Influenza information for health professionals

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

Influenza is vaccine-preventable and annual vaccination is strongly recommended for anyone aged 6 months and older, due to seasonal influenza strain mutations and waning immunity.

Funded vaccines are available each year for administration from April in advance of the peak influenza season in winter, which generally extends from May to September.

Medical practitioners are required to notify influenza to the Communicable Disease Control Branch (South Australia) ONLY where:

  1. they suspect a person has died from the condition, or
  2. they have conducted a point of care test that has returned a positive result which is not also reported by a pathology service.

If one or both of these scenarios apply, notify online or download and fax the purple notification form (PDF 1028KB) to (08) 7425 6696.

Note: there is a still a requirement for medical practitioners to notify avian influenza in humans. Telephone: 1300 232 272.

Funded immunisation programs for the 2026 influenza season

The following funded influenza vaccination programs will be available in 2026:

  1. Annual National Immunisation Program (NIP) vaccines for at-risk Medicare-eligible individuals, including for people experiencing homelessness (under the state funded program)
  2. The South Australian Nasal Spray Influenza Vaccination Program provides an additional vaccine option to protect children aged 2 to less than 5 years against influenza.

Clinical guidance for the 2026 influenza season

At-risk individuals eligible for the funded NIP influenza vaccines

Severe influenza disease and hospitalisation due to complications is more common for the following at-risk groups in the community (who are eligible for the funded vaccines if Medicare-eligible):

Influenza complications in this age group requiring hospitalisation are more likely than other ages and include serious respiratory complications. This age group repeatedly have the highest number of reported cases each year second only to children aged 5-9 years.

First Nations people are at higher risk of complications and being hospitalised from influenza.

Pregnant women who get an influenza infection late in their pregnancy are more likely to experience complications or have a preterm baby.

Vaccinating during pregnancy also protects babies < 6 months of age who are at high risk of serious complications and hospitalisation from influenza.

The Managing pregnant women with suspected influenza fact sheet (PDF 100KB) 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.

Adults over 65 years are more likely to be hospitalised and affected by complications from influenza, such as pneumonia.

People with certain medical conditions are more likely to have complications from influenza. These medical conditions include:

  • cardiac disease
  • chronic respiratory conditions (including severe asthma)
  • chronic neurological conditions that increase the risk of respiratory infection (including hereditary and degenerative central nervous system diseases and seizure disorders)
  • immunocompromising conditions (including immunocompromised due to disease or treatment)
  • diabetes and other metabolic disorders
  • renal disease
  • haematological disorders (including haemoglobinopathies)
  • children aged 6 months to 10 years on long term aspirin therapy who are at increased risk of Reye syndrome following influenza infection.
  • For more information see the People with medical conditions that increase their risk of influenza section of the Influenza chapter in the Australian Immunisation Handbook.

Adults and children who are experiencing homelessness are also eligible to receive the funded vaccines under the state funded program.  

*If a person experiencing homelessness is pregnant or in one of the at-risk age groups, they should receive the funded NIP influenza vaccines instead.

Influenza vaccine dose recommendations

One influenza vaccine per year is routinely recommended for most people.

The following groups may require multiple doses:

Receiving an influenza vaccine for the first time are recommended to have two doses at least four weeks apart to improve their immune response. If a child received at least one influenza vaccine in a previous year, they only need one dose in the following years.

Vaccinated against influenza early in their pregnancy in a previous influenza season are recommended to receive the current seasonal vaccine dose if it is available before their baby is born.

Pregnant women vaccinated against influenza in a previous season prior to becoming pregnant are recommended to receive the current seasonal vaccine dose during their pregnancy to protect their baby.

May also need two doses. 

Refer the Seasonal: 2026 Annual Funded Influenza Program - South Australia Schedule (PDF 65KB).

Clinical presentation

Influenza is highly contagious and causes a spectrum of illness – even in healthy people – from asymptomatic infection to fatal pneumonia (primary viral or secondary bacterial).

Health professionals should consider influenza in anyone with:

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

Severe disease is also more common for older people living in residential aged care facilities (RACF). See Influenza guidelines and resources for health professionals.

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

Incubation period is one to four days (average two days).

People infected with influenza are considered infectious from one day before onset of symptoms up to seven days from onset of symptoms. Viral shedding is greatest in the first three to five days of illness. After five days, the level of infectiousness is probably very low. Young children may shed virus for longer, up to seven to ten days. Viral shedding may continue for longer in severely immunocompromised persons.

Laboratory testing is not always necessary in the case of mild illness.

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

To prevent the spread of influenza, exclude cases from childcare, preschool, school or work until there has been no fever for 24 hours (without using an antipyretic).

Consider prescribing antivirals for post exposure prophylaxis. 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.

Medically assess the need for hospital presentation/admission.

Consider antivirals for treatment in:

  • people with established complications or severe illness (for instance, needing hospitalisation)
  • people from groups at risk of complications of disease
  • people not in the at-risk groups and not severely unwell if commenced within 48 hours of onset.

Vaccine ordering and administration

All health professionals registered as immunisation providers with the SA Health Vaccine Distribution Centre (VDC) will have access to all  influenza vaccines made available through the funded influenza programs. See Vaccine ordering and storage.

Keep up-to-date with all immunisation updates and program recommendations from the SA Health Immunisation Section and report influenza vaccines administered to the Australian Immunisation Register (AIR).  See Immunisation provider information.

Pharmacist immunisers

See Pharmacist immunisers for general information and guidance to deliver safe and high-quality vaccine services and other relevant information. 

Surveillance

The Communicable Disease Control Branch conducts statewide 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.

For national data see the National Notifiable Diseases Surveillance System (NNDSS) dataset - influenza (laboratory confirmed).