fluTAS 2020 Report 1

fluTAS Report

fluTAS 2020 Report 1

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Public Health Services produce the fluTAS Report to provide information about the level of influenza (flu) in Tasmania. Several surveillance data sources are used to obtain measures of influenza activity in the community.

This surveillance report describes influenza activity in Tasmania during the period 1 January to Sunday 3 May 2020 (Week 18).

2020 summary to date: 1 January to 3 May

  • There have been 155 laboratory-confirmed influenza notifications in Tasmania this year.
  • Influenza notifications are considerably lower than the same period in 2019 (681 notifications) but are higher than the same period in previous years (average 2016-2018, 100 notifications).
  • Only three cases of influenza have been reported since the week ending Sunday, April 5 (Week 14).
  • This decline in notifications coincided with the physical distancing policies, implemented by the Commonwealth and Tasmanian Governments during March 2020 in response to the COVID-19 pandemic.
  • A similar decline in influenza notifications has been observed by other States and Territories.
  • Influenza A was the predominant circulating influenza virus with 140 notifications.
  • 3 884 polymerase chain reaction (PCR) tests for influenza have been conducted so far this year.
  • The proportion of tests positive for influenza is considerably lower (5 per cent) than for the same time period last year (14 per cent).
  • Clinical severity for the season to date is currently not able to be measured.

Influenza activity

The influenza season is different almost every year. This is related to many factors including the influenza strains and subtypes that are circulating, the population groups most affected, the susceptibility of the population, and changes that may occur to the viruses during the year. Our surveillance systems at a state and national level help us to understand influenza activity and severity.

Notifications of laboratory-confirmed influenza to Public Health Services

Influenza notifications are based on positive laboratory tests. Many people with influenza-like illness choose not to attend medical care or are not tested when they attend. Notifications therefore represent a small proportion of the total influenza cases in the community.

There were 155 laboratory confirmed notifications of influenza in Tasmania from1 January to 3 May 2020 (week 18). This is 35 per cent higher than the 2016-2018 average of 100 notifications but 77 per cent lower than the 681 notifications received during the same period in 2019 due to heightened inter-seasonal activity.

Monthly influenza case numbers decreased steadily from January to March and dropped to only three cases in April (Figure 1). This decline coincided with the social distancing policies, implemented by the Commonwealth and Tasmanian Governments during March 2020 in response to the COVID-19 pandemic. A similar decline in influenza notifications has been observed by other States and Territories.

Figure 1 is a line graph with a horizontal axis indicating the 52 weeks of the year. The vertical axis indicates the number of laboratory confirmed flu cases notified in Tasmania for each week of the year.  Lines for each of the three years 2016, 2017 and 2018 each indicate low baseline flu activity between January and May as well as between November to December. The line for each year indicates that the peak of the flu season usually occurs between July and October. The line for 2017 indicates a year of high flu activity in Tasmania with a weekly peak above 450 flu cases occurring during August and September 2017. The line for 2018 indicates a year of very low flu activity with a peak of approximately 25 flu cases during early October 2018.  The line for 2019 indicates that weekly flu cases were well above baseline levels between the middle of February and the middle of July. Activity was high early in the year with a high of 109 cases mid-April. Activity then decreased and increased steadily from 1 June to mid-July before decreasing again until the start of August. Weekly flu cases peaked again with a high of 180 cases during the middle of August before decreasing to the end of the year.  The line indicating flu cases in Tasmania for 2020 shows low baseline flu activity for the year-to-date with only three cases reported since the week ending Sunday, April 5 (Week 14).

Figure 1: Notifications of influenza in Tasmania, by week, 1 January 2016 to Sunday 3 May 2020.

Influenza testing

There were 3 884 polymerase chain reaction (PCR) tests for influenza conducted between 1 January and Sunday 3 May 2020. Similarly, 3 858 tests were conducted during the same period in 2019. Influenza testing peaked at the end of April with 601 tests conducted in week 18 (Figure 2).

Proportion of tests positive for influenza

The percentage of positive tests peaked in week 2 at 14 per cent and week 5 at 13 per cent before gradually declining to no positive tests in week 14 (Figure 2). The weekly proportion of tests positive for influenza was five per cent, with a range of 0 to 14 per cent. During 2019, the weekly proportion of tests positive for influenza was 14 per cent, with a range of six per cent to 27 per cent.

