Table 1

Definitions

General Terms


Term

Definition


Groups

Routine sets of people within which a person contacts others. School age children and teenagers belong to a set of group types that we categorized as households, extended family, before school classes or care, school classes, lunch periods, recess, after school care, clubs, sports, work, church, friends, and neighborhood.

Public Activities

Activities done either alone or as part of a group venturing out into the community where many unplanned or random contacts can occur. Public activities were categorized as passing periods within school, car rides, school and city bus rides, mall, errands, movies, concerts, sport event participation or attendance, dances, parties, and eating out.

Contact

An interaction with another person during which influenza could be passed. These must be within 3 ft and for a recognizable length of time. Contacts are divided into two types, those that occur within Groups and those that occur during Public Activities. Contacts in groups were with primary links in groups and took place for significant time, more than several minutes (often hours). Contacts in Public Activities were with primary links in the group that is doing the activity and random contacts with others (not the primary links within the group). Random contacts were for much less time than those with primary links in groups (tens of seconds to several minutes).

Contact level

Because not all contacts may be equal with respect to the spread of an infectious disease such as influenza, we defined four contact levels (all must be within 3 ft and for a recognizable length of time): 1: close, within 3 feet 2: close and talking 3: close, talking and touching 4: kissing

Primary links in groups

Within a group, a person's primary links are other people in the group that they are within 3 ft significant time, more than several minutes (often hours). For example, in a school class, a student may be in a group with 30 other students but may only be within 3 ft with the 4 people seated around them, thus the size of group would be 30 and number of primary links would be 4. Conversely, in a friend group, the student may have primary links with all others within that group.

Random contacts

Unplanned contacts where influenza could be passed that occur in public activities in public places such as school hallways, malls, movie theatres, etc. These also occur in the work environment with "customers". Random contacts are not with primary links in the group that is doing the public activity (or work). Random contacts must be within 3 ft and for a recognizable amount of time but less than a few minutes. Data on the amount of time associated with random contacts was not taken, they were defined as "in passing" (less than a few minutes, with other students in hallways and people in malls, concerts, dances, etc, or customers in the work environment).

Group Measures

Number Observations (Num Obs)

Number of groups of a particular type totaled across all individuals for the given grade (or grade range).

Number Groups per person

Average & CV for number of groups of a particular type that an average person has for the given grade (or grade range). The number of households per person can be greater than one if there are students that live at more than one household (often divorced or separated parents).

Size

Average & CV for the number of people in groups of a particular type for the given grade (or grade range).

Time per day

Average & CV for time spent in a group of a particular type per day for the given grade (or grade range).

Primary Links

Average & CV for number of primary links a person has in a group of a particular type for the given grade (or grade range).

Contact-hours per day

Average & CV for number of contact-hours a person has in a group of a particular type per day (number of primary links multiplied by the time in the group per day) for the given grade (or grade range).

Contact-level

Average & CV for contact-level of primary links in a group of a given group type for the given grade (or grade range).

Contact-level-hours per person per day

Average & CV for the number of contact-level-hours in a group of a particular type that an average person has per day for the given grade (or grade range). (Contact-hours per day for a particular group multiplied by the average contact-level for the group are first averaged for each group type. This value for each group type is then multiplied by the number of groups of this type per person.)

Public Activity Measures

Number of Observations (Num Obs)

Number of public activities of a particular type totaled across all individuals in the given grade (or grade range).

Number of Activities per person per day

Average & CV for number of public activities of a particular type that an average person has per day for the given grade (or grade range).

Time per participation

Average & CV for amount of time spent doing a particular public activity once for the given grade (or grade range).

Primary links

Average & CV for number of primary links from the group that a student does the particular public activity with for the given grade (or grade range).

Contact-hours per participation

Average & CV for number of contact-hours (primary links multiplied by time per activity) for a particular public activity done once for the given grade (or grade range).

Contact-level

Average & CV for contact-level of primary links within the group doing a public activity of this type for the given grade (or grade range).

Contact-level-hours per person per day

Average & CV for the number of contact-level-hours in a particular type of public activity that an average person has per day for the given grade (or grade range). (Contact-hours per activity for a particular activity multiplied by the average contact-level with primary links for the group the activity is done with is first averaged for each activity type. This value for each activity type is then multiplied by the number of activities of this type per person per day.)

Participating group

Group(s) that students recorded doing a public activity with. H stands for household, f for friends, and sports for sports group.

Fraction counted in groups

Fraction of students in a given grade (or grade range) who reported the time spent in a particular public activity as already counted in the time they spent with the participating group.

Random contacts per participation

Average & CV for number of random contacts a student has while participating in a particular public activity once for a given grade (or grade range).

Random contacts per person per day

Average & CV for number of total random contacts for each student in a particular public activity on a per-day basis for a given grade (or grade range).

Random contacts contact-level

Average & CV for contact-level reported for random contacts by students in a particular public activity for a given grade (or grade range).

Other terms

Per-person

Per-person values were average values for the particular grade (or grade range).

Per-day

Per-day values were formed for an average day that incorporated both week days and weekends (so that some weekday time such as in school classes was distributed to the weekend and vice versa for extra time spent on weekends with household members).


Glass and Glass BMC Public Health 2008 8:61   doi:10.1186/1471-2458-8-61

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