Step-By-Step Guide
Task 2.1: How to Start an Outbreak Investigation
You and your colleagues have been asked to begin your work as part of the Cocci Investigation Team (CIT).
For this task, you need to develop some initial ideas toward hypotheses to capture what is known and what needs to be uncovered in the investigation, write your case definition to identify who to include as a case-patient when you communicate the message to the medical community, and develop a questionnaire to gather pertinent data from the existing case-patients.
The steps below will walk you through this process.
- Meet with your team. Contact your mentor with questions about your team assignment.
- You may want to review the General Skills Resources link in the left menu for information on successfully forming a team.
- Your team may choose to have a team leader or may decide to have a different team structure. The choice is yours.
- Review the email from Dr. Lyons to confirm your understanding of the task.
- Download and review the document attached to Dr. Lyons’ email (14 New Case-Patient Profiles) both to see what is there and to get a feel for what resources you have available to you in this task. You may also review Ella's Discharge Summary, which was provided to you in the pre-requisite Medical Mystery rotation. (Contact your mentor if you cannot locate this document.)
- Please note: In the 14 New Case-Patient Profiles and elsewhere throughout this rotation the "Date" for each patient is listed as a number (e.g., +1 day) rather than an actual date. In a real outbreak investigation the exact date would be provided rather than a number of days. Due to the mechanics of this rotation, the day Ella Cruz became ill is used as the reference point. The "Date" other patients became ill is the number of days before (-) or after (+) the day Ella Cruz became ill.
- Each team member should download a copy of these documents and keep his/her own notes. Each of you may notice different things, which will be helpful to share with each other and discuss.
- Please note: Throughout this rotation only one set of deliverables will be submitted per team on each task. Any additional notes not captured in that set of deliverables should be retained by the team members for possible use in future tasks.
- Use the Resources link (above) to do additional research on coccidioidomycosis and outbreaks in general as needed throughout the task.
Develop List of Possible Sources for Infection
- Download and review the Hypotheses and the Scientific Method FAQ and the Hypotheses for Epidemiology FAQ in the Resources link (above) for a general understanding of the definition and goal of the hypothesis.
- As a team develop some preliminary hypotheses to guide your investigation. At this point, you are interested in opening the floor to everyone’s thoughts on what could be the source of this outbreak.
- Part of this discussion must also include what you have learned about cocci while treating Ella Cruz. How does what you know of the organism and disease affect your understanding of possible exposures? What do you think are the most likely paths of exposure for those with cocci?
- Have a team discussion about what the case-patients have in common. What do these individuals share that could have exposed them to the same organism? What are the challenges to thinking that they were exposed to the same organism? How can you reconcile these discrepancies?
- For each hypothesis list both the null hypothesis and its corresponding alternative hypothesis. See the FAQs for more information.
- Document the hypotheses your team has developed, the supporting evidence for each hypothesis, and what actions are needed to further test each hypothesis.
Tip: Remember that one piece of evidence may support multiple hypotheses, each with its own testing requirements. Organizing your notes accordingly will help track each hypothesis as the investigation develops.
Develop the Case Definition
The outbreak case definition identifies patients based on three characteristics: Person, Place and Time.
Please note: If you do internet research on the case definition, be sure to specify the “outbreak case definition.” Disease case definition follows a very different structure.
- Go to the Resources link (above) to take a look at Developing Outbreak Case Definitions and the links to some examples to see what type of characteristics that might be included.
- Work with your team to determine the following characteristics for your particular outbreak:
- "Person”
- Person can include anything about the population you’re requesting, such as gender, race, age, or symptoms – up to and including laboratory confirmed illness.
- Review Ella’s discharge summary and the case-patient profiles to find any commonalities that they share. What characteristics could help to find others who might be affected by this organism?
- “Place”
- Place specifies anything that is relevant about where the person is from or has traveled recently.
- Consider the endemic area of the organism. Are there places where patients might be located where an infection/illness is common, and therefore not part of a potential outbreak?
- Consider what you know about any cases so far. Is there a particular place that is of interest, suggesting a specific location for your case definition?
