Australian influenza report 2012—29 September to 12 October 2012 (#10/2012)

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. Reports are produced weekly from May to October. A more in-depth end-of-season report is also published in Communicable Diseases Intelligence.

Page last updated: 25 October 2012

Report No. 10
Reporting period: 29 September to 12 October 2012

A print friendly version of this report is available (PDF 2198 KB)

The Department of Health and Ageing (the department) 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 using the following indicators and surveillance systems:
Is the situation changing?Indicated by trends in:
  • laboratory confirmed cases reported to the National Notifiable Diseases Surveillance System (NNDSS)
  • general practitioner (GP) consultations for influenza-like illness (ILI)
  • emergency department (ED) presentations for ILI
  • ILI-related call centre calls and community level surveys of ILI, and
  • sentinel laboratory test results.
How severe is the disease, and is severity changing?Indicated by trends in:
  • hospitalisations, intensive care unit (ICU) admissions and deaths, and
  • clinical severity in hospitalised cases and ICU admissions.
Is the virus changing?Indicated by trends in:
  • drug resistance, and
  • antigenic drift or shift of the circulating viruses.

Summary

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  • Nationally, influenza activity continued to decrease this fortnight.
  • All jurisdictions have reported localised and sporadic influenza activity. Influenza activity was reported as decreasing or stable across all jurisdictions, with the exception of Central Australia.
  • Compared with the previous year, influenza activity during the 2011/12 inter-seasonal period remained relatively low.
  • As at 12 October 2012, there have been 41,981 laboratory confirmed cases of influenza reported. Excluding 2009, notifications of influenza in 2012 started their seasonal increase earlier, rose sharply and peaked higher in comparison with previous years.
  • The majority of jurisdictions peaked in activity around mid-July, however, ongoing increased activity continued to be reported in Queensland until the peak in mid-August.
  • Through 2012 there have been very few notifications of pandemic (H1N1) 2009. Nationally, influenza A(H3N2) was the predominant circulating virus this influenza season, along with increasing co-circulation of influenza B. Influenza B was the predominant circulating virus this reporting period, comprising 53% of notifications.
  • In 2010 and 2011 with the predominance of the pandemic (H1N1) 2009 virus, the age distribution of notifications showed a downward trend with increasing age. With the predominance of influenza A(H3N2) in 2012, the age distribution of notifications are currently reflective of traditional pre-pandemic seasons with peaks among those aged 0-4 and over 70 years.
  • Influenza associated hospitalisations have continued to decrease following a peak in mid-July. Known medical co-morbidities have been reported in 75% of hospitalised cases and the rate of hospitalisations was highest amongst cases aged over 70 years, followed by those aged 0-9 years.
  • The WHO has reported that influenza activity has continued to decline in all temperate countries of the southern hemisphere. Seasonal influenza transmission has not yet been detected in the northern temperate zone.
  • The Australian Influenza Vaccine Committee (AIVC) has agreed to adopt the WHO recommendations for the composition of the 2013 southern hemisphere influenza season vaccine. In comparison to the current 2012 southern hemisphere vaccine, the recommended A(H3N2) and B viruses have been changed in line with the WHO recommended 2012-13 northern hemisphere vaccine.
  • This will be the final Australian Influenza Surveillance Report for 2012, unless unusual activity becomes apparent over the summer months.

  1. Geographic Spread of Influenza Activity in Australia
  2. Influenza-like illness activity
  3. Laboratory confirmed influenza activity
  4. Virological Surveillance
  5. International Influenza Surveillance
  6. Data considerations
  7. References


1. Geographic Spread of Influenza Activity in Australia

In the fortnight ending 12 October 2012, the geographic spread of influenza activity reported by state and territory Health Departments was ‘localised’ in New South Wales, South Australia, Central Australia and WA other. All remaining regions reported sporadic activity (figure 1). Across Australia influenza activity was reported as either decreasing or no change in activity, with the exception of Central Australia which reported increasing activity. During this period all jurisdictions reported no evidence of an increase in ILI via syndromic surveillance systems (with the exception of NSW and the ACT which did not report). Definitions of these activity levels are provided in the Data Considerations section of this report.
Figure 1. Map of influenza activity by state and territory, 29 September to 12 October 2012

Figure 1. Map of influenza activity by state and territory, 29 September to 12 October 2012 - see above for a detailed description
Figure 1 - Legend

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2. Influenza-like illness activity

Community Level Surveillance

FluTracking
FluTracking, a national online system for collecting data on ILI in the community, noted that in the week ending 14 October 2012, fever and cough was reported by 1.8% of vaccinated participants and 1.8% of unvaccinated participants (figure 2)1. Fever, cough and absence from normal duties was reported by 1.1% of vaccinated participants and 1.2% of unvaccinated participants. Rates of ILI among FluTracking participants have been relatively stable over the most recent fortnight and are less than in previous years for the same period (figure 3).

