Australian influenza report 2010 - 19 - 25 June 2010 (#25/10)

The Australian Influenza Report is compiled from a number of data sources, including laboratory-confirmed notifications to NNDSS, sentinel influenza-like illness reporting from general practitioners and emergency departments, workplace absenteeism, and laboratory testing. A more in-depth annual report is also published in Communicable Diseases Intelligence.

Page last updated: June 2010

Report No. 25
Week ending 25 June 2010

A print friendly version of this report is available as a PDF (202 KB)

The Department of Health and Ageing acknowledges the providers of the many sources of data used in this report and greatly appreciates their contribution.

Key Indicators

Influenza activity and severity in the community is monitored by the following surveillance systems:
Is the situation changing?Indicated by trends in:
laboratory confirmed cases reported to the National Notifiable Diseases Surveillance System;
GP Sentinel influenza-like illness (ILI) Surveillance;
emergency department (ED) presentations for ILI;
ILI-related absenteeism and call centre calls: and
sentinel laboratory test results.
How severe is the disease, and is severity changing?Indicated by trends in:
hospitalisations, ICU admissions and deaths from sentinel systems; and
clinical severity in hospitalised cases and ICU admissions.
Is the virus changing?Indicated by trends in:
drug resistance; and
gene drift or shift from laboratory surveillance.

Summary

  • Levels of influenza-like illness (ILI) in the community show signs of increasing through some surveillance systems (ASPREN, WA and NSW Emergency Departments and NHCCN calls).
  • Reporting from laboratories suggests that influenza activity is increasing. However, influenza still accounts for only a small proportion of the respiratory viruses circulating in the community. The most common respiratory viruses diagnosed by sentinel laboratories this reporting period were respiratory syncytial virus (RSV) in WA, picornavirus in VIC and RSV and rhinovirus in NSW.
  • NT have reported a significant cluster of pandemic (H1N1) 2009 cases in the East Arnhem region, including 29 cases and two hospitalisations.
  • Of the 996 confirmed cases of influenza of all types diagnosed during 2010 up to 25 June, 101 (10.1%) have been sub-typed as pandemic (H1N1) 2009, 767 (77.0%) as influenza type A not sub-typed, 8 (0.8%) as A/H3N2 and 6 (0.6%) as type A&B. A further 95 (9.5%) have been characterised as influenza type B and 18 (1.8%) have been untyped.
  • Separate laboratory reporting suggests a higher level of A(H3N2) in the community, particularly in WA.
  • Sentinel hospitals have reported one hospitalisation for influenza during this period. ANZICS reported no ICU admissions for influenza.
  • In 2010, there have been 101 confirmed cases of pandemic (H1N1) 2009 influenza reported in Australia, bringing the total of confirmed cases to 37,737 since May 2009. There have been ten new confirmed cases of pandemic (H1N1) 2009 influenza diagnosed and reported in Australia (Qld, NT and WA) during this reporting period.
  • In China, influenza B accounted for 77.8% of influenza viruses detected in the week to 20 June 2010. Of these, approximately 44.1% are the same strain as that in the 2010 Southern Hemisphere vaccine.
  • As at 13 June 2010, the WHO Regional Offices reported over 18,209 deaths associated with pandemic (H1N1) 2009 influenza worldwide. Overall pandemic influenza transmission remains low.

1. Influenza activity in Australia

Laboratory Confirmed Cases

Pandemic influenza activity remains low and sporadic cases of pandemic influenza continue to be reported without evidence of sustained community transmission (Figure 1). There were ten laboratory confirmed pandemic (H1N1) 2009 cases (6 cases in NT, 1 case in SA and 3 cases in WA) diagnosed during this reporting period. All cases from the NT outbreak are not yet reflected in NNDSS.

In the same period, 26 confirmed cases of influenza have been diagnosed. They included 19 of type A not sub-typed (1 in NSW, 1 in ACT, 3 in SA and 14 in QLD), five of type B (2 in QLD, 2 in SA, 1 in Tas) and two untyped (WA).

Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 and total influenza in Australia, to 25 June 2010
Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 and total influenza in Australia, to 25 June 2010

Note: Total influenza series starts on 1 January 2010.
Source: NetEpi (2009; NSW 2010) and NNDSS (2010)


There have been 996 confirmed cases of influenza of all types diagnosed during 2010 up to 25 June. Of those, 101 (10.1%) have been sub-typed as pandemic (H1N1) 2009, 767 (77.0%) as influenza type A not sub-typed, 8 (0.8%) as A/H3N2 and 6 (0.6%) as type A&B. A further 95 (9.5%) have been characterised as influenza type B and 18 (1.8%) have been untyped (Figure 2).

Influenza type A not further sub-typed is the predominant type in Australia to date this year. While it is expected that the majority will be pandemic (H1N1) 2009, these cases have a higher age profile (median age 42 years) than cases confirmed with the pandemic (H1N1) 2009 strain (29 years in 2010). The proportion of women among people diagnosed with Influenza type A not further sub-typed is also higher (50.6%) compared to that diagnosed with the pandemic (H1N1) 2009 strain (48.5%) in 2010.

Figure 2. Laboratory confirmed cases of influenza (pandemic (H1N1) 2009 and seasonal) in Australia, 1 January 2010 to 25 June 2010, by week and type
Figure 2. Laboratory confirmed cases of influenza (pandemic (H1N1) 2009 and seasonal) in Australia, 1 January 2010 to 25 June 2010, by week and type

Source: NNDSS and NetEpi (NSW).


Influenza-Like Illness

Sentinel General Practice Surveillance

In the week ending 20 June 2010, national ILI consultation rates to sentinel GPs remained low and trending upwards, with the presentation rate approximately seven cases per 1,000 consultations (Figure 3). Eighty-four GPs reported through ASPREN, and 87 GPs through VIDRL, this reporting period.

Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2007 to 20 June 2010*
Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2007 to 20 June 2010*

* Delays in the reporting of data may cause data to change retrospectively. As data from the VIDRL surveillance system is combined with ASPREN data for 2010, rates may not be directly comparable across 2007, 2008 and 2009.
SOURCE: ASPREN, and VIDRL GP surveillance system.


WA Emergency Departments

Respiratory viral presentations reported in Western Australian EDs continue to show an upward trend (Figure 4).

Figure 4. Number of respiratory viral presentations to Western Australia EDs from 1 January 2007 to 20 June 2010 by week
Figure 4. Number of respiratory viral presentations to Western Australia EDs from 1 January 2007 to 20 June 2010 by week

Source: WA 'Virus Watch' Report


NSW Emergency Departments

In the week ending 11 June 2010, ILI presentations to NSW EDs remained low and similar to levels seen at the same time in 2008 (Figure 5). In the month of May 2010, there were 187 ILI presentations to NSW ED's, which was an increase from 150 in April 2010 but lower than the count of 915 for May 2009. There were 14 admissions to hospital following presentation to emergency departments with ILI in May 2010.

Figure 5: ILI presentations to NSW EDs from 2007-2010, by week.
Figure 5: ILI presentations to NSW EDs from 2007-2010, by week.

Source: NSW Health 'Influenza Weekly Epidemiology Report


Geographic spread of influenza and ILI – Jurisdictional Surveillance

In the fortnight ending 25 June 2010, influenza and ILI activity as reported by state and territory Health Departments indicated that there was 'sporadic' activity in all states except for NT(Figure 6).

NT reported 'local' activity with a significant cluster (29 confirmed cases) of pandemic (H1N1) 2009 in the East Arnhem region. Most of the cases are non-Indigenous and only two had been immunised. There were two hospitalisations associated with this outbreak but both have since been discharged. All cases from the NT outbreak are not yet reflected in NNDSS.

'Sporadic' activity is defined as small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak during the reporting period, but no increase in cases in syndromic surveillance systems. 'Local' activity is defined as outbreaks of influenza or increases in cases in syndromic surveillance systems and recent laboratory-confirmed influenza in a single region of the state.

Figure 6. Map of influenza and ILI activity, by state and territory, during fortnight ending 25 June 2010
Figure 6. Map of influenza and ILI activity, by state and territory, during fortnight ending 25 June 2010

Flutracking

Flutracking, a national online system for collecting data on ILI in the community, reported that ILI levels decreased in the week ending 27 June 2010 (Figure 7).

