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Influenza information for health professionals

Influenza, commonly known as the flu, is a highly contagious infection of the nose, throat and lungs caused by the influenza A or B (or rarely C) viruses.

Influenza is a notifiable condition

Clinical presentation

In South Australia, influenza is most common in the winter months.

Influenza causes a spectrum of illness from asymptomatic infection to fatal pneumonia (primary viral or secondary bacterial). Severe disease is more common in pregnancy, people aged over 65 years and in people with underlying chronic disease.

Doctors should consider influenza in anyone with:

  • Fever (greater than 38oC or a good history of fever), note: fever may be absent in elderly persons
    AND
  • Cough or sore throat, in the absence of any other explanation for symptoms.

Most people with uncomplicated influenza recover within a week, although the cough and fatigue may last longer.

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Mode of transmission

Spread is via respiratory droplets and direct contact with respiratory secretions.

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Incubation period

Incubation period is 1 to 4 days (average 2 days).

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Infectious period

People infected with influenza are considered infectious from 1 day before onset of symptoms up to 7 days from onset of symptoms. Viral shedding is greatest in the first 3 to 5 days of illness. Young children may shed virus for longer, up to 7 to 10 days. Viral shedding may continue for longer in severely immuno compromised persons.

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Diagnosis

In mild illness laboratory testing is not always necessary.

Take a deep nasal or throat swab, or sputum for respiratory viral testing. Use appropriate personal protective equipment when obtaining the sample.

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Prevention

  • Encourage annual influenza vaccination. Vaccination against influenza has the primary aim of reducing severe influenza. Annual flu vaccination is strongly recommended for anyone 6 months of age and older and should be actively promoted for people at increased risk of complications.  Due to changes in circulating strains and waning immunity, vaccination is required each year.
  • Encourage respiratory etiquette and hand hygiene:
    • cover a cough or sneeze with a tissue or arm (not a hand)
    • drop used tissues immediately into a rubbish bin
    • wash hands with soap and running water, or use an alcohol based hand rub, after sneezing, coughing or touching used tissues.
  • In healthcare settings, institute contact and droplet precautions. 
  • Consider prescribing antivirals. Antivirals can be given after known exposure to influenza. Prophylactic antivirals are usually only used in persons at high risk of severe influenza. If used, prophylaxis should be commenced within 48 hours of exposure.
  • Exclude cases from childcare, preschool, school or work until there has been no fever for 24 hours (without using an antipyretic).

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Treatment

  • Medically assess the need for hospital presentation/admission.
  • consider antivirals for treatment in:
    • patients with established complications or severe illness (for instance, needing hospitalisation)
    • patients from high risk groups
    • patients not in high risk groups and not severely unwell if commenced within 48 hours of onset.
  • patients with uncomplicated influenza do not require antibiotics.

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Managing influenza  disease in pregnancy

Is your patient pregnant or has recently given birth? The Managing pregnant women with suspected influenza fact sheet (PDF 75KB) provides health professionals with information on influenza prevention, testing, treatment and prophylaxis in pregnant women.  Important considerations in influenza management during each trimester, delivery and in the post-partum period are also discussed.

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Notification

The Communicable Disease Control Branch, South Australia should be notified within 3 days of suspicion or confirmation of influenza on either on:

  • telephone: 1300 232 272
  • fax: (08) 8226 7187

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Surveillance

The Communicable Disease Control Branch conducts state-wide surveillance of all notifiable conditions (including influenza) in South Australia. This includes a chart that provides a regular update on influenza activity in South Australia.

Nationally, the Australian Influenza Surveillance Report and Activity Updates provides national data monitoring influenza activity and severity.

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2019 flu vaccine campaign resources

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