Influenza

Annex 4 of the Interim WHO guidance for the surveillance of human infection with A(H1N1) virus

Qualitative indicators, to be reported by all Member States

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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.
- 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).
- No information available: no information available for the previous 1-week period.

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.
- No information available.

Intensity

The intensity indicator is an estimate of the proportion of the population with acute respiratory disease, covering the spectrum of disease from influenza-like illness to pneumonia.

- Low or moderate: a normal or slightly increased proportion of the population is currently affected by respiratory illness.
- High: a large proportion of the population is currently affected by respiratory illness.
- Very high: a very large proportion of the population is currently affected by respiratory illness.
- No information available.

Impact

Impact refers to the degree of disruption of health-care services as a result of acute respiratory disease.

- Low: demands on health-care services are not above usual levels.
- Moderate: demands on health-care services are above the usual demand levels but still below the maximum capacity of those services.
- Severe: demands on health care services exceed the capacity of those services.
- No information available.