Activity
Influenza-like-illness (ILI) activity in the community remains at historically low levels in 2021. While ILI levels increased between January and May 2021, a gradual decrease has been observed since June.
Notifications of laboratory-confirmed influenza have also remained low since April 2020. In the year to date in 2021, there have been 483 notifications to the National Notifiable Diseases Surveillance System (NNDSS) in Australia, of which 21 notifications had a diagnosis date this fortnight.
Severity
There is no indication of the potential severity of the 2021 season at this time.
In the year to date, of the 483 notifications of laboratory-confirmed influenza, no influenza-associated deaths have been notified to the NNDSS.
There have been no hospital admissions due to influenza reported across sentinel hospitals sites since commencement of surveillance in April 2021.
Impact
Given the low number of laboratory-confirmed influenza notifications, low community ILI activity, and no hospitalisations due to influenza at sentinel hospital sites, it is likely there is minimal impact on society due to influenza in 2021 to date.
At-risk populations
In 2021 to date, adults aged 85 years and older, adults aged 60–69 years, children under 5 years of age, and adults aged 75–84 have the highest influenza notification rates.
Virology
To date, 64.4% of notifications of laboratory-confirmed influenza to the NNDSS were influenza A, of which 98.4% were influenza A(unsubtyped) and 1.6% were influenza A(H3N2). Influenza B accounted for 20.3% of notifications, 3.1% were influenza A and B co-infection, 0.2% were influenza C, and 12.0% were untyped.
Vaccine match and effectiveness
It is too early to assess vaccine match and effectiveness for this season.
Of the 10 samples referred to the WHOCC to date, 1 influenza B/Victoria sample was characterised as antigenically similar to the corresponding vaccine component, while 9 influenza A(H3N2) samples were characterised as antigenically dissimilar.
https://www1.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-flucurr.htm