Figure 7. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week, from week ending 6 June 2009 to week ending 27 June 2010.
Figure 7. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week, from week ending 6 June 2009 to week ending 27 June 2010.

Source: Flutracking Interim Weekly Report


National Health Call Centre Network

The number of calls to the National Health Call Centre Network (NHCCN) continued to increase this reporting period (Figure 8).

The case definition for ILI calls to the National Health Call Centre Network (NHCCN) has changed recently in order to include ILI-related calls in children under 15 years of age, which were not being included in the previous case definition due to a change in recording calls by the service provider. The new case definition includes more caller groups, and as such total call numbers have increased for both 2009 and 2010.

Although ILI-related calls have been increasing gradually from the start of 2010, the number of ILI calls, and percent of total calls, remain at levels similar to late 2009 (Figure 8). Call numbers cannot be compared between early 2009 and early 2010 as not all call centres were online in early 2009. The difference in operating call centre numbers accounts for this apparent increase in recorded ILI calls (and baseline levels) between the two years.


Figure 8. Number of calls to the NHCCN related to ILI, Australia, 1 January 2009 to 25 June 2010
Figure 8. Number of calls to the NHCCN related to ILI, Australia, 1 January 2009 to 25 June 2010

Note: national data does not include QLD and VIC
Source: NHCCN data


Deaths associated with influenza and pneumonia

Death registration data show that for the week ending 4 June 2010, there were 81 pneumonia or influenza deaths per 1,000 deaths in NSW, which is below the seasonal threshold of 119 per 1,000 (Figure 9).

Figure 9. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2005 to 4 June 2010.
Figure 9. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2005 to 4 June 2010.

Source: NSW 'Influenza Monthly Epidemiology Report'


Absenteeism

In the week ending 16 June 2010, national absenteeism decreased, and was similar to levels seen at the same time in previous years (Figure 10).

Figure 10. Rates of absenteeism (greater than 3 days absent on sick leave), national employer, from 28 January 2007 to 16 June 2010, by week.
Figure 10. Rates of absenteeism (greater than 3 days absent on sick leave), national employer, from 28 January 2007 to 16 June 2010, by week.

SOURCE: Absenteeism data


Sentinel Laboratory Surveillance - confirmed influenza notifications

Results from sentinel laboratory surveillance systems for this reporting period show that 3.3% (15/449) of the respiratory tests conducted over this period were positive for influenza, compared with 2.2% last reporting period (Table 1).
Table 1. Laboratory respiratory tests that tested positive for influenza
ASPREN – national
NSW NIC
WA NIC
NT
(Reported by WA NIC)
VIC NIC
TAS laboratories
Number of specimens tested
32
102
174
N/A
118
23
Number tested which were Influenza A
1
0
12
0
1
0
    Number tested which were pandemic (H1N1) 2009
1
0
7
0
0
0
    Number tested which were seasonal A/H1N1
0
0
0
0
0
0
Number tested which were A/H3N2
0
0
5
0
1
0
    Number tested which were Influenza A untyped
0
0
0
0
0
0
Number tested which were Influenza B
1
0
0
0
0
0
The most common respiratory virus detected
RSV
RSV &
rhinovirus
RSV
N/A
picornavirus
N/A

2. Overview of influenza severity to 18 June 2010 1


While pandemic (H1N1) 2009 is generally considered a mild disease at the community level, it has had serious consequences for some who experience it. Figures of hospitalisations, ICU admissions and deaths are currently used as indicators of the severity of the disease in Australia (Table 2).

Pandemic (H1N1) data for 2009 are currently being finalised through cleaning and validation processes. It is possible that these processes will result in some changes in the data presented here. Validated data will be progressively reported as these steps are completed.

There have been a total of 37,737 confirmed cases of pandemic (H1N1) 2009 in Australia as at 11 June 2010, including 191 pandemic influenza-associated deaths. Of these, 37,636 cases were reported in 2009 and 101 cases were reported in 2010.

