Guidelines for the Prevention and Control of Influenza Outbreaks in Residential Care Facilities for Public Health Units in Australia

3.4 Outcome definitions

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In order to completely describe an outbreak, it is necessary to accurately record the outcomes of the cases. For influenza, these may include: recovered, pneumonia, hospitalisation and death (a case may have more than one outcome). As with the case definition, the outcome definitions may vary according to the features of the illness of that particular outbreak, and the following definitions are intended as a guide only.

3.4.1 Pneumonia

A person who:

(i) meets the case definition used during an influenza outbreak, and

(ii) develops another illness within 2 weeks of onset of influenza symptoms, characterized by:

• Chest x-ray consistent with pneumonia
  AND
• At least two of the symptoms or signs below²
  • New or increased cough
  • New or increased sputum production
  • Fever (e.g., “> 38⁰C” OR “an abnormal temperature for the resident” OR “temperature 35.5⁰C or 37.5⁰C”)
  • Pleuritic chest pain
  • New physical findings on chest examination (rhonchi, wheezes, bronchial breathing)
  • One of the following to indicate change in status or breathing difficulty:
    • New or increased shortness of breath
    • Respiratory rate >25/minute
    • Worsening functional or mental status (deterioration in resident's ability to perform activities of daily living or lowering of their level of consciousness)⁸

3.4.2 Hospitalisation

Hospitalisation can be defined as transfer of a case from the RCF to a health care facility so that an additional level of care can be provided (in some hospitals this could be in a bed in an 'emergency ward').

If a patient is treated in the emergency department but not admitted they are not considered to have been ‘hospitalised’.

3.4.3 Death

Most mortality associated with influenza is not a direct result of the influenza illness. Rather, it is mostly due to complications resulting from influenza, such as secondary bacterial pneumonia or exacerbation of pre-existing heart disease. Traditionally, the true contribution of influenza to mortality has been under-reported due to the role of influenza in these deaths being under-recognised.

Death should be attributable to influenza if it is considered so by the treating physician or anatomical pathologist. This may be specified on a death certificate, post mortem certificate, or specifically stated by the treating physician in the medical records. If the outbreak management team has a high index of suspicion that a death of a case is attributable to influenza and there is no written record of this, it is reasonable to discuss the issue with the treating physician.

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