Influenza in Queensland 2013 - 2108 · Calendar week commencing 1 January 2018, was used to...

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

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© 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

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reason reliance was placed on such information.

mailto:[email protected]

http://www.health.qld.gov.au/ph/cdb/sru_influenza.asp


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


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.


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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Influenza A Influenza B Percentage positive

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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.

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Tropical Central Southern

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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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A/H1N1 A/H3N2 A/un-subtyped B A and B

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Week and month of admission


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

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Female Male Rate

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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


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.

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Week, month and year of onset

2013 2014 2015 2016 2017 2018


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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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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General admissions ICU admissions

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2013 2014 2015 2016 2017 2018


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.


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

http://www.who.int/influenza/human_animal_interface/virology_laboratories_and_vaccines/influenza_virus_infections_humans_feb14.pdf

http://www.who.int/influenza/human_animal_interface/virology_laboratories_and_vaccines/influenza_virus_infections_humans_feb14.pdf

https://www.health.qld.gov.au/publichealthact/

http://www9.health.gov.au/cda/source/rpt_4.cfm

http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-flucurr.htm/$File/2018-Season-Summary.pdf

http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-flucurr.htm/$File/2018-Season-Summary.pdf

http://www.qgso.qld.gov.au/products/tables/erp-age-sex-sa1-qld-consult/index.php

http://www.qgso.qld.gov.au/products/tables/erp-age-sex-sa1-qld-consult/index.php

http://www.influenzacentre.org/surveillance_samplesreceived.htm


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





Appendix 2

Hospital and Health Services (2017 edition) with regions

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