In the week ending 14 October 2012, 54.0% of participants reported having received the seasonal vaccine so far. Of the 2,539 participants who identified as working face-to-face with patients, 73.5% have received the vaccine.
Figure 2. Proportion of cough and fever among Flutracking participants, week ending 6 May 2012 to 14 October 2012, by vaccination status and week

Figure 2. Proportion of cough and fever among Flutracking participants, week ending 6 May 2012 to 14 October 2012, by vaccination status and week - see above for a detailed description

Source:FluTracking1

Figure 3. Proportion of fever and cough among FluTracking participants, between May and October, 2008 to 2012, by week

Figure 3. Proportion of fever and cough among FluTracking participants, between May and October, 2008 to 2012, by week - see above for a detailed description

Source: FluTracking1

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National Health Call Centre Network
In the week ending 14 October 2012, the number of ILI related calls to the National Health Call Centre Network (NHCCN) continued to decrease to 613 calls, representing 4.9% of total calls. This decrease follows a peak of 1,836 ILI related calls (12.7%) in mid-July. The number and proportion of ILI weekly related calls to the NHCCN in 2012 have generally been higher than the peaks experienced in 2010 and 2011 (figure 4).
Figure 4. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 14 October 2012, by week

Figure 4. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 14 October 2012, by week - see above for a detailed description

Note: NHCCN data do not include Queensland and Victoria
Source: NHCCN data

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Sentinel General Practice Surveillance

In the week ending 14 October 2012, the sentinel general practitioner ILI consultation rate fell to 2.2 cases per 1,000 consultations and is well below the peak of 17.8 cases in mid-July (figure 5). Compared with previous years (excluding 2009), there was an earlier increase and a slightly higher peak in ILI consultation rates compared with the seasonal peaks reported in 2010 and 2011. That said, the rate of ILI is now below the usual rate for this time of year.
Figure 5. Weekly rate of ILI reported from GP ILI surveillance systems, 1 January 2008 to 14 October 2012, by week*

Figure 5. Weekly rate of ILI reported from GP ILI surveillance systems, 1 January 2008 to 14 October 2012, by week - see above for a detailed description

* Delays in the reporting of data may cause data to change retrospectively. As data from the previous Northern Territory surveillance system was combined with ASPREN and VIDRL surveillance data for 2008 and 2009, rates may not be directly comparable with 2010-2012.

Source: ASPREN and VIDRL2 GP surveillance system.

In the fortnight ending 14 October 2012, specimens were collected from around half of ASPREN ILI patients. Of these patients, 17% were positive for influenza, down from 18% in the previous fortnight. Almost 7% were positive for influenza type A (with the majority likely to be attributed to A(H3N2)) and 10% were influenza type B (figure 6 and table 1). Around 26% of specimens collected were positive for other respiratory viruses this fortnight, with the majority of these being human metapneumovirus or parainfluenza.
Table 1. ASPREN laboratory respiratory viral test results of ILI consultations, 1 January 2012 to 14 October 2012.
Fortnight
(1 October – 14 October 2012)
YTD
(1 January – 14 October 2012)

Total specimens tested

58
3212

Total Influenza Positive (%)

17.2
39.6

   Influenza A (%)

6.9
27.6

     Pandemic (H1N1) 2009 (%)

0.0
0.5

     Influenza A (unsubtyped) (%) #

6.9
27.1

   Influenza B (%)

10.3
11.9

Other Resp. Viruses (%)*

25.9
19.3

# The majority of type A(unsubtyped) notifications are likely to be attributed to A(H3N2)
* Other respiratory viruses include RSV, parainfluenza, adenovirus and rhinovirus.

