Definitions for the 2011-2012 season

FluWatch reports include data and information from the following sources: laboratory reports of positive influenza tests in Canada (National Microbiology Laboratory), sentinel physician reporting of influenza-like illness (ILI), provincial/territorial assessment of influenza activity based on various indicators, including laboratory surveillance, ILI reporting, and outbreaks, influenza-associated paediatric and adult hospitalizations, antiviral sales in Canada, and WHO and other international reports of influenza activity.

ILI definitions for the 2011-2012 season

ILI in the general population: Acute onset of respiratory illness with fever and cough and with one or more of the following - sore throat, arthralgia, myalgia, or prostration which is likely due to influenza. In children under 5, gastrointestinal symptoms may also be present. In patients under 5 or 65 and older, fever may not be prominent.

Definitions of ILI/Influenza outbreaks for the 2011-2012 season

Schools: Greater than 10% absenteeism (or absenteeism that is higher (e.g. >5-10%) than expected level as determined by school or public health authority) which is likely due to ILI. Note: it is recommended that ILI school outbreaks be laboratory confirmed at the beginning of influenza season as it may be the first indication of community transmission in an area.

Hospitals and residential institutions: two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case. Institutional outbreaks should be reported within 24 hours of identification. Residential institutions include but not limited to long-term care facilities (LTCF) and prisons.

Other settings: two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case; i.e. workplace, closed communities.

Influenza Activity Levels Definition for the 2011-2012 season

Influenza activity levels are defined as:
1 =	No activity:	no laboratory-confirmed influenza detections in the reporting week, however, sporadically occurring ILI may be reported
2 =	Sporadic:	sporadically occurring ILI and lab confirmed influenza detection(s) with no outbreaks detected within the influenza surveillance region†
3 =	Localized:	(1) evidence of increased ILI* and (2) lab confirmed influenza detection(s) together with (3) outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in less than 50% of the influenza surveillance region†
4 =	Widespread:	(1) evidence of increased ILI* and (2) lab confirmed influenza detection(s) together with (3) outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in greater than or equal to 50% of the influenza surveillance region†
Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls. * More than just sporadic as determined by the provincial/territorial epidemiologist. † Influenza surveillance regions within the province or territory as defined by the provincial/territorial epidemiologist.