Influenza in Queensland 2013–2018
Influenza in Queensland 2013-2018 - 1-
Influenza Surveillance Report
Published by the State of Queensland (Queensland Health), March 2019
This document is licensed under a Creative Commons Attribution 3.0 Australia
licence. To view a copy of this licence, visit creativecommons.org/licenses/by/3.0/au
© State of Queensland (Queensland Health) 2019
You are free to copy, communicate and adapt the work, as long as you attribute the
State of Queensland (Queensland Health).
For more information contact:
Office of the Chief Health Officer\Epidemiology and Research Unit, CDB,
Department of Health, GPO Box 48, Brisbane QLD 4001, email
[email protected], phone 3328 9728.
An electronic version of this document is available at
http://www.health.qld.gov.au/ph/cdb/sru_influenza.asp
Disclaimer:
The content presented in this publication is distributed by the Queensland Government as an information source
only. The State of Queensland makes no statements, representations or warranties about the accuracy,
completeness or reliability of any information contained in this publication. The State of Queensland disclaims all
responsibility and all liability (including without limitation for liability in negligence) for all expenses, losses, damages
and costs you might incur as a result of the information being inaccurate or incomplete in any way, and for any
reason reliance was placed on such information.
Influenza in Queensland 2013-2018 - 2-
Contents
Introduction......................................................................................................... 4
Methods ............................................................................................................. 4
Data summaries ................................................................................................. 5
Influenza notifications .......................................................................................... 5 Profile of the 2018 season .......................................................................... 5 Comparison between seasons: 2013 to 2018 ............................................. 9
Influenza hospitalisations (public hospitals) ....................................................... 12
Summary .......................................................................................................... 13
References ....................................................................................................... 14
Appendices....................................................................................................... 15
Appendix 1......................................................................................................... 15
Composition of influenza vaccine for the southern hemisphere season 2013 to 2018 .............................................................................................................. 15
Appendix 2......................................................................................................... 16
Hospital and Health Services (2017 edition) with regions ................................... 16
Figures
Figure 1 Weekly influenza notifications in Queensland by type and percentage of positive tests (public laboratory system only), by week and month of testing, 1 January to 31 December 2018 ................................................ 5
Figure 2 Queensland regional influenza notifications by week and month of onset, 1 January to 31 December 2018 ...................................................... 6
Figure 3 Influenza notifications in Queensland by age group, sex and annual age group specific rates, 1 January to 31 December 2018 ......................... 7
Figure 4 Laboratory confirmed influenza admissions in Queensland residents, to Queensland public hospitals, by influenza type, subtype, and week and month of admission, 1 January to 31 December 2018 ......................... 7
Figure 5 Laboratory confirmed admissions to Queensland public hospitals by age group, sex and age group specific admission rates, 1 January to 31 December 2018 ..................................................................................... 8
Figure 6 Influenza notifications in Queensland by week, month and year of onset, 1 January 2013 to 31 December 2018 ........................................... 10
Figure 7 Influenza notifications in Queensland by type, month and year of onset and percentage of positive influenza tests (public laboratory system only), 1 January 2013 to 31 December 2018 ................................ 11
Figure 8 Influenza notification rates in Queensland by age group and year of onset, 1 January 2013 and 31 December 2018 ........................................ 11
Figure 9 Influenza admissions to Queensland public hospitals by month, year and admission type, 1 January 2013 to 31 December 2018 ...................... 12
Figure 10 Influenza admission rates to Queensland public hospitals by age group and year of admission, 1 January 2013 to 31 December 2018 ....... 12
Influenza in Queensland 2013-2018 - 3-
Tables
Table 1 Influenza season summary for Queensland 2013 to 2018 by type, subtype, and public hospital admission count ............................................. 9
Table 2 Influenza season profile for Queensland 2013 to 2018 by type, peak week and median age of notifications and hospitalisations ......................... 9
Influenza in Queensland 2013-2018 - 4 -
Introduction
Influenza is a viral respiratory disease of global public health importance. Influenza A
viruses constantly mutate, changing the year-to-year dynamics of an influenza season.