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Figure 6. Proportion of respiratory viral tests positive for influenza in ILI patients and GP ILI consultation rate, 1 January 2012 to 14 October 2012, by week

Figure 6. Proportion of respiratory viral tests positive for influenza in ILI patients and GP ILI consultation rate, 1 January 2012 to 14 October 2012, by week - see above for a detailed description

Source: ASPREN and WA SPN


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Sentinel Emergency Department Surveillance

Western Australia Emergency Departments
Respiratory viral presentations to Perth emergency departments have continued to fluctuate at stable levels (figure 7). The proportion of cases admitted increased, however, from 6.7% to 8.0% for the week ending 14 October. Presentations are now within the usual range for this time of year, following an earlier increase and a higher than usual peak in July. Over the fortnight to 14 October there were 944 presentations, including 69 admissions.
Figure 7. Number of respiratory viral presentations to Western Australia emergency departments, 1 January 2008 to 14 October 2012, by week

Figure 7. Number of respiratory viral presentations to Western Australia emergency departments, 1 January 2008 to 14 October 2012, by week - see above for a detailed description

Source: WA 'Virus Watch' Report3.

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New South Wales Emergency Departments
In the week ending 12 October 2012 the number of patients presenting to NSW emergency departments with influenza-like illness was similar to the previous week with 0.7 cases per 1000 presentations. The presentation rate was below the usual range for this time of year and well below the peak of activity seen in mid-July (figure 8). Total admissions from emergency departments to critical care units for ILI and pneumonia increased this week and are slightly above the usual range for this time of year.4
Figure 8. Rate of influenza-like illness presentations to New South Wales emergency departments, between May and October, 2008 to 2012, by week

Figure 8. Rate of influenza-like illness presentations to New South Wales emergency departments, between May and October, 2008 to 2012, by week - see above for a detailed description

Source: NSW Influenza Weekly Epidemiology Report4

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Northern Territory Emergency Departments
In the fortnight ending 13 October 2012, 339 patients presented with ILI to emergency departments across the Northern Territory, compared with 386 in the previous fortnight. The number of presentations to emergency departments in the Northern Territory between May and August 2012 were slightly higher compared with previous years (excluding 2009), however they remain well below the peak reported in 2011 and are now within usual levels for this time of year (figure 9).
Figure 9. Number of ILI presentations to Northern Territory emergency departments, 1 January 2008 to 13 October 2012, by week

Figure 9. Number of ILI presentations to Northern Territory emergency departments, 1 January 2008 to 13 October 2012, by week - see above for a detailed description

Source: Centre for Disease Control, Department of Health, Northern Territory Government

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3. Laboratory Confirmed Influenza Activity

Notifications of Influenza to Health Departments

During the reporting period there were 656 laboratory confirmed influenza notifications reported to the NNDSS, a 59% decrease on notifications reported in the previous fortnight (1,581). Nationally, notifications have continued to decrease (figure 10). Almost 40% of notifications this fortnight were from Queensland (258) where there continues to be a decreasing trend. Notifications reported from all other jurisdictions this fortnight were: Victoria (139), South Australia (96), New South Wales (81), Western Australia (57), the NT (17), ACT (4) and Tasmania (4). A weekly breakdown of trends by state and territory highlights that notifications are decreasing across all jurisdictions (figure 11).
Figure 10. Notifications of laboratory confirmed influenza, Australia, 1 January to 12 October 2012, by state or territory and week

Figure 10. Notifications of laboratory confirmed influenza, Australia, 1 January to 12 October 2012, by state or territory and week - see above for a detailed description

Source: NNDSS

Figure 11. Notifications of laboratory confirmed influenza, 1 January to 12 October 2012, by state or territory and week

Figure 11. Notifications of laboratory confirmed influenza, 1 January to 12 October 2012, by state or territory and week - see above for a detailed description

Source: NNDSS

Top of pageIn 2010 and 2011, with the predominance of the pandemic (H1N1) 2009 virus, the age distribution of influenza notifications showed a downward trend with increasing age. However, in 2012 with the predominance of influenza A(H3N2), the age distribution of influenza notifications has shown a bimodal trend with peaks in those aged under 10 years and in those aged 70 years and over, with a small peak among those aged 30-44 years. This age distribution is more reflective of traditional pre-pandemic seasons (figure 12).
Figure 12. Rates of laboratory confirmed influenza, 1 January 2008 to 12 October 2012, by age group

Figure 12. Rates of laboratory confirmed influenza, 1 January 2008 to 12 October 2012, by age group - see above for a detailed description

