FluTAS 2019 Report 2

FluTAS 2019 Report 2

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Public Health Services produce the fluTAS Report to provide information about the level of influenza (flu) in Tasmania. Multiple 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 31 May 2019.

May 2019 Update

  • Community syndromic surveillance in Tasmanian suggested ongoing low levels of influenza-like illness activity, 1.8 per cent at the end of May 2019. This is higher than the average of previous years (1.6 per cent).
  • Laboratory-confirmed influenza notifications during this month continue to be higher than the same period in previous years.
  • Weekly influenza notifications decreased during May following the peak in mid-April (week 15).
  • The number of influenza tests conducted during May was twice as high as May 2018.
  • The proportion of tests positive for influenza is higher than previous years during the same period.
  • Sixty-seven patients have been admitted to the Royal Hobart Hospital with influenza between 1 April and 31 May 2019.
  • Similar higher than usual influenza activity was reported by other States and Territories during May 2019.

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.

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 online and on Facebook

FluTracking recommenced on Monday 8 April 2019; three weeks earlier than usual due to increased influenza activity across Australia. An average of 3 780 Tasmanians participated each week, an increase on 2018 participation (3 150 Tasmanians per week).

Reports of influenza-like illness (fever plus cough) in Tasmanian participants increased during May 2019 (Figure 1). One point eight per cent of Tasmanian participants reported fever plus cough during the last week of May 2019. Of these participants, 60 per cent also reported absenteeism from normal duties.

Figure 1 is a combined line and vertical bar graph. The horizontal axis indicates the months and weeks of 2019 moving left to right. The vertical axis on the left hand side is the percentage of participants reporting fever and cough. This is represented by two line graphs – one line for 2019 and one line for 2018. The line for 2018 extends from late April to late October: weeks 17 to 42. The line for 2019 covers April to May 2019 only: weeks 14 to 22. This is because FluTracking commenced three weeks earlier than usual on Monday 8 April 2019; due to increased influenza activity across Australia. Data presented indicates a relatively high proportion of participants reporting fever plus cough during the first week of April 2019: between three and three and a half per cent. This proportion declined to one point two per cent at week 19 in early May. The proportion then increased to one point eight per cent at the end of May. This trend is similar to the trend observed during May 2018. The vertical axis on the right hand side represents the number of flu notifications in Tasmania since the start of 2019. This bar graph shows increasing numbers of laboratory-confirmed influenza from the beginning of the year to a peak in week 16 of 108 flu notifications. Flu notifications have generally decreased between weeks 17 and 22.

Figure 1: Percentage of Tasmanian FluTracking participants reporting fever and cough, week ending Sunday 2 June 2019.

ASPREN (General Practice Syndromic Surveillance)

The Australian Sentinel Practices Research Network (ASPREN) includes registered sentinel General Practices (GPs) across Australia who report fortnightly on the number of patients presenting with influenza-like illness (ILI). Five GPs participate in Tasmania.  ASPREN is a joint initiative of the Royal Australian College of General Practitioners and the University of Adelaide.

For the fortnight ending Sunday 2 June 2019, ASPREN reported that in Tasmania, the average level of ILI activity was less than 4 out of 1 000 consultations. This was described as ‘baseline’ activity.

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 for a variety of reasons. Notifications represent a small proportion of the total influenza cases in the community.

There were 310 influenza notifications in Tasmania during May 2019. Between 2015 and 2018 an average of 24 cases of influenza were notified during the month of May.

Since 1 January 2019 a total of 995 cases of influenza have been notified.

Weekly influenza case numbers continued to decrease during May (Figure 2).

Figure 2 is a line graph with a horizontal axis indicating the months and weeks of the year. The vertical axis indicates the number of laboratory confirmed flu cases notified in Tasmania. Lines for each of the four years 2015, 2016, 2017 and 2018 indicate low baseline flu activity between January and May as well as between November to December. The line for each of these years indicates the peak of the flu season usually occurs between July and October. Between 2015 to 2018, 2017 was the year of highest flu activity in Tasmania with the peak (above 450 flu cases per week) occurring in week 36. The line for 2018 shows that 2018 was a year of very low flu activity with a peak of approximately 25 flu cases per week in week 40. The line for 2019 ends at week 22: the last week of May. This line indicates that weekly flu cases have been well above baseline levels since the middle of February. A peak in activity of 108 flu cases occurred in week 16 (mid-April). Weekly flu cases have since declined. There were 61 flu cases notified during week 22; the last week of May.

Figure 2: Notifications of influenza in Tasmania, by week, 1 January 2015 to Sunday 2 June 2019

Influenza testing

Influenza testing plateaued during May following the trend of increasing testing during April 2019 (Figure 3). There was an average of 359 PCR tests for influenza conducted each week during May; this was more than double the amount of testing conducted during May 2018 (average 157 tests per week). The highest number of influenza tests occurred during the last week of May 2019 (385 tests).

Proportion of tests positive for influenza

The percentage of positive tests decreased during May following the peak during mid-April (Figure 3).

The weekly proportion of tests positive for influenza at the end of May was higher than previous years. During 2014 to 2018, on average, two per cent of weekly influenza tests were positive (range 1 to 4 per cent positive).

Figure 3 is a combined line and vertical bar graph. The horizontal axis indicates the months and weeks of 2019 moving left to right. The vertical axis on the left hand side is the number of influenza 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 is currently presented for the first 22 weeks of 2019; 1 January to 2 June. The bar graph indicates steadily increasing testing in Tasmania from February to mid-April, followed by a plateau in testing during May. The greatest amount of testing occurred during the last week of May: week 22. The percentage of tests that were positive for influenza increased from late January to a peak at the end of February. The percentage of positive tests decreased during March, and then increased again to reach its greatest level of 27 per cent in week 16. The percentage of tests positive for influenza decreased during weeks 17 to 22 to 13 per cent.