The seasonal pattern is one of outbreaks or epidemics in the winter months in
temperate regions of the world; while in tropical areas, influenza activity may increase
at any time of year. The disease varies in severity, and may be mild to moderate in
some people, but very severe in others. Infection in the very young, the elderly, and
those with underlying medical conditions, can lead to severe complications, including
pneumonia and death1.
Laboratory confirmed influenza is a nationally notifiable condition in Australia, and has
been notifiable in Queensland since 2001. In Queensland, notification is mandated
under the provisions of the Public Health Act (2005) and its subordinate Regulation2. A
case definition, which requires a positive laboratory result, is applied to identify valid
notifications. Annual influenza counts and rates vary by year and jurisdiction within
Australia3,4.
In Queensland, the influenza season typically occurs in southern and central areas
between May and October. In the tropical region, the pattern can be more variable, and
may include clusters outside this period.
The purpose of this report is to provide a descriptive data summary of the 2018
influenza season in Queensland, compared with the 2013–2017 seasons.
Methods
Data were extracted for 2013 to 2018 influenza notifications from the Queensland
Health notifiable conditions register, on 5 February 2019. Hospital admission data for
2013 to 2018 were extracted from EpiLog, a register of influenza admissions to
Queensland public hospitals, on 5 February 2019. Percentage positive data were
obtained from AUSLAB, and represent the public laboratory system only. Influenza
strain data were obtained through Forensic and Scientific Services (FSS), Health
Support Queensland, on 5 February 2019. All reported data were correct at the time of
extraction, but may be subject to change following routine data quality revisions.
Calendar week commencing 1 January 2018, was used to determine week of onset.
Week 53 includes one day: 31 December 2018.
Denominator data for rate calculations were obtained from the Queensland
Government Statisticians Office5 on 7 February 2019.
Data analyses were undertaken using Microsoft Excel 20166, SQL Server Management
Studio 20157 and RStudio version 0.99.8968.
Influenza in Queensland 2013-2018 - 5 -
Data summaries
Influenza notifications
Profile of the 2018 season
In 2018, there were 15,685 notifications of laboratory confirmed influenza in
Queensland. Influenza A viruses dominated the season, contributing 80.8% of the total
notifications. Of those influenza A viruses further characterised (n=2,088), there were
similar proportions of subtype A/H1N1 (50.8%) and A/H3N2 (49.2%).
Data from the World Health Organization Collaborative Centre for Reference and
Research on Influenza (WHOCC), indicate that the circulating strains of A/H1N1 and
both influenza B lineages, were consistent with the 2018 quadrivalent influenza
vaccine. Isolates of A/H3N2 virus appeared to be reasonably matched; however
technical issues limited the WHOCC’s capacity to fully assess these viruses9.
The epidemic curve for 2018 is shown in Figure 1. A short, sustained increasing trend
in notifications was apparent from week 33 (week beginning 13 August), reaching a
peak in week 36 (week beginning 3 September), with 688 notifications. From week 48
(week commencing 26 November), influenza activity increased again, with notification
counts remaining elevated until the end of 2018. The highest percentage of positive
influenza tests in the public laboratory system, occurred outside the typical season
(May to October), with a peak of 18.3% in week 52 (week beginning 24 December).
Figure 1 Weekly influenza notifications in Queensland by type and percentage of positive tests (public laboratory system only), by week and month of testing, 1 January to 31 December 2018
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
January February March April May June July August September October November December
Pe
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Influenza A Influenza B Percentage positive
Week and month of onset
No
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Influenza in Queensland 2013-2018 - 6 -
The statewide notification profile was largely influenced by activity in the central and
southern regions (Figure 2). Both regions experienced bimodal notification
distributions, with central region peaks in weeks 36 and 37 (309 notifications in each
week), and week 51 (226 notifications); southern region experienced peaks in week 36
(313 notifications), and week 49 (255 notifications). The tropical region experienced
influenza activity at lower levels throughout the year, with peak activity in week 33 (89
notifications).