Source: NNDSS

Top of pageUp to 12 October, there have been 41,981 laboratory confirmed notifications of influenza diagnosed during 2012 (figure 13). Of these notifications, there have been 16,295 in Queensland, 7,516 in New South Wales, 5,553 in Victoria, 5,482 in South Australia, 5,059 in Western Australia, 1,053 in Tasmania, 631 in the ACT and 392 in the Northern Territory.
Figure 13. Notifications of laboratory confirmed influenza, Australia, 1 January 2008 to 12 October 2012, by week

Figure 13. Notifications of laboratory confirmed influenza, Australia, 1 January 2008 to 12 October 2012, by week - see above for a detailed description

Source: NNDSS

Top of pageOf the 656 influenza notifications reported to the NNDSS this reporting period, 282 were influenza A (252 were influenza A (unsubtyped), 26 were A(H3N2) and 4 were pandemic (H1N1) 2009), 372 were influenza B and 2 notifications were reported as influenza C or untyped (figure 13). The majority of type A (unsubtyped) notifications are likely to be attributed to A(H3N2).

Up to 12 October 2012, 32,662 cases (78%) were reported as influenza A (60% influenza A (unsubtyped), 17% A(H3N2) and 1% pandemic (H1N1) 2009) and 9,096 (22%) were influenza B. A further 46 (<1%) were influenza type A&B, 7 (<1%) were influenza C, and 52 (<1%) were untyped (figure 14).

Nationally, influenza B continues to be the predominant circulating virus during this reporting period. Influenza B currently represents 78% of notifications in New South Wales, 75% in the Australian Capital Territory, 61% in Queensland, 55% in Victoria and 53% in South Australia. Influenza A was the predominant virus over the fortnight to 12 October, however, in Tasmania, Western Australia and the Northern Territory. There have been very few notifications of pandemic (H1N1) 2009 reported since 1 January 2012.
Figure 14. Notifications of laboratory confirmed influenza, Australia, 1 January to 12 October 2012, by sub-type and week

Figure 14. Notifications of laboratory confirmed influenza, Australia, 1 January to 12 October 2012, by sub-type and week - see above for a detailed description

Source: NNDSS

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Sentinel Laboratory Surveillance

Results from sentinel laboratory surveillance systems for this reporting period show that 3.4% of the respiratory viral tests conducted over this period were positive for influenza, a decrease from 8.7% in the previous fortnight (table 2). A breakdown of subtypes within this positive proportion by fortnight is highlighted in figure 15. Human metapneumovirus (HMPV) and rhinovirus were the most common respiratory viruses reported.
Table 2. Sentinel laboratory respiratory virus testing results, 1 September to 12 October 2012
NSW NICWA NICVIC NICTAS
(PCR Testing Data)

Total specimens tested

280
406
176
139

Total Influenza Positive

10
14
7
3

  Positive influenza A

3
8
4
2
        Pandemic (H1N1) 2009
0
0
0
0
        A(H3N2)
3
8
4
0
        A (unsubtyped)
0
0
0
2

  Positive influenza B

7
6
3
1

  Positive influenza A&B

0
0
0
0

Proportion Influenza Positive (%)

3.6%
3.4%
4.0%
2.2%
Most common respiratory virus detected
Rhinovirus
HMPV
Picornavirus and HMPV
Rhinovirus

Source: National Influenza Centres (WA, Vic, NSW) and Tasmanian laboratories (PCR testing)

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Figure 15. Proportion of sentinel laboratory tests positive for influenza, 26 May to 12 October 2012, by subtype and fortnight

Figure 15. Proportion of sentinel laboratory tests positive for influenza, 26 May to 12 October 2012, by subtype and fortnight - see above for a detailed description

Source: National Influenza Centres (WA, Vic, NSW) and Tasmanian laboratories (PCR testing)

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Hospitalisations

Influenza Complications Alert Network (FluCAN)
The Influenza Complications Alert Network (FluCAN) sentinel hospital surveillance system has reported that the number of confirmed influenza hospital admissions continued to decrease over the fortnight to 12 October 2012. Since 7 April 2012, 9% of influenza patients have been admitted directly to ICU. Overall, the majority of admissions have been with influenza A, with 17% of cases due to influenza B (figure 16). Around 46% of the cases are aged 65 years and over (median age 61 years) and 75% of all cases have known medical co-morbidities.
Figure 16. Number of influenza hospitalisations at sentinel hospitals, 7 April to 12 October 2012, by week and influenza subtype

Figure 16. Number of influenza hospitalisations at sentinel hospitals, 7 April to 12 October 2012, by week and influenza subtype - see above for a detailed description

