Australian influenza report 2010 - 27 March to 3 April 2010 (#13/10)

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: 12 April 2010

Report No. 13
Week ending 4 April 2010

A print friendly version of this report is available as a PDF (210 KB)

Key Indicators

The counting of every case of pandemic influenza is no longer feasible in the PROTECT phase. Influenza activity and severity in the community is instead monitored by the surveillance systems listed below.

Is the situation changing?

Indicated by laboratory confirmed cases reported to NetEpi and/or National Notifiable Diseases Surveillance System (NNDSS); GP Sentinel influenza-like illness (ILI) Surveillance; and emergency department (ED) presentations of ILI at sentinel hospitals (New South Wales and Western Australia).

Laboratory data are used to determine the proportion of pandemic (H1N1) 2009 influenza circulating in the community.
How severe is the disease, and is severity changing?
Indicated by number of hospitalisations, ICU admissions and deaths from sentinel hospital surveillance as well as emergence of more severe clinical picture in hospitalised cases and ICU admissions.
Is the virus changing?
Indicated by emergence of drug resistance or gene drift or shift from laboratory surveillance.


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Summary

  • In 2010, as at 2 April, there have been 57 confirmed cases of pandemic (H1N1) 2009 influenza reported in Australia, bringing the total of confirmed cases to 37,693 since May 2009. In addition, there have been 233 reported cases of influenza type A not sub-typed and 35 cases of influenza type B.
  • From 1 January to 30 March 2010, there have been 14 hospitalisations and 0 deaths associated with pandemic (H1N1) 2009 influenza, as reported by jurisdictions.
  • While there is influenza-like illness (ILI) in the community, levels remain relatively low and reporting from laboratories indicates that little of this ILI is due to influenza. NSW have reported that respiratory syncytial virus (RSV) was the most common respiratory virus diagnosed by sentinel laboratories in March 2010.
  • Pandemic influenza is the predominant influenza strain worldwide, but seasonal influenza B viruses are predominant in East Asia, and low levels have been increasingly detected across western Asia, East Africa, and in parts of eastern and northern Europe.
  • Some South Eastern states of the US continue to experience increased and sustained pandemic flu activity. Georgia has reported a sharp increase in influenza-related hospitalisations.
  • From 1 September 2009 to 28 March 2010, in China, 92.5% of antigenically characterised influenza B viruses were B/Victoria and 7.5% were B/Yamagata viruses. Of the B/Victoria viruses, 47.1% were related to B/Brisbane/60/2008, which is included in the 2010 Southern Hemisphere seasonal influenza vaccine, and 52.9% were related to B/Malaysia/2506/2004-like.
  • As at 28 March 2010, the WHO Regional Offices reported at least 17,483 deaths associated with pandemic (H1N1) 2009 influenza worldwide. In the Northern Hemisphere the areas of highest transmission are the tropical zones of Asia, the Americas and Africa.
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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. There was one new laboratory confirmed pandemic (H1N1) 2009 notification diagnosed this reporting period, in South Australia. In the same period, there were 8 cases of influenza A not sub-typed and 2 cases of influenza B, all in Queensland. (Figures 1 and 2).

There have been 37,693 confirmed cases of pandemic (H1N1) 2009 in Australia as at 2 April 2010, including 191 pandemic influenza-associated deaths. Of these, 37,636 cases were reported in 2009 and 57 cases were reported in 2010 .a

Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 and total influenza in Australia, to 2 April 2010

Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 and total influenza in Australia, to 2 April 2010

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



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

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

Source: NNDSS and NetEpi (NSW).


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Influenza-Like Illness

Sentinel General Practice Surveillance

Combined data available from the Australian Sentinel Practices Research Network (ASPREN) and the Northern Territory GP surveillance system up until 28 March 2010 show that nationally, ILI consultation rates are low and are consistent with levels seen in 2008 and 2009.

In the last week, the presentation rate to sentinel GPs in Australia was approximately 5 cases per 1,000 consultations (Figure 3).

Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2007 to 28 March 2010*

Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2007 to 28 March 2010

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


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WA emergency departments

The number of ILI presentations reported in Western Australian EDs remained stable in the week ending 28 March 2010. Levels are above those seen at the same time in 2007 and 2009, however, were similar to levels seen in 2008 (Figure 4).