The highest percentage positive for influenza tests (public laboratories only) in the
tropical, central, and southern regions were recorded as 18.3%, 23.0%, and 14.9%
respectively.
Figure 2 Queensland regional influenza notifications by week and month of onset, 1 January to 31 December 2018
Figure 3 shows the age and sex distribution of notifications, and the age group specific
notification rates per 100,000 population per year.
The highest age group specific notification rate was in the 80 years and older age
group, with 523.5 notifications per 100,000 population per year; followed by the five to
nine years age group, with 457.9 notifications per 100,000 population per year.
The overall mean and median age of notified cases was 39 years. More females
(54.1%) than males (45.9%) were notified with influenza.
0
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150
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300
350
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
January February March April May June July August September October November December
Tropical Central Southern
Week and month of onset
Num
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tifica
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Influenza in Queensland 2013-2018 - 7 -
Figure 3 Influenza notifications in Queensland by age group, sex, and annual age group specific rates, 1 January to 31 December 2018
Hospital admissions associated with confirmed influenza provide a useful proxy
measure for disease severity. Figure 4 summarises public hospital influenza admission
data for Queensland residents, for the 2018 season. There were two peak weeks for
hospital admission, week 36 (64 admissions), and week 52 (69 admissions).
Figure 4 Laboratory confirmed influenza admissions in Queensland residents, to Queensland public hospitals, by influenza type, subtype, and week and month of admission, 1 January to 31 December 2018
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<1 1-4 5-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+
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Age group (years)
Female Male Rate
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January February March April May June July August September October November December
A/H1N1 A/H3N2 A/un-subtyped B A and B
Num
be
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f h
osp
ital
ad
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Week and month of admission
Influenza in Queensland 2013-2018 - 8 -
Figure 5 shows the age and sex distribution of public hospital influenza admissions,
and the age group specific public hospital admission rate per 1,000 influenza
notifications.
The highest age group specific admission rate was in children aged younger than one
year (313.5 admissions per 1,000 notifications); followed by people aged 80 years and
older (260.5 public hospital admissions per 1,000 notifications).
The overall mean and median ages of public hospital admissions were 39 and 55
years, respectively. Males (49.9%) and females (50.1%) were hospitalised with similar
frequency.
Figure 5 Laboratory confirmed admissions to Queensland public hospitals by age group, sex, and age group specific admission rates, 1 January to 31 December 2018
0
40
80
120
160
200
240
280
320
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<1 1-4 5-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+
Female Male Rate
Age group (years)
Num
be
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sp
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dm
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Ad
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ate
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,00
0 influ
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no
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Influenza in Queensland 2013-2018 - 9 -
Comparison between seasons: 2013 to 2018
Influenza seasons can vary considerably from year to year, depending on a number of
factors, including which viruses are circulating. Influenza A predominated in all years in
the reporting period (Table 1) except for 2015.
During the influenza A dominated seasons, A/H1N1 was the most common subtype in
2013 and 2014; and A/H3N2 in 2016 and 2017. In 2018, there were similar proportions
of A/H1N1 and A/H3N2 detected.
Table 1 Influenza season summary for Queensland 2013 to 2018 by type, subtype, and public hospital admission count
Table 2 summarises key features of the 2013 to 2018 seasons. It is noteworthy that the
peak week across the years fell within a narrow range, between week 33 and week 36.