- "Time”
- Time defines the time period within which an illness would need to manifest itself in order to be considered part of an outbreak.
- Consider the incubation period of the organism and the date of your first known case. If a disease takes five weeks to incubate, and your first known case had symptoms that started ten weeks ago, would a patient who had the illness two years ago be relevant to your outbreak? Including a few incubation periods back before the first known case will help to capture other patients.
- Consider how the disease is spread. How would the time period for a disease that is spread person-to-person (e.g., the flu) be different than the time period for a disease outbreak caused by a one-time exposure from a common source (e.g., spoiled potato salad)? What time frame would there be if an item was contaminated and remained contaminated over a period of time, infecting anyone who came in contact with it? How would each of these scenarios affect the “start” and “end” points?
Trap: If a characteristic is related to a hypothesis that needs further testing, do not list the characteristic as definitive part of the case definition. If needed, a description of the characteristic as it relates to known case-patients can be included in the alert that will be sent out without using it to define a case.
- When your team has drafted the case definition, set it aside in preparation for review with your mentor when your materials are complete for this task.
Develop the Questionnaire
- To begin, take a look at Developing Questionnaires for an Epi Study in the Resources link (above). This will give you a good overview of the considerations to make when developing this questionnaire.
- Review the sample questionnaires in the Resources link (above). Use the samples as a starting point for creating your own questionnaire, but remember that a question format (level of detail, etc) used in one situation may not be relevant in all cases. Consider what information the investigators were seeking in each situation, and compare to this outbreak.
- Go through each category and decide which questions, if any, are common between the investigations.
- For example, if the sample is for a food borne illness, that may be very different from the outbreak you are investigating. In what ways could there be some of the same questions or concerns in both investigations? Talk among your team to generate some possible commonalities.
- Consider what questions might be common to most outbreaks. What are universal parameters that need to be asked, regardless of the way an outbreak is propogated?
- For questions that are definitely not common to both situations, figure out what questions might be asked instead that are more relevant to the current situation.
- For example, if the question is about what the person ate, think on a higher level. That question is really asking: What is the most common method of transmission for this organism? Be sure to include the same kind of directed question, but directed so as to gather information relevant to this investigation.
- Keep in mind that the sample questionnaires may have been used at different stages of the investigation when more information was available and therefore some questions may be more detailed than is appropriate for the current stage of this outbreak investigation.
- On the other hand if you identify that it is not likely that there is a meaningful type of question that will map to a certain line of inquiry, you are ready to move to the next section.
- Once you have drafted your questionnaire, practice with your teammates to see how long it takes to ask the questions. Remember, this will be a telephone questionnaire, so the length is important; if it is too long, you will lose respondents’ interest and investment in completing the questionnaire.
- The general rule of thumb is not to exceed 10-15 minutes for a questionnaire, even with any follow up questions that might be sparked by an unusual response. If your questionnaire goes over that time, it would be a good idea to try to take a few questions out.
Tip: When testing the questionnaire, consider testing it on someone who has not seen it before. People who were involved in the development of the questionnaire have a deeper knowledge of what is being asked and may understand a question even though the wording of the question is not clear. If other people are not available, a team can divide work in such a way that one or two members have not seen the questions and therefore can be used to test those questions.
Review and submit your work.
- Review your work.
- Did you develop a short list of ideas related to hypotheses that were well-discussed among your team members?
- Did you develop a short, precise case definition including Person, Place and Time?
- Did you develop a questionnaire that will gather the correct information accurately and quickly so as to locate the source of the outbreak most effectively?
- Submit your work.
- Review the checklist located in the Submit Your Work section of this task to ensure completion of the task before submitting your deliverables to your mentor.
- Please note: Only one set of deliverables need to be submitted per team. Any additional notes not captured in that set of deliverables should be retained by the team members for possible use in future tasks.
Resources
Task 2.1 Resources
While Wikipedia is a valuable resource, unlike some other websites anyone can contribute to or modify the site (whether they're knowledgeable about the topic or not). As a result, the site is subject to constant change by questionable sources. Be sure to cross-check information on Wikipedia with other reputable sites to ensure accuracy.