Figure 2 is a combined line and vertical bar graph. The horizontal axis indicates the months and weeks of 2020 moving left to right. The vertical axis on the left-hand side is the number of influenza polymerase chain reaction or PCR tests conducted per week (represented by bars in the figure). Each bar is split into two colours: positive tests are at the bottom of the bar, with negative tests stacked on top of the bar.   The vertical axis on the right hand side is the percentage of PCR tests that are positive for influenza (represented by a line overlaid on top of the bar graph in the figure).   Data are currently presented for the first 18 weeks of 2020; 1 January to 3 May The bar graph indicates an increase in testing in Tasmania during March and April. Influenza testing peaked at the end of April with 601 tests conducted in week 18. The percentage of positive tests peaked in week 2 at 14 per cent and week 5 at 13 per cent before gradually declining to no positive tests in week 14.

Figure 2: State-wide influenza PCR testing, 1 January 2020 to Sunday 3 May 2020.

Other circulating respiratory illness

Many viruses cause the ‘common cold’ and ‘influenza-like illnesses’. The Royal Hobart Hospital (RHH) laboratory performs a PCR test that detects influenza A and B viruses, as well as seven other respiratory pathogens commonly associated with respiratory illness.

There were 1 666 PCR tests performed by the RHH during the first quarter of 2020. Similarly, 1 620 tests were performed during the same 18-week period of 2019.

The most commonly detected respiratory pathogens during 1 January to 3 May 2020 were Rhinovirus 58 percent), Parainfluenza (13 per cent) and Influenza A virus (9 per cent).

Geographical distribution of activity

Most cases (97 cases, 63 per cent) were reported in the South, 33 cases (21 per cent) in the North and 22 cases (14 per cent) in the North-West. Three overseas visitors were diagnosed with influenza in Tasmania during this period.

Figure 3 is a line graph with a horizontal axis indicating the 52 weeks of the year. The vertical axis indicates the number of laboratory confirmed flu cases notified in each region of Tasmania for each week of the year. Lines for each of the three regions, North, North-West and South, show that most cases were reported in the South with 21% of cases reported in the North and 14% of cases reported in the North-West.

Figure 3. Weekly notifications in Tasmania by Region from January 1 to Sunday May 3, 2020.

Virology

Most cases (140 cases, 90 per cent) were due to the Influenza A virus. A small proportion of Influenza A viruses undergo further subtyping. Of those subtyped, 94 per cent were Influenza A(H3N2), a strain associated with greater morbidity and mortality in older adults. The remaining 15 cases (ten per cent) of influenza were due to Influenza B virus.

Influenza-like illness

FluTracking (Community Syndromic Surveillance)

FluTracking is a national, weekly online survey that asks participants to report whether they have had fever and/or cough in the preceding week. It is a joint initiative of the University of Newcastle, Hunter New England Population Health and the Hunter Medical Research Institute. FluTracking information is available on the FluTracking website and on FluTracking Facebook page

Annual Influenza Vaccine

Composition of 2020 influenza vaccines

The annual influenza vaccine is reviewed late each year, aiming to produce vaccines for the following year that provide protection from influenza strains likely to be common during winter. Advice on the formulation of annual influenza vaccines is provided to the Therapeutic Goods Administration (TGA) by the Australian Influenza Vaccine Committee (AIVC).

This AIVC recommendation for the composition of influenza vaccines for Australia in 2020 introduces a new A (H1N1) like virus strain, a new A (H3N2) like virus strain and new strain for the B Victoria lineage when compared to the composition of the trivalent and quadrivalent vaccines for Australia in 2019.

Further information on the composition of influenza vaccines is available on the TGA website

Is vaccination recommended?

Annual influenza vaccination is the most important measure to prevent influenza and its complications and is recommended for all people ≥6 months of age. Annual vaccination can help to reduce the spread of influenza and protect vulnerable members of the community.

Influenza vaccines in 2020 are free# in Tasmania for people at greater risk of contracting and developing severe complications from influenza. Free vaccine is available through General Practitioners for the following people:

  • All children aged from six months to under five years
  • All Aboriginal and Torres Strait Islander people aged 6 months and over
  • Adults aged 65 and over
  • Pregnant women at any stage in their pregnancy
  • Adults and children aged from 6 months with chronic medical conditions such as heart, lung, liver or kidney diseases, asthma, diabetes, cancer, impaired immunity and neuromuscular conditions

For more information visit fluTAS or the Australian Government Immunisation webpage

# Please note there may be a consultation fee for the healthcare provider to administer the vaccine.

Further Information

View the latest information on influenza in Tasmania

Past FluTAS reports are available on the Communicable Diseases Prevention Unit webpage