Source: FluCAN Sentinel Hospitals

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Queensland Public Hospital Admissions (EpiLog)
Admissions to public hospitals in Queensland of confirmed influenza are detected through the EpiLog system. Up to 14 October 2012, there have been 1,603 admissions of confirmed influenza this year, including 157 to intensive care units. In the most recent fortnight, hospital admissions have declined to 12 admissions from the peak of 343 admissions in mid-August (figure 17). The age distribution of confirmed influenza admissions in 2012 shows a bimodal distribution with the highest peak in the 70 years and over age group, followed by a secondary peak in the 0-9 year age group.
Figure 17. Number of influenza admissions to Queensland public hospitals, with onset from 1 January to 12 October 2012, by week and type of admission

Figure 17. Number of influenza admissions to Queensland public hospitals, with onset from 1 January to 12 October 2012, by week and type of admission - see above for a detailed description

Source: Queensland Health EpiLog data

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Paediatric Severe complications of influenza
The Australian Paediatric Surveillance Unit conducts seasonal surveillance of children aged 15 years and under who are hospitalised with severe complications of influenza. Between 1 July and 12 October 2012, there have been 48 hospitalisations associated with severe complications of influenza, including 23 ICU admissions. Over 60% of hospitalisations were associated with influenza A infections, with the remaining hospitalisations associated with influenza B. Around one-third of the cases had an underlying chronic condition reported.

Deaths associated with influenza and pneumonia

Nationally Notified Influenza Associated Deaths
So far in 2012, 60 influenza associated deaths have been notified to the NNDSS, with a median age of 78 years. Around 88% of cases were reported as having influenza A(unsubtyped) or A(H3N2), with the A(unsubtyped) infections also likely to be attributable to A(H3N2). The number of influenza associated deaths reported to the NNDSS are reliant on the follow up of cases to determine the outcome of their infection and most likely do not represent the true mortality impact associated with this disease.
New South Wales Influenza and Pneumonia Death Registrations
Death registration data for the week ending 21 September 2012 show that there were 1.45 pneumonia or influenza associated deaths per 100,000 population in NSW, which is below the epidemic threshold of 1.62 per 100,000 NSW population (Figure 18)4. Between 1 July and 21 September 2012, the majority of deaths were in persons aged over 65 years. The rate of deaths classified as influenza and pneumonia was above the epidemic threshold for most of July. The increase in the death rate is consistent with trends observed in laboratory isolations of influenza and emergency department ILI activity, with a delay of one to two weeks.
Figure 18. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 1 January 2007 to 21 September 2012

Figure 18. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 1 January 2007 to 21 September 2012 - see above for a detailed description

Source: NSW 'Influenza Weekly Epidemiology Report'4

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4. Virological Surveillance

Typing and antigenic characterisation

WHO Collaborating Centre for Reference & Research on Influenza (WHO CC), Melbourne
From 1 January to 15 October 2012, there were 1,598 Australian influenza viruses subtyped by the WHO CC with nearly two-thirds being influenza A(H3N2) and a third influenza B. So far this year, very few viruses have been pandemic (H1N1) 2009 (table 3). It is noted that for the Northern Territory these typing data are not reflective of their season, where there was an early predominance of influenza B in the ‘Central’ region, and currently in the ‘Top End’ region there is a predominance of influenza A(H3N2).
Table 3. Australian influenza viruses typed by HI or PCR from the WHO Collaborating Centre, 1 January 2012 to 15 October 2012
Type/Subtype
ACT
NSW
NT*
QLD
SA
TAS
VIC
WA
TOTAL

Pandemic (H1N1) 2009

0
3
1
6
1
0
39
5
56

A(H3N2)

18
217
0
198
101
38
369
67
1008

B

2
50
54
107
56
10
97
158
534

Total

20
270
55
311
158
49
505
230
1598

Source: WHO CC
Note: There may be up to a month delay on reporting of samples.
Viruses tested by the WHO CC are not necessarily a random sample of all those in the community.
*These results do not reflect the current predominance of influenza A(H3N2) in the Top End region of the Northern Territory.

