Indicators of influenza activity: 2009-2010 influenza season

Geographical spread

Geographical spread refers to the number and distribution of sites reporting influenza activity.

• No activity: no laboratory-confirmed case(s) of influenza, or evidence of increased or unusual respiratory disease activity.
• Sporadic: isolated cases of laboratory confirmed influenza infection*
• Localized: limited to one administrative unit of the country (or reporting site) only.
• Regional: appearing in multiple but <50% of the administrative units of the country (or reporting sites).
• Widespread: appearing in ≥50% of the administrative units of the country (or reporting sites).

* This indicator is not included in the global reporting.

Trend

Trend refers to changes in the level of respiratory disease activity compared with the previous week.

• Increasing: evidence that the level of respiratory disease activity is increasing compared with the previous week.
• Unchanged: evidence that the level of respiratory disease activity is unchanged compared with the previous week.
• Decreasing: evidence that the level of respiratory disease activity is decreasing compared with the previous week.

Important: this indicator is the old 'EuroFlu' Clinical activity indicator which is used for the purpose of comparison with historical data

It is an estimate of the proportion of the population with acute respiratory disease, covering the spectrum of disease from influenza-like illness to pneumonia. It is based on the overall level of clinical influenza activity in the country or region and is assessed based on the historical data at its disposal. Some countries have established numeric thresholds that define the different intensity levels of influenza activity.

• Low: no influenza activity or influenza at baseline* levels (Reported as Low or Moderate at the global level)
• Medium: usual levels of influenza activity (Reported as Low or Moderate at the global level)
• High: higher than usual levels of influenza activity
• Very high: particularly severe levels of influenza activity

* Baseline influenza activity is the level that clinical influenza activity remains in throughout the summer and most of the winter.

Impact refers to the degree of disruption of health-care services as a result of acute respiratory disease. Countries are encouraged to use the impact indicator to reflect the current surge on hospital and ICU services. Existing surveillance in the outpatient/GP setting (see the intensity indicator above) provides ample indication of impact of influenza in outpatient settings.

• Low: the surge on the patient care capacity of hospitals and/or ICUs is low relative to the total capacity of the system. The patient care capacity has not been exceeded in any hospitals or ICUs as a result of pandemic H1N1 (2009).
• Moderate: the patient care capacity of some hospitals and/or ICUs is "busy but coping". Hospitals/ICUs are very near capacity or at capacity in some areas. Modification of routine procedures, such as cancellation of elective surgeries, has been required to accommodate a surge of hospitalized or ICU patients in some areas.
• Severe: the patient care capacity of some hospitals or ICUs has been exceeded in some areas. Strategies to supplement, or divert care from, over-capacity hospitals have been implemented.

More information on the intensity and geographical levels of influenza activity reported by EuroFlu can be found at: http://www.euroflu.org/eiss_db/documents/EISS_Technical_note-clinical_data_reported_by_EISS.pdf