Table 2 Influenza season profile for Queensland 2013 to 2018 by type, peak week and median age of notifications and hospitalisations
2018 2017 2016 2015 2014 2013
Total influenza 15,685 56,590 23,284 28,061 17,898 5,509
Influenza type
A 12,670 37,712 21,434 9,768 15,307 3,570
A/H1N1 1,060 591 838 199 2,023 697
A/H3N2 1,028 2,772 2,218 1,334 875 192
Subtype unavailable 10,582 34,349 18,378 8,235 12,409 2,681
B 3,015 18,878 1,850 18,293 2,591 1,939
Victoria lineage 18 8 15 169 6 12
Yamagata lineage 125 56 26 145 21 117
Lineage unavailable 2,872 18,814 1,809 17,979 2,564 1,810
Type unavailable 0 0 0 0 0 0
Hospitalisations* 1,715 6,079 3,347 1,651 2,235 483
Annual Total Counts
*Queensland public hospitals only
Year Total notificationsInfluenza A
notifications (%)
Influenza B
notifications (%)
Peak week
(notifications)
Notifications Hospitalisations
2018 15,685 12,670 (80.8) 3,015 (19.2) 36 (688) 39 55
2017 56,590 37,712 (66.6) 18,878 (33.4) 33 (5,663) 39 65
2016 23,284 21,434 (92.1) 1,850 (7.9) 36 (1,827) 40 63
2015 28,061 9,768 (34.8) 18,293 (65.2) 34 (3,415) 28 52
2014 17,898 15,307 (85.5) 2,591 (14.5) 33 (1,753) 34 51
2013 5,509 3,570 (64.8) 1,939 (35.2) 35 (348) 38 44
Median age (years)
Annual Total Counts
Influenza in Queensland 2013-2018 - 10 -
Comparison of year to date (YTD) notification counts across years (Figure 6) at a
particular point in time can be misleading, because the start of the season can vary.
Figure 6 Influenza notifications in Queensland by week, month and year of onset, 1 January 2013 to 31 December 2018
Assessment of season severity requires consideration of more than the notification
count. As influenza transmission in the population begins to rise in the lead up to the
annual season, the percentage of laboratory tests that are positive should also rise.
During the peak month of seasonal activity, the percentage of tested specimens
positive for influenza will also reach its maximum, and has ranged between 8.0% and
46.7% during the reporting period (Figure 7).
The age distribution of influenza notifications and hospitalisations in any given season
can be influenced by the types and subtypes of circulating viruses; and may vary as the
season progresses.
Typically, the extremes of the age range, pregnant women and people with underlying
medical conditions are disproportionately affected. In addition, age sub groups within
the population may be more prone to severe disease depending on the types and
subtypes of circulating influenza virus during a particular season. Annual age specific
notification rates are shown in Figure 8.
During the reporting period, the relative proportions of influenza A and B have shown
considerable variation (Table 2). During a given season, the proportion of notifications
made up by influenza A and B is rarely constant, although overall one may dominate.
0
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
January February March April May June July August September October November December
Num
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Week, month and year of onset
2013 2014 2015 2016 2017 2018
Influenza in Queensland 2013-2018 - 11 -
Figure 7 Influenza notifications in Queensland by type, month and year of onset, and percentage of positive influenza tests (public laboratory system only), 1 January 2013 to 31 December 2018
Figure 8 Influenza notification rates in Queensland by age group and year of onset, 1 January 2013 and 31 December 2018
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2013 2014 2015 2016 2017 2018
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Influenza A Influenza B Percentage positive
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<1 1-4 5-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+
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Age group (years) and year of onset
2013 2014 2015 2016 2017 2018
Influenza in Queensland 2013-2018 - 12 -
Influenza hospitalisations (public hospitals)
Hospital admissions for influenza (Table 1, Figure 9) vary depending on season
severity. Data presented are for public hospitals only.
The highest number of hospitalisations (6,079) in the reporting period was in 2017.
Age group specific admission rates are shown in Figure 10.