Top of pageThe WHOCC has analysed some of the currently circulating influenza viruses. Whilst almost all of the influenza A(H3N2) viruses are of a more recent strain that differs from the A(H3N2) strain in the 2012 Southern Hemisphere seasonal influenza vaccine, it is expected that the vaccine will still offer significant protection. Additionally there is some co-circulation of the two influenza B lineages. The majority of influenza B viruses are of the B/Victoria lineage (B/Brisbane/60/2008-like) and are similar to the strain in the current vaccine. Some cross-protection against influenza B viruses of the other (B/Yamagata) lineage (B/Wisconsin/1/2010) is expected in adults, though less so for children.

Recent analysis of the B/Brisbane/60/2008-like viruses suggests that around 35% are 'low reactor' compared with the reference virus. As these low reactor viruses do not form a distinct genetic group among the B/Victoria lineage viruses, they are not considered to represent an emerging antigenic drift variant.

Antiviral Resistance

The WHO CC has reported that from 1 January to 15 October 2012, one influenza virus (out of 1314 tested) has shown resistance to the neuraminidase inhibitor oseltamivir. This virus was a pandemic (H1N1) 2009 virus with H275Y mutation in the neuraminidase gene, which is known to confer resistance to oseltamivir.

2013 Southern Hemisphere Vaccine

The Australian Influenza Vaccination Committee (AIVC) met on 3 October 2012 5 and agreed to adopt the WHO recommendations for the composition of the 2013 southern hemisphere influenza season trivalent vaccine. The WHO recommended the following viruses be used:
  • an A/California/7/2009 (H1N1)pdm09-like virus
  • an A/Victoria/361/2011 (H3N2)-like virus, and
  • a B/Wisconsin/1/2010-like virus6.

In comparison to the current 2012 southern hemisphere vaccine, the recommended A(H3N2) and B viruses have been changed in line with the 2012-13 northern hemisphere vaccine.

5. International Influenza Surveillance

The WHO7has reported that as at 12 October 2012, seasonal influenza transmission has not yet been detected in the northern temperate zone. Throughout Europe, 23 countries reported data with activity in all at inter-seasonal levels. In the tropical zone of Central and South America, influenza activity is low. That said, influenza B continues to be commonly detected across Central America. In temperate Asian countries ILI activity continued to remain low with exception of Mongolia (increased ILI and respiratory hospitalisations in the past weeks).

Influenza activity has continued to decline in all temperate countries of the southern hemisphere. In South Africa, influenza virus detections continue to decrease after a peak in late July with currently mainly influenza B virus transmission. After some late influenza activity, Argentina is now reporting a decline in influenza virus detections (influenza A(H1N1)pdm09 and influenza B virus).

In New Zealand8, during September 2012, the national monthly rate of ILI consultations was 27.4 per 100,000. Virological surveillance through both sentinel and non-sentinel laboratories shows that so far this year, to 30 September 2012, 65% have been influenza A(H3N2) viruses, 11% influenza B viruses and 10% were pandemic (H1N1) 2009 virus detections, with the remainder being influenza A (unsubtyped)9.

National Influenza Centres (NICs) and other national influenza laboratories from 88 countries, areas or territories reported that for the period 16 to 29 September 2012, a total of 823 specimens were positive for influenza viruses with 56% being influenza A and 44% were influenza B. Of the sub-typed influenza A viruses, 75% were influenza A(H3N2) and 25% were influenza pandemic (H1N1) 2009. Of the characterized B viruses, 68% belong to the B-Victoria lineage and 32% to the B-Yamagata lineage.10.

Influenza A (H3N2) Variant Viruses—United States of America

Between 12 May to 22 Sep 2012, 306 cases of H3N2v virus were reported across multiple U.S. states, with 16 H3N2v-associated hospitalizations and one H3N2v-associated death11.Direct contact with swine has been reported by the vast majority of cases, and influenza A (H3N2) viruses have been identified from swine that are genetically similar to H3N2v viruses from humans. Suspected human-to-human transmission has been identified in a small number of cases, but ongoing community transmission of this virus has not been detected. Associated illness so far has been mostly mild with symptoms similar to seasonal flu and most cases have occurred in children who have little immunity against this virus.

In addition, over the same period, three cases of influenza A (H1N2) variant (H1N2v) virus infection and one case of influenza A (H1N1) variant (H1N1v) virus were detected during this period as a result of enhanced surveillance activities for H3N2v12. All four patients reported direct exposure to swine in the week before illness onset; one was hospitalized, and all four have recovered.

6. Data considerations

The information in this report is reliant on the surveillance sources available to the department. As access to sources increase as the season progresses, this report will be updated with the additional information.