Figure 4. Number of Emergency Department presentations due to ILI in Western Australia from 1 January 2007 to 28 March 2010 by week

Figure 4. Number of Emergency Department presentations due to ILI in Western Australia from 1 January 2007 to 28 March 2010 by week

Source: WA ‘Virus Watch’ Report


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NSW emergency departments

In March 2010, there were 90 presentations with influenza–like illness to New South Wales EDs. This is similar to the previous month (88 presentations), but greater than the count of 49 for the month of March 2009.

There were five admissions to hospital following presentation to emergency departments with influenza-like illness in March 2010, compared with four in February 2010 and one in March 2009.

Source: NSW Health ‘Influenza Monthly Epidemiology Report1


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Flutracking

Flutracking, a national online system for collecting data on ILI in the community, reported that in the week ending 4 April 2010 influenza-like illness levels have remained low (Figure 5).

Figure 5. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week (from 3 May 2009 to week ending 4 April 2010)

Figure 5. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week (from 3 May 2009 to week ending 4 April 2010)

Source: Flutracking Interim Weekly Report



National Health Call Centre Network

The number of ILI-related calls received by the NHCCN increased in the week ending 2 April 2010 with 42 calls, compared with 30 calls in the previous reporting period. The number of calls is currently at baseline levels (Figure 6).

Figure 6. Number of calls to the NHCCN related to ILI, Australia, 1 January 2009 to 2 April 2010

Figure 6. Number of calls to the NHCCN related to ILI, Australia, 1 January 2009 to 2 April 2010

Source: NHCCN data


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Deaths associated with influenza and pneumonia

Death registration data show that as at 12 March 2010, there were 69 pneumonia or influenza deaths per 1,000 deaths in NSW, which is below the seasonal threshold of 99 per 1,000 (Figure 7).

Figure 7. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2005 – 2010

Figure 7. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2005 – 2010

Source: NSW ‘Influenza Monthly Epidemiology Report’


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Absenteeism

The most recent data indicate that in the week ending 17 March 2010, national absenteeism rates remained stable and were slightly above levels seen at the beginning of previous years (Figure 8).

Figure 8. Rates of absenteeism (greater than 3 days absent), national employer, from 28 January 2007 to 24 March 2010, by week.

Figure 8. Rates of absenteeism (greater than 3 days absent), national employer, from 28 January 2007 to 24 March 2010, by week

Source: Absenteeism data


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Sentinel Laboratory Surveillance - confirmed influenza notifications

Results from sentinel laboratory surveillance systems for this reporting period show that only two of the respiratory tests conducted over this period were positive for influenza, neither of which were typed (Table 1).

Table 1. Laboratory respiratory tests that tested positive for influenza

  ASPREN* – national NSW NIC WA NIC NT (reported by WA NIC)
Number of specimens tested
3
74
70
N/A
Number tested which were Influenza A
0
2
0
0
Number tested which were pandemic     (H1N1) 2009
0
0
0
0
Number tested which were seasonal   A/H1N1
0
0
0
0
Number tested which were A/H3N2
0
0
0
0
Number tested which were Influenza A untyped
0
2
0
0
Number tested which were Influenza B
0
0
0
0

*ASPREN tests are collected every Tuesday. Results are reported for a rolling fortnight as data changes retrospectively.



Respiratory syncytial virus was the most common respiratory virus diagnosed by NSW sentinel laboratories in March 2010.1
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2. Overview of pandemic (H1N1) 2009 severity - to 2 April 2010b

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

b Note 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.


From 1 January to 30 March 2010, there have been 14 hospitalisations associated with pandemic (H1N1) 2009 influenza, as reported by jurisdictions.

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.

Table 2. Summary of severity indicators of pandemic (H1N1) in Australia, 2009 and 2010 up to 2 April 2010

2009#  2010a
  Confirmed pandemic
(H1N1) 2009 cases
Hospitalised cases ICU cases Deaths Confirmed (H1N1) 2009 cases
Total number
37,636
13% (4,992/37,636) confirmed cases)
14%
(681/4,992 hospitalisations)
191
57
Crude rate per 100,000 population
172.1
22.8
3.1
0.9
0.3
Median age (years)
21
31
44^
53^
28
Females
51% (19,139/37,636)
51% (2,528/4,992)
53%
(364/681)
44%
40%
(23/57)
Vulnerable groups (Indigenous persons, pregnant women & individuals with at least 1 co-morbidity)
n/a
58% (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%
2%
(1/57)
Pregnant women*
n/a
27%
(287/1,056 hospitalised females aged
15-44 years)
16%
(47/289) hospitalised pregnant women)
4%
n/a
Cases with at least 1 co-morbidity
n/a
46% (2,303/4,992)
67%
(457/681)
62%
n/a

a Data 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.
* 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.
** Continuous improvements in the quality of data and small numbers have also resulted in fluctuating in percentages.