Table 2. Summary of severity indicators of pandemic (H1N1) in Australia, 2009 and 2010 up to 25 June 2010
2009#2010a
Confirmed pandemic
(H1N1) 2009 cases
Hospitalised cases ICU casesDeaths Confirmed (H1N1) 2009 cases
Total number37,63613% (4,992/37,636) confirmed cases)14%
(681/4,992 hospitalisations)
191101
Crude rate per 100,000 population172.122.83.10.90.5
Median age (years)213144^53^29
Females51% (19,139/37,636) 51% (2,528/4,992)53%
(364/681)
44%48.5%
(49/101)
Vulnerable groups (Indigenous persons, pregnant women & individuals with at least 1 co-morbidity)n/a58% (2,892/4,992)74%
(504/681)
67%n/a
Indigenous people~11% (3,877/34,750)20%
(808/4,048)
19%
(102/533)
13%4.1%
(3/74)
Pregnant women*n/a27%
(287/1,056 hospitalised females aged
15-44 years)
16%
(47/289) hospitalised pregnant women)
4% n/a
Cases with at least 1 co-morbidityn/a46% (2,303/4,992)67%
(457/681)
62%n/a
aData for 2009 from NetEpi, Data for 2010 from NNDSS and NetEpi (NSW).
#Data are extracted from a number of sources depending on the availability of information. Figures used in the analysis have been provided in parentheses. Data are not always complete for each summarised figure.
~The denominator for this row is the number of confirmed cases for which Indigenous status is known. In 2010, 27 cases had Indigenous status unknown.
*Includes women in the post-partum period.
^Validation of data has identified anomalies affecting median ages for ICU cases and deaths in reports #28-33 2009 and report #1 2010. Correction has resulted in a change in the median ages of ICU cases and deaths from report #2, 2010.

1Note that while the analysis of severity is on-going, updates are presented as required when there are significant changes detected. With the current low levels of pandemic (H1N1) 2009 influenza activity in Australia it is anticipated that the indicators of pandemic severity will not vary significantly.


Influenza Hospitalisations

The Influenza Complications Alert Network (FluCAN) reported one pandemic (H1N1) 2009 influenza hospitalisation from selected hospitals for the week ending 25 June 2010. For the period of 1 March to 25 June 2010, FluCAN has reported a total of 11 influenza hospitalisations (Table 3 and Figure 11). Of those, six have been associated with pandemic (H1N1) 2009, including three with ICU admission.

Table 3. Number of influenza hospitalisations, sentinel hospitals, Australia, 1 March to 25 June 2010
Type of influenzaWeek ending

25 June 2010

Total

1 March – 25 June

Pandemic (H1N1)16
Type A/H302
Type B02
Type A not subtyped01
All types011

Source: Influenza Complications Alert Network (FluCAN). Data are from 11 sentinel hospitals from all jurisdictions except NT.


Figure 11. Number of influenza hospitalisations, sentinel hospitals, Australia, 1 March to 25 June 2010
Figure 11. Number of influenza hospitalisations, sentinel hospitals, Australia, 1 March to 25 June 2010

Source: FluCAN data from 11 sentinel hospitals in all jurisdictions except NT


Intensive care

The Australian and New Zealand Intensive Care Society (ANZICS) has reported a total of seven ICU admissions for influenza in 2010, and none for this reporting period. Of these, three have been associated with pandemic (H1N1) 2009 influenza and four with Type A not further sub-typed (Figure 12).

Figure 12. Number of ICU admissions for influenza, ANZICS, Australia, 1 January to 25 June 2010
Figure 12. Number of ICU admissions for influenza, ANZICS, Australia, 1 January to 25 June 2010

Source: Australian and New Zealand Intensive Care Society (ANZIC) data base


3. Virology

Antigenic characteristics - WHO Collaborating Centre for Reference & Research on Influenza (WHO CC) in Melbourne

From 1 January 2010 to 27 June 2010, there were 52 Australian influenza isolates subtyped by the WHO CC (Table 4).