Ask the Expert
What is an outbreak, and how can you be sure that it is not an isolated case?
What are the challenges and common mistakes made early in an outbreak investigation?
General Resources
Hypotheses and the Scientific Method FAQ
This FAQ supports you in creating and testing scientific hypotheses, with examples and explanations.
Hypotheses for Epidemiology FAQ
General information on hypotheses and testing hypotheses with emphasis on epidemiology studies.
Medline Plus
A medical dictionary from Medline Plus to help with scientific terms.
Coccidioidomycosis (cocci)
Cocci Overview from CDC
Information from the Centers for Disease Control and Prevention (CDC) on cocci clinical features, transmission, risk groups, challenges, and other important info.
Cocci Overview 1
Includes common symptoms as well as tests and exams to detect the disease.
Cocci Overview 2
Includes x-rays of a cocci patient.
Cocci Overview 3
Includes a map of endemic areas (from Wikipedia).
Cocci Overview 4
Includes incubation periods, clinical signs, and communicability in both humans and animals from The Center for Food Security and Public Health at Iowa State University.
Information on Disease Outbreaks
What is an Outbreak?
A description of what constitutes and outbreak from the World Health Organization (WHO).
Steps in an Outbreak Investigation
A list of steps involved in real outbreak investigation. Note that not all of the steps will be included in this rotation.
Recent History of Outbreaks
News from WHO on disease outbreaks around the world dating back to 1996.
Healthmap
An interactive world map that shows the location and number of reports for numerous diseases for the past 30 days.
Outbreak Case Definitions
Developing Outbreak Case Definitions
A description of what outbreak case definitions are and why they are used along with guidelines and rationale for how to develop a case definition.
Sample Case Definition: Foodborne Outbreak 1
A report on a foodborne outbreak at an assisted living facility including case definitions, an epi-curve, and a descriptive epidemiology report. The case definition is in the “Methods” section on the first page.
Sample Case Definition: Foodborne Outbreak 2
A paper on a foodborne outbreak at a wedding. The case definition is in the “Methods” section.
Sample Case Definition: Dengue Fever
An example of an outbreak case definition for Dengue is in the “Description of the Outbreak.” Look for the key aspects of the definition throughout this section.
Sample Case Definition: Coccidioidomycosis
A report about a coccidioidomycosis outbreak at an archeology site. Notice the components of case definitions described in the step-by-step: person, place, and time.
Health Alert Systems
CDC Health Alert System Overview
Frequently Asked Questions about the Centers for Disease Control and Prevention’s system for notifying public health professionals about breaking health events as they occur.
WHO Alert System Overview
Information on the World Health Organization’s Epidemic and Pandemic Alert and Response system. Near the bottom of the page is a link to a video about the system (requires Windows Media Player). More detailed information on the system is available through the sub-page links on the left.
Developing Questionnaires
Developing Questionnaires for an Epi Study
Guidelines to developing a questionnaire with special considerations for studying the epidemiology of an illness.
Sample Questionnaire: FoodBorne
A sample questionnaire used for cases of foodborne illness.
Sample Questionnaire: Preeta
Questionnaire used in an investigation designed to collect information on a disease (CO – CDAD is Community Associated Clostridium Difficile Associated Disease) to figure out what the magnitude of a disease was in a certain community and determine risk factors.
Sample Questionnaire: Mycobacterium Mucogenicum
Outbreak investigation looking for the cause of a bloodstream infection to put a stop to it. The organism was known. In a hospital – questions are all around hospital exposures to find out who was getting infected and how they were getting infected.
General Questionnaire Design Guide 1
General information on designing questionnaires from Canada’s National Statistical Agency. About half way down the page are examples of different types of questions and how to avoid common wording errors.
General Questionnaire Design Guide 2
A general guide to designing questionnaires including different types of questions that can be used. General design considerations begin about half way down. Note: the site from a County Council in the United Kingdom so there may be some words/phrases that are not used in the United States.