Figure 9 Influenza admissions to Queensland public hospitals by month, year and admission type, 1 January 2013 to 31 December 2018
Figure 10 Influenza admission rates to Queensland public hospitals by age group and year of admission, 1 January 2013 to 31 December 2018
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2013 2014 2015 2016 2017 2018
Num
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Month and year of admission
General admissions ICU admissions
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<1 1-4 5-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+
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Age group (years)
2013 2014 2015 2016 2017 2018
Influenza in Queensland 2013-2018 - 13 -
Summary
• Influenza notifications in Queensland are monitored throughout the year.
• The pattern of influenza notifications and hospitalisations varies by year, and is
influenced by which viruses are circulating.
• The 2018 influenza season in Queensland was characterised by:
o the dominance of influenza A viruses
o a bimodal notification distribution, with increased activity in August and
September (typical seasonal months), and again in December
o low activity in the typical influenza season months (May to October)
when compared to 2014–2017
o high activity in late November and throughout December, when
compared to the same period in the previous five years.
Influenza in Queensland 2013-2018 - 14 -
References
1. World Health Organization. Influenza virus infections in humans 2014.
http://www.who.int/influenza/human_animal_interface/virology_laboratori
es_and_vaccines/influenza_virus_infections_humans_feb14.pdf
2. Queensland Government. Public Health Act. 2005.
https://www.health.qld.gov.au/publichealthact/
3. National Notifiable Diseases Surveillance System. Summary Tables.
Australian Government Department of Health.
http://www9.health.gov.au/cda/source/rpt_4.cfm
4. Australian Government Department of Health. 2018 Influenza Season in
Australia, 16 November 2018.
http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-
flucurr.htm/$File/2018-Season-Summary.pdf
5. Queensland Government Statistician’s Office (QGSO) – Australian
Bureau of Statistics consultancy for QGSO. October 2018.
http://www.qgso.qld.gov.au/products/tables/erp-age-sex-sa1-qld-
consult/index.php
6. Excel (2016). Microsoft Corporation.
7. Microsoft Visual Studio (2015) version 12.02.21005.1 REL 8. RStudio Inc version 0.99.896 9. World Health Organization Collaborative Centre for Reference and Research on
Influenza. http://www.influenzacentre.org/surveillance_samplesreceived.htm
Influenza in Queensland 2013-2018 - 15 -
Appendices
Appendix 1
Composition of influenza vaccine for the southern hemisphere season 2013 to 2018
*Quadrivalent influenza vaccine
2018A/Singapore/INFIMH-16-0019/2016 (H3N2)-like
virusB/Phuket/3073/2013-like virus B/Brisbane/60/2008-like virus
2017 A/Hong Kong/4801/2014 (H3N2)-like virus B/Brisbane/60/2008-like virus B/Phuket/3073/2013-like virus
2016 A/Hong Kong/4801/2014 (H3N2)-like virus B/Brisbane/60/2008-like virus B/Phuket/3073/2013-like virus
2015 A/Sw itzerland/9715293/2013 (H3N2)-like virus B/Phuket/3073/2013-like virus B/Brisbane/60/2008-like virus
2014 A/Texas/50/2012 (H3N2)-like virus B/Massachusetts/2/2012-like virus B/Brisbane/60/2008-like virus
2013 A/Victoria/361/2011 (H3N2)-like virus B/Wisconsin/1/2010-like virus B/Brisbane/60/2008-like virus
A/H1N1 Additional B for QIV*
Australian vaccine composition
A/California/7/2009 (H1N1)pdm09-like virus
A/H3N2 B
A/Michigan/45/2015 (H1N1)pdm09-like virus
A/Michigan/45/2015 (H1N1)pdm09-like virus
A/California/7/2009 (H1N1)pdm09-like virus
A/California/7/2009 (H1N1)pdm09-like virus
A/California/7/2009 (H1N1)pdm09-like virus
Influenza in Queensland 2013-2018 - 16 -
Appendix 2
Hospital and Health Services (2017 edition) with regions