Table 4. Typing of influenza isolates from the WHO Collaborating Centre, from 1 January 2010 to 27 June 2010
Type/SubtypeACTNSWNTQLDSATASVICWATOTAL
A(H1N1)000000000
Pandemic (H1N1) 200911370191133
A(H3N2)000000448
B0100009111
Total123701221652

SOURCE: WHO CC
Please note: There may be up to a month delay on reporting of samples.
Isolates tested by the WHO CC are not necessarily a random sample of all those in the community, hence proportions of pandemic (H1N1) 2009 to seasonal are not representative of the proportions circulating.


Antigenic characterisation of 13 Pandemic (H1N1) 2009 isolates has shown 12 to be the A/California/7/2009-like strain and one a low reactor version of this strain. Antigenic characterisation of 1 type A/H3N2 isolate has shown to be the A/Perth/16/2009-like low reactor version of the strain.

International Updates

In the week ending 12 June 2010, based on FluNet reporting by National influenza Centres from 23 countries, 69.4% of positive specimens were typed as influenza B and 30.6% were typed as influenza A. In the Northern Hemisphere, the number of influenza type B detections exceeded that of influenza A. Influenza B detections were particularly high in China (69.8% of all influenza detections) and the Russian Federation (93.7%). In the Southern Hemisphere, the detection of influenza A increased, with the proportion of A(H3N2) exceeding that of pandemic A(H1N1). 1

In China, influenza B accounted for 77.8% of all influenza viruses detected in the week to 20 June 2010. From 1 January 2010 to 20 June 2010, 2864 influenza B viruses have been antigenically characterised. Of those, 2570 (89.7%) were B/Victoria viruses, including 50.9% (1307) related to B/Malaysia/2506/2004-like and 49.1% (1263) related to B/Brisbane/60/2008 (included in 2010 Southern Hemisphere seasonal influenza vaccine). The remaining 294 (10.3%) were B/Yamagata viruses related to B/Florida/4/2006-like. 2

Antiviral Resistance

Pandemic (H1N1) 2009

The WHO has reported that 298 oseltamivir resistant pandemic (H1N1) 2009 viruses have been detected and characterised worldwide. All but one of these isolates showed the same H275Y mutation but all were sensitive to zanamivir.1

The WHO Collaborating Centre in Melbourne has reported that from 1 January 2010 to 27 June 2010, no isolates (out of 23 tested) have shown resistance to oseltamivir or zanamivir by enzyme inhibition assay (EIA) and two isolates (out of 5 tested) have shown the H275Y mutation known to confer resistance to oseltamivir.

4. International Influenza Surveillance

WHO Summary as at 25 June 2010

There have been over 18,209 deaths associated with pandemic (H1N1) 2009 worldwide.

Northern Hemisphere

  • Overall pandemic influenza activity remains low worldwide with active transmission in the Caribbean, West Africa, South and Southeast Asia.
  • Circulation of seasonal influenza type B viruses:
    • has declined substantially
    • is occurring at low levels across East Asia, Central Africa and
      Central America.
  • During the past month, seasonal influenza H3N2 viruses have been detected at low levels across parts of East Africa and South America.

Southern Hemisphere

  • Pandemic and seasonal influenza viruses have been detected only sporadically during the early part of winter in the temperate regions.

5. Data considerations

The information in this report is reliant on the surveillance sources available to the Department of Health and Ageing. As access to sources increase and improve, this report will be refined and additional information will be included.

This report aims to increase awareness of pandemic (H1N1) 2009 and seasonal influenza in Australia by providing an analysis of the various surveillance data sources throughout Australia. While every care has been taken in preparing this report, the Commonwealth does not accept liability for any injury or loss or damage arising from the use of, or reliance upon, the content of the report. Delays in the reporting of data may cause data to change retrospectively. For further details about information contained in this report please contact the Influenza Team through flu@health.gov.au.

On 17 June 2009 Australia commenced the transition to a new response phase called PROTECT, in which laboratory testing is directed towards people with moderate or severe illness; those more vulnerable to severe illness; and those in institutional settings. This means that the number of confirmed cases does not reflect how many people in the community have acquired pandemic (H1N1) 2009 infection.

NetEpi

In 2009, NetEpi, a web-based outbreak case reporting system for pandemic (H1N1) 2009, was used as the primary source of enhanced data on confirmed cases, hospitalisations and ICU admissions in all jurisdictions. In 2010, only data for NSW are sourced from NetEpi.

Analyses of Australian cases are based on the diagnosis date, which is the earliest of the onset date, specimen date or notification date.

National Notifiable Diseases Surveillance System (NNDSS)

Laboratory confirmed influenza (all types) is notifiable in all jurisdictions in Australia. Confirmed cases of influenza are notified through NNDSS by all jurisdictions except NSW. NSW data are sourced from NetEpi.

Data Analysis

Analysis of confirmed influenza cases is conducted on combined NetEpi and NNDSS data. Analysis of morbidity (hospitalisations and ICU admissions) and mortality data in 2009 has been conducted on combined NetEpi and QLD hospitalisation data.

Laboratory Surveillance data

Laboratory testing data are extracted from the 'NSW Influenza Report,' and the 'The 2009 Victorian Influenza Vaccine Effectiveness Audit Report' (VIDRL) 'South Australian Seasonal Influenza Report'. These reports are provided weekly.

WHO Collaborating Centre for Reference & Research on Influenza (WHO CC)

Data are provided weekly to the Surveillance Branch from the WHO CC.

Sentinel General Practice Surveillance

The Australian Sentinel Practices Research Network (ASPREN) has Sentinel GPs who report ILI presentation rates in NSW, SA, ACT, VIC, QLD, TAS and WA. As jurisdictions joined ASPREN at different times and the number of GPs reporting has changed over time, the representativeness of ASPREN data in 2009 may be different from that of previous years. ASPREN data and VIDRL influenza surveillance data are sent to the Surveillance Branch on a weekly basis. Further information on Sentinel GPs' Influenza Surveillance and ASPREN activities are available at www.dmac.adelaide.edu.au/aspren.

Sentinel ED data

WA - ED surveillance data are extracted from the 'Virus Watch' Report. This report is provided weekly. The Western Australia Influenza Surveillance Program collects data from eight Perth EDs.
NSW - ED surveillance data are extracted from the 'Influenza Monthly Epidemiology Report, NSW'. This report is provided monthly. The New South Wales Influenza Surveillance Program collects data from 49 EDs across New South Wales.

Absenteeism

A national organisation provides data on the number of employees who have been on sick leave for a continuous period of more than three days. These data are not influenza or ILI specific and absenteeism may be a result of other illnesses.

National Health Call Centre Network

A national organisation provides call centre data for calls relating to ILI or influenza. Data are provided daily and are collated weekly and have been presented in this report to show the pattern of calls to this Call Centre over the 2009 season. Data is available for all jurisdictions other than QLD and VIC.

FluTracking

FluTracking is a project of the University of Newcastle, the Hunter New England Area Health Service and the Hunter Medical Research Institute. FluTracking is an online health surveillance system to detect epidemics of influenza. It involves participants from around Australia completing a simple online weekly survey, which collects data on the rate of ILI symptoms in communities.
Data have been provided weekly and have been presented in this report to show the pattern of self reported ILI in the community over the 2009 season.

Further information on FluTracking is available at www.flutracking.net/index.html.

FluCAN

The Influenza Complications Network (FluCAN) collects detailed clinical information on all hospitalised cases of influenza and pneumonia from a sample of 15 sentinel hospitals across Australia. The data for this reporting period are sourced only from 11 hospitals and do not include NT.

Australian and New Zealand Intensive Care Society data (ANZICS data)

The Australian and New Zealand Intensive Care Society provides data from a 'near real time' registry of patients admitted to Australian ICUs. This documents the key factors influencing mortality, as well as the need for hospitalisation and mechanical ventilation. Information collected includes person characteristics and information on relevant co-morbidities, nature of the clinical syndrome associated with pandemic (H1N1) 2009, major therapeutic interventions from which organ failure outcomes can be imputed, vaccination status and vital status at time of ICU discharge and hospital discharge.

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6. References


1WHO Pandemic (H1N1) 2009 - Update 106 & Virological Surveillance Weekly Update. Available from http://www.who.int/csr/don/en/ Accessed 30 June 2010.
2Chinese National Influenza Centre Influenza Weekly Report 20 June 2010. Available from: http://www.cnic.org.cn/eng/ Accessed 30 June 2010.