Figure 3: Statewide Influenza PCR testing, 1 January to Sunday 2 June 2019.

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. Most individuals tested were from emergency department presentations and hospitalised patients to the RHH.

The number of respiratory PCR tests performed during May 2019 was the same as April (577 tests).

The most commonly detected respiratory pathogens during May 2019 were Rhinovirus (34 per cent), Influenza A virus (22 per cent) and Respiratory Syncytial Virus (RSV) (17 per cent).

Geographical distribution of activity

The majority of the 310 influenza cases during May 2019 were reported in the South (202 cases, 65 per cent). There were 85 cases (28 per cent) in the North and 23 cases (seven per cent) in the North-West.

Between 1 January and 31 May 2019 there were 766 cases in the South, 159 cases in the North and 67 cases in the North-West. Three overseas visitors have been diagnosed with influenza in Tasmania since the start of 2019.

Virology

During May 2019 most cases (287 cases, 93 per cent) were due to the Influenza A virus. The remaining 23 cases (seven per cent) were due to Influenza B virus.

A small proportion of Influenza A viruses undergo further subtyping. Since 1 January 2019 the most commonly reported (81 per cent) subtype has been Influenza A(H3N2). The H3N2 strain is associated with greater morbidity and mortality in older adults.

Influenza Severity

FluCAN (Influenza cases admitted to a Hospital)

The Influenza Complications Alert Network (FluCAN) reports on influenza-related hospitalisations and complications in sentinel hospitals Australia-wide during each influenza season. This system aims to provide an indication of severity of the influenza season and identify groups at higher risk of influenza-related hospital admission. The details of recent FluCAN activity are published in the Australian Influenza Surveillance Report (see Interstate Activity).

The Royal Hobart Hospital participates in FluCAN.

From 1 April to 31 May 2019 there were 587 hospital admissions of laboratory-confirmed influenza reported by sentinel hospitals Australia-wide. Of those admissions 38 (six per cent) were to an intensive care unit (ICU). During the week ending 31 May, FluCAN described activity across participating hospitals as ‘moderate influenza activity’.

Sixty-seven patients with influenza were admitted to the Royal Hobart Hospital. Of the 67 admissions, three were admitted to the ICU (four per cent).

Vaccine effectiveness

Influenza viruses are continually changing, making the targeting of an effective vaccine an annual challenge.

Nationally interim vaccine effectiveness estimates are determined using GP presentation and hospitalisation data (for example FluCAN, ASPREN and VicSPIN data). Vaccine effectiveness data is not yet available.

Preliminary vaccine effectiveness (VE) estimates are based on incomplete data and may change once all data from the season are collated. Final estimates are produced after the season has returned to baseline levels and are more reliable.

The estimated effectiveness of the vaccine may depend on several factors – the outcome being measured, the age group predominantly affected (vaccine effectiveness is generally lower in older people than in younger adults and children), and the match between vaccine and circulating influenza strains (generally protection against infection A/H1N1 is greater than against A/H3N2).

Interstate activity

The Australian Influenza Surveillance Report is compiled from several data sources including laboratory-confirmed notifications to National Notifiable Diseases Surveillance System, sentinel influenza-like illness reporting from general practitioners and emergency departments, workplace absenteeism and laboratory testing. The routine Australian Influenza Surveillance Report is published by the Australian Government Department of Health.

The key messages from the report describing national activity for the period 20 May to 2 June 2019 were:

  • Activity – Currently, influenza and influenza-like illness (ILI) activity are high for this time of year compared to previous years. At the national level, notifications of laboratory-confirmed influenza have increased in the past fortnight. The number of laboratory-confirmed notifications of influenza reported to the NNDSS in the 2019 year-to-date are greater when compared to the same periods in 2017 and 2018, however, this is due to heightened inter-seasonal activity.
  • Severity – There is no indication of the potential severity of the 2019 season at this time.
  • Impact – There is no indication of the potential impact on society of the 2019 season at this time.
  • Virology – In the year to date and in the past fortnight, the majority of confirmed influenza cases reported nationally were influenza A (81 per cent). Where subtyping data were available, influenza A(H3N2) was the dominant influenza A subtype in the past fortnight, however, the proportion of influenza B has been steadily increasing in a number of jurisdictions since late April.

Annual Influenza Vaccine

Composition of 2019 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):

The AIVC met on 10 October 2018 to recommend the influenza viruses to be used in influenza vaccines for 2019. The TGA accepted the recommendations of the AIVC.

This year there is a new A strain (H3N2) and a new strain for the B Victoria linage.  Influenza virus strains included in the 2019 seasonal influenza vaccines are:

  • A (H1N1): an A/Michigan/45/2015 (H1N1)pdm09 like virus
  • A (H3N2): an A/Switzerland/8060/2017 (H3N2) like virus
  • B: a B/Colorado/06/2017 like virus (not included in the trivalent vaccine)
  • B: a B/Phuket/3073/2013 like virus

Further information on the composition of influenza vaccines is available online

Is vaccination recommended?

Annual influenza vaccination is recommended for anyone over the age of six months who wishes to reduce the likelihood of influenza and its complications. Annual vaccination can help to reduce the spread of influenza and protect vulnerable members of the community.

Influenza vaccines in 2019 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 (state funded)
  • 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 see the Public Health flu page or the  Australian Government immunisation page

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

Further Information

For the latest information on influenza in Tasmania visit the Public Health flu page

Past fluTAS reports are available online