation Methods

• 2 sentences

• Case definition

• Criteria for identifying outbreak strain of L. monocytogenes– 3 possible PFGE patterns

• Criteria for comparison group

Multistate Listeriosis OutbreakEpidemiologic Results

• Outcome information– 19 initial cases identified

• OR for cantaloupe 14.9 (95% CI 2.4, ∞)

• Cantaloupe traceback– Jenson Farms, Colorado

Multistate Listeriosis OutbreakResults

• PulseNet identified an additional, multi-state cluster with a 4th PFGE pattern associated with cantaloupe consumption

• By September 29, 2011– 83 cases in 19 states, including 15 deaths– 88% aged > 60 years– 55% female– 2 pregnant– 92% of those reporting food consumption ate

cantaloupe

Multistate Listeriosis OutbreakEpidemic Curve

Number of infections with outbreak-associated strains of Listeria monocytogenes (n = 83), by date of illness onset* --- United States, July--September 2011

Multistate Listeriosis OutbreakDiscussion and Conclusions

• Conclusion– Jensen Farms cantaloupe implicated– Voluntary recall issued

• Discussion on “unusual features”– First melon-associated listeriosis outbreak– Large outbreak associated with 4 PFGE

patterns– Large number of deaths

Multistate Listeriosis OutbreakRecommendations

• Do not eat cantaloupes from Jensen FarmsEspecially higher risk groups:– Older adults– Persons with weakened immune systems– Pregnant women

• Discard cantaloupe of uncertain origin

• Additional listeriosis advice available

Comparison of Case Study Reports

• Both outbreak reports included the major elements

• Complexity and venue of the report varies – Type of investigation – Urgency of the message– Extent of the outbreak – Audience

Summary

• Outbreak investigations are not complete without documentation in a written report

• Outbreak reports serve many purposes, both internally and externally

• Outbreak reports may differ in purpose and audience, but follow a foundational structure

References and Resources• Ashford DA, Kaiser RM, Bates ME, Schutt K, Patrawalla A, McShan

A, Tappero JW, Perkins BA, Dannenberg AL. Planning against biological terrorism: Lessons from Outbreak Investigations. Emerg Infect Dis 2003;9:515-9.

• Centers for Disease Control and Prevention. Outbreak of Invasive Listeriosis Associated with the Consumption of Hog Head Cheese – Louisiana, 2010. MMWR 2011;60(13):401-405. Available from: http://www.cdc.gov/mmwr/pdf/wk/mm6013.pdf

• Centers for Disease Control and Prevention. Hepatitis A Outbreak Associated with Green Onions at a Restaurant --- Monaca, Pennsylvania. MMWR 2003;52(47):1155-1157. Available from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5247a5.htm.

• Centers for Disease Control and Prevention. Multistate Outbreak of Listeriosis Associated with Jensen Farms Cantaloupe --- United States, August--September 2011. MMWR 2011; 60(39):1357-1358. Available from: http://www.cdc.gov/mmwr/pdf/wk/mm6039.pdf

References and Resources• Centers for Disease Control and Prevention. Multistate Outbreak of

Monkeypox---Illinois, Indiana, Kansas, Missouri, Ohio, and Wisconson, 2003. MMWR 2003;52(23):537-540. Available from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5223a1.htm

• Centers for Disease Control and Prevention. Pneumocystis Pneumonia – Los Angeles. MMWR 1981;30(21):1-3. Available from: http://www.cdc.gov/mmwr/preview/mmwrhtml/00043494.htm.

• Den Boer JW, Yzerman PF, Schellekens J, et al. A large outbreak of Legionnaires’ disease at a flower show, the Netherlands, 1999. Emerg Infect Dis 2002;8:37-43.

• Fontham ETH, Correa P, Wu-Williams A, Reynolds P, Greenberg RS, Buffler PA, et al. Lung cancer in nonsmoking women: a multicenter case-control study. Cancer Epidemiol Biomarkers Prev 1991;1:35-43.

• Gaudet, M. (2003). Suggestions for Critically Evaluating an Epidemiologic Study Report. Handout developed for Principles of Epidemiology. UNC Chapel Hill Gillings School Global of Public Health.

References and Resources• Goode B. Outbreak of E. coli 0157:H7 at the North Carolina

State Fair – 2004. EpiNotes, North Carolina Department of Health and Human Services, Division of Public Health. Accessed at http://www.epi.state.nc.us/epi/pdf/en2004-4.pdf

• Gordis, L. Epidemiology. 2nd ed. Philadelphia: WB Saunders Company; 2000.

• Greenberg RS, Daniels SR, Flanders WD, Eley JW, Boring JR. Medical epidemiology. 3rd ed. New York: McGraw-Hill; 2001.

• International Committee of Medical Journal Editors. Recommendations for the Conduct, Reporting, Editing and Publication of Scholarly Work in Medical Journals. Updated August 2013. http://www.icmje.org/ Accessed January 2, 2014.

• Last JM, editor. A dictionary of epidemiology. 4th ed. Oxford University Press; 2001.

References and Resources• Levine, S. Redinger, C. and Robert, W. (September / October

2001). Community Exposure Assessment and Intervention Effectiveness at Trinity American Corporation, Glenola, North Carolina. American Industrial Hygiene Association Journal. 62:649-657.

• Massachusetts Department of Public Health.Massachusetts Foodborne Illness Investigation and Control Reference Manual (2007). Available from: http://www.mass.gov/eohhs/gov/local-gov/foodbourne-illness/foodborne-illness-investigations-and-control.html

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• Massachusetts Department of Public Health.Massachusetts Foodborne Illness Investigation and Control Reference Manual (2007). Available from: http://www.mass.gov/eohhs/gov/local-gov/foodbourne-illness/foodborne-illness-investigations-and-control.html

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• North Carolina Division of Public Health. Conducting an Outbreak Investigation. The North Carolina Communicable Disease Control Manual. Accessed at http://epi.publichealth.nc.gov/cd/lhds/manuals/cd/outbreak.html

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