Structure of an Outbreak Investigation Report

The structure of the report follows the same structure as most scientific reports or articles. The report includes the following sections:

Summary / Abstract

In the abstract, the key features of the outbreak should be presented:

• Who was affected?
• What happened?
• Where and when did the outbreak take place?
• Why / how did it occur?

The main lessons learned should be highlighted and the main recommendations listed. Ongoing actions to control the outbreak and prevent future outbreaks should be presented and, further actions planned specified. Nothing should be included in the abstract unless already stated in the report.

Introduction and background

The introduction includes the information that will help us understanding the context and the environment. Items useful to be included are:

• population demographics
• surveillance data
• previous similar outbreaks
• description of the area/site/facility
• healthcare system
• industries involved
• any unusual point

Outbreak description

What was the initial story?

• how was the outbreak reported?
• which steps were taken to confirm it?
• what was known to date?

Why was an investigation undertaken?

• which were the objectives of the investigation?(Stopping the outbreak, identify the source and contributing factors, prevent future outbreaks, describe extent and disease burden etc)

How was the outbreak managed?

• who was on the Outbreak Management Team?
• who assisted in the investigation?
• what control measures were taken?

Methods

The methods section provides the elements to understand what was done to investigate and control the outbreak. The methods used in each of the components of the investigation should be specified.

Epidemiological:

• case definition
• case finding: source and mode of data gathering (telephone, interviews, record review, observation, etc)
• study design
• definition of groups compared
• definition of exposures of interest
• study population
• Sampling and Sample size
• data collection
• plan of analysis
• statistical test used

Laboratory:

• clinical and environmental specimens collection and analysis

Environmental studies:

• site visit and risk assessment
• trace-back

Other studies

Results

The results section includes the findings that lead to your conclusions. Results should be consistent with the methods and remain factual and neutral.

The results section should not include any explanation nor discussion that are best placed in the discussion section. See chapter Presenting Data for how to create clear tables and graphs.

Epidemiological results

• response rate
• number of cases identified
• overall attack rate (AR)
• descriptive results: epidemic curve, AR by place, AR by demographic characteristics
• what do the descriptive results suggest in terms of risk groups, source, mode of transmission, exposure?
• hypothesis generated that will be tested in the analytical studies
• analytical results: proceed reporting from general to particular.
• from univariate to bivariable to multivariable (stratification and then regression) analysis.

Laboratory findings

Findings from clinical and environmental samples.

• Molecular typing results

Environmental findings

Site inspection reports

• Results from risk assessments
• Results from food/product tracing
• Other relevant (i.e weather, flooding etc)

Discussion

The discussion section should provide an interpretation of the results: what the facts presented mean in the context of the outbreak, taking into account the methodology used and the limits encountered.

The structure of the discussion would be:

• brief summary of key results
• refutation of findings
• limitations, main problems in the study
• biases that may have lead to the observed results
• inference from analytic studies
  • viewpoints on causality
• conclusions
  • clear and logical interpretation of results
  • explain how results confirmed / disapproved hypothesis
  • explain actions taken to protect public health

Lessons learned

From the experience of the investigated outbreak, some points should be highlighted to improve future investigations. A summary of problems encountered and suggestions for improvement could be useful for participating agencies and colleagues if they will use similar approaches, methods or tools in the future.

Recommendations

Recommendations should specify what should be done to:

• control the current outbreak (e.g vaccination, remove of specific batches, water chlorination, etc )
• prevent future outbreaks (e.g. public health education, change of legislation, introduce specific control measures in food manufacturing, further research on specific topic)
• improve management of future outbreaks (e.g. who should be involved in decision making process, communication channels, inclusion of other professional with additional skills in the OCT)
• improve methods in future investigation (e.g. how to minimise bias by improving the questionnaires)

The recommendations section should be short and concise, specific, targeted (who should do what?) and realistic (with the available resources what can be done, what is acceptable).

Acknowledgements

A short paragraph mentioning other persons contributing to the investigation, but not part of the outbreak control team.

References

With the references, authors can justify facts not directly related with the outbreak under investigation.

The format of the references should allow readers to find the original documents.

For EPIET, the reference system we recommend is Vancouver. http://www.nlm.nih.gov/bsd/uniform_requirements.html

Annexes

Annexes usually include tools used to collect data, inform partners and other detailed pieces of work done during the investigation that can help in understanding what has been done.

Some examples of documents that can be included in the annexes are:

• chronology of events
• general background: maps of the site, description of the population, environmental data, etc
• outbreak control team: membership, terms of reference
• detailed results: tables with epidemiological results, laboratory results, environmental results
• epidemiological questionnaire
• information letters to patients, to physicians
• press releases

FEM PAGE CONTRIBUTORS 2007

Editor

Karin Nygård

Original Authors

Alain Moren

Marta Valenciano

Contributors

Arnold Bosman

Karin Nygård