This report aims to increase awareness of influenza activity 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 theInfluenza Surveillance Team.Top of page

Geographic Spread of Influenza Activity

Influenza Activity Levels
Activity levelLaboratory notificationsInfluenza outbreaks
SporadicSmall number of lab confirmed influenza detections (not above expected background level)+ANDNo outbreaks
LocalisedRecent increase in lab confirmed influenza detections above background level++ in less than 50% of the influenza surveillance regions** within the state or area ORSingle outbreak only
RegionalSignificant*** recent increase in lab confirmed influenza detections above baseline in less than 50% of the influenza surveillance regions within the state or area OR> 1 outbreaks occurring in less than 50% of the influenza surveillance regions within the state or area+++
Widespread Significant recent increase in lab confirmed influenza detections above baseline in equal to or greater than 50% of the influenza surveillance regions within the state or areaOR> 1 outbreaks occurring in equal to or greater than 50% of the influenza surveillance regions within the state or area

+ Small no of lab detections = not above expected background level as defined by state epidemiologists.
++ Increase in lab confirmed influenza detections = above expected threshold as defined by state epidemiologists.
* Influenza surveillance region within the state/area as defined by state epidemiologists.
*** Significant increase is a second threshold to be determined by the state epidemiologists to indicate level is significantly above the expected baseline.
+++ Areas to be subdivision of NT (2 regions), WA (3 regions) and QLD (3 regions) that reflect significant climatic differences within those states resulting in differences in the timing of seasonal influenza activity on a regular basis.
Recent = within the current reporting period.

Syndromic Surveillance Activity
Syndromic surveillance systems*
No evidence of increase in ILI via syndromic surveillance systems
Evidence of increase in ILI via syndromic surveillance systems

* Syndromic surveillance systems = GP sentinel surveillance, ED ILI surveillance, Flu tracking (this may be due to a variety of respiratory viruses so the report could add a note to indicate if other evidence suggests that the increase is suspected to be influenza activity or due to another respiratory pathogen). Syndromic surveillance is reported on a state wide basis only

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. Top of page

Further information on FluTracking is available at FluTracking.

Sentinel General Practice Surveillance

The sentinel general practice ILI surveillance data between 2008 and 2012 consists of two main general practitioner schemes, the Australian Sentinel Practices Research Network (ASPREN) and a Victorian Infectious Disease Reference Laboratory (VIDRL) coordinated sentinel GP ILI surveillance program. Additionally, between 2008 and 2009 a Northern Territory surveillance scheme also operated, however this scheme has since been incorporated in to the ASPREN scheme. The national case definition for ILI is presentation with fever, cough and fatigue.

The ASPREN currently has sentinel GPs who report ILI presentation rates in NSW, NT, SA, ACT, VIC, QLD, TAS and WA. The VIDRL scheme operates in metropolitan and rural general practice sentinel sites throughout Victoria and also incorporates ILI presentation data from the Melbourne Medical Deputising Service. As jurisdictions joined ASPREN at different times and the number of GPs reporting has changed over time, the representativeness of sentinel general practice ILI surveillance data in 2012 may be different from that of previous years.

ASPREN ILI surveillance data are provided to the Department on a weekly basis throughout the year, whereas data from the VIDRL coordinated sentinel GP ILI surveillance program is provided between May and October each year.

Approximately 30% of all ILI patients presenting to ASPREN sentinel GPs are swabbed for laboratory testing. Please note the results of ASPREN ILI laboratory respiratory viral tests now include Western Australia.Top of page

Further information is available at ASPREN and information regarding the VIDRL coordinated sentinel GP ILI surveillance program.

Sentinel Emergency Department Data

  • Western Australia—Emergency Department ILI surveillance data are extracted from the 'Virus Watch' Report. This report is produced weekly. The Western Australia Influenza Surveillance Program collects data from eight Perth emergency departments.
  • New South Wales—Emergency Department ILI surveillance data are extracted from the 'Weekly Influenza Report, NSW'. The New South Wales Influenza Surveillance Program collects data from 56 emergency departments across New South Wales.
  • Northern Territory—this sentinel program collects data from the following hospitals: Royal Darwin, Gove District, Katherine District, Tennant Creek and Alice Springs. The definition of ILI is presentation to ED in the NT with one of the following presentations: febrile illness, cough, respiratory infection, or viral illness.