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3. Virology

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

From 1 January 2010 to 4 April 2010, there were 21 Australian influenza isolates subtyped by the WHO CC (Table 3). Twenty were Pandemic (H1N1) 2009 and one was Type B.

Table 3. Typing of influenza isolates from the WHO Collaborating Centre, from 1 January 2010 to 4 April 2010

Type/Subtype
ACT NSW NT Qld SA Tas Vic WA TOTAL
A(H1N1)
0
0
0
0
0
0
0
0
0
Pandemic (H1N1) 2009
1
0
3
7
0
1
6
2
20
A(H3N2)
0
0
0
0
0
0
0
0
0
B
0
0
0
0
0
0
1
0
1
Total
1
0
3
7
0
1
7
2
21

Source: WHO CC
Please note: There may be up to a months 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.



Of the 21 influenza isolates subtyped, 2 have been antigenically characterized, and confirmed as pandemic A/H1N1 2009 (A/California/7/2009-like).
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International Updates

The Global Influenza Surveillance Network (GISN) continues to monitor the global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect, humans. Since the beginning of the pandemic on 19 April 2009 to 28 March February 2010, 154 countries shared a total of 24,703 specimens (18,877 clinical samples and 5,826 virus isolates) with WHO Collaborating Centres for further characterisation.2

Pandemic (H1N1) 2009 influenza virus continues to be the predominant influenza virus circulating worldwide. Influenza B viruses are predominant in East Asia, and low levels have been increasingly detected across western Asia, East Africa, and in parts of eastern and northern Europe.

From 1 September 2009 to 28 March 2010, in China, 2214 influenza B viruses have been antigenically characterised. Of those, 2049 (92.5%) are B/Victoria viruses; 52.9% (1083) related to B/Malaysia/2506/2004-like and 47.1% (966) related to B/Brisbane/60/2008 (included in 2010 Southern Hemisphere seasonal influenza vaccine). Of the samples, 165 (7.5%) were B/Yamagata viruses related to B/Florida/4/2006-like.3
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Antiviral Resistance

Pandemic (H1N1) 2009

WHO has reported that 268 oseltamivir resistant pandemic (H1N1) 2009 viruses had been detected and characterised worldwide. All of these isolates showed the same H275Y mutation but were sensitive to zanamivir.

The WHO CC in Melbourne has reported that from 1 January 2010 to 4 April 2010, no isolates have shown resistance to oseltamivir by enzyme inhibition assay (EIA) and two clinical specimens collected in Australia have shown the H275Y mutation known to confer resistance to oseltamivir (Table 4).

Table 4. Neuraminidase resistance testing of Australian pandemic (H1N1) 2009 influenza viruses

  2009 2010
  Viral isolates Clinical specimens Viral isolates Clinical specimens
No. tested
587
276
2
3
EIA Resistant
4
N/A
0
N/A
H275Y mutation
N/A
9
N/A
2

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Seasonal Influenza

The last WHO report on resistance of seasonal influenza strains to oseltamivir was released on 4 June 2009, during the Northern Hemisphere influenza season 2008-2009 and stated that 96% of seasonal influenza A (H1N1) isolates tested from 36 countries worldwide were resistant to oseltamivir.4 Australian oseltamivir resistance testing data on seasonal influenza strains are shown in Table 5.

Table 5. Resistance Testing – Seasonal Influenza – Australia 1 January 2009 to 4 April 2010

% of H1N1 viruses % of A(H3N2) % of B viruses
92.6% (38/41) resistant to oseltamivir
0% (0/54) resistant to oseltamivir
0% (0/6) resistant to oseltamivir

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4. International Influenza Surveillance

WHO Summary as at 26 March 2010

  • There have been 17,483 deaths associated with pandemic (H1N1) 2009 worldwide.
  • Northern Hemisphere
    • The most active areas of pandemic influenza virus transmission are parts of the tropical zones of Asia, the Americas and Africa.
    • Pandemic influenza is the predominant strain worldwide, but seasonal influenