Line Lists

Definition: A line list is a table that summarizes information about persons who may be associated with an outbreak. Each row represents a single individual, and each column represents a specific characteristic about that person. Column information includes identifying, demographic, clinical, and other epidemiological information, including risk factors possibly related to the illness.

A line list helps organize preliminary information gathered during the early part of an outbreak investigation. As the investigation progresses, the line list can be updated. Line listings can be created by hand (paper copy) or on a computer. One advantage of creating an electronic line list is that frequency distributions and epidemic curves can be generated rapidly.

The information that goes into a line list is generally collected on a questionnaire. The important elements from the questionnaire are then used to create a line list.

The Enteric Disease Supplemental Questionnaire includes information from the ill persons, including identifying demographic, clinical, and risk factor information. The CDC epidemiologist uses this information to create both the case definition and the line list. The CDC epidemiologist uses this information to create the line list.

To set up a line list (Table 1), the epidemiologist creates a table in which each row represents a case and each column represents a characteristic of the outbreak.

• Personal information (identifying information)
  • Name, address, phone number, and county of residence
• Demographic information
  • Age or date of birth, gender, race and occupation
• Illness Information
  • Date and time of onset, date and time of recovery, date of specimen collection, results of laboratory tests
  • Symptoms including diarrhea, bloody stools, vomiting, abdominal cramps, nausea, fever, and other symptoms
• Exposure Information
  • Meal location, date and time of meal, foods eaten, drinks
• Comments

Table1: Example of a line list created during an outbreak investigation

• ID = Identification Number
• Name = Person's Initials
• Age = Age in Years
• Sex = Male or Female
• OnsetD = Date of Illness Onset
• OnsetT = Time of Illness Onset
• D = Diarrhea (3 or more loose stools in 24 hours)
• N = Nausea
• V = Vomiting
• C = Abdominal Cramping
• Game = Volleyball game played between two local youth teams late Tuesday evening July 31

The line list shows that several ill individuals experienced similar symptoms around the same time after midnight on August 1st. Based on this limited information, it is highly possible that these indivduals became ill after eating something served to the teams after the game.

Example adapted from the Foodborne Illness and Outbreak Investigation Manual (March 2008)

In summary, line lists:

• Are working documents;
• Are important for organizing information during an outbreak investigation;
• Continue on until the end.