National Notifiable Diseases Surveillance System (NNDSS)

Laboratory confirmed influenza (all types) is notifiable under public health legislation in all jurisdictions in Australia. Confirmed cases of influenza are notified through the NNDSS by all jurisdictions—see the Australian national notifiable diseases case definitions. Analyses of Australian notifications are based on the diagnosis date, which is the earliest of the onset date, specimen date or notification date.

Sentinel Laboratory Surveillance data

Laboratory testing data are provided weekly directly from PathWest (WA), VIDRL (VIC), ICPMR (NSW), and Tasmanian laboratories reporting PCR results. Additionally, approximately 30% of all ILI patients presenting to ASPREN based sentinel GPs are swabbed for laboratory testing.

Influenza Complications Alert Network (FluCAN)

The Influenza Complications Alert Network (FluCAN) sentinel hospital system monitors influenza hospitalisations at the following sites:
    • Australian Capital Territory—the Canberra Hospital and Calvary Hospital
    • New South Wales—John Hunter Hospital and Westmead Hospital
    • Northern Territory—Alice Springs Hospital
    • Queensland—the Mater Hospital, Princess Alexandria Hospital and Cairns Base Hospital
    • South Australia—Royal Adelaide Hospital
    • Tasmania—Royal Hobart Hospital
    • Victoria—Geelong Hospital, Royal Melbourne Hospital, Monash Medical Centre and Alfred Hospital
    • Western Australia—Royal Perth Hospital.
Influenza counts are based on active surveillance at each site for admissions with PCR-confirmed influenza in adults. Some adjustments may be made in previous periods as test results become available. ICU status is as determined at the time of admission and does not include patients subsequently transferred to ICU.

Queensland Public Hospital Admissions (EpiLog)

EpiLog is a web based application developed by Queensland Health. This surveillance system generates admission records for confirmed influenza cases through interfaces with the inpatient information and public laboratory databases. Records are also able to be generated manually. Admissions data reported are based on date of reported onset.

Deaths associated with influenza and pneumonia

Nationally reported influenza associated deaths are notified by jurisdictions to the NNDSS, which is maintained by the department. Notifications of influenza associated deaths are likely to underestimate the true number of influenza associated deaths occurring in the community.

NSW influenza and pneumonia deaths data are collected from the NSW Registry of Births, Deaths and Marriages. Figure 16 is extracted from the 'Weekly Influenza Report, NSW'. NSW Registered Death Certificates are routinely reviewed for deaths attributed to pneumonia or influenza. While pneumonia has many causes, a well-known indicator of seasonal and pandemic influenza activity is an increase in the number of death certificates that mention pneumonia or influenza as a cause of death. The predicted seasonal baseline estimates the predicted rate of influenza or pneumonia deaths in the absence of influenza epidemics. If deaths exceed the epidemic threshold, then it may be an indication that influenza is beginning to circulate widely.

WHO Collaborating Centre for Reference & Research on Influenza

Data on Australian influenza viruses are provided weekly to the Department from the WHO Collaborating Centre for Reference & Research on Influenza based in Melbourne, Australia.

7. References

Top of page1FluTracking, Weekly Interim Report, Week #24 ending 14 October 2012.
2 Victorian Infectious Disease Reference Laboratory, The 2012 Victorian Influenza Vaccine Effectiveness Audit Report, Report 24, Week Ending 14 October 2012.
3 Western Australia Health, Virus WAtch, Week Ending 14 October 2012.
4 NSW Health, Influenza Weekly Epidemiology Report, 6 to 12 October 2012.
5 Australian Influenza Vaccine Committee (AIVC) recommendations for the composition of influenza vaccine for Australia in 2013. Accessed 12 October 2011.
6 WHO, Recommended composition of influenza virus vaccines for use in the 2013 southern hemisphere influenza season. [Accessed 20 September 2012].
7 WHO, Influenza Update No. 170, 12 October 2012. [Accessed 19 October 2012]
8 New Zealand Influenza Monthly Summary – September 2012. [Accessed 19 0ctober 2012].
9 New Zealand Influenza Weekly Update, 24 to 30 September 2012. [Accessed 19 October 2012]
10 WHO, Influenza virus activity in the world, 12 October 2012. [Accessed 19 October 2012]
11 Centres for Disease Control - Influenza A (H3N2) Variant Virus Outbreaks, 5 October 2012. [Accessed 19 October 2012]
12 United States Centres for Disease Control and prevention (CDC), 2012-2013 Influenza Season Week 41 ending October 13, 2012 [Accessed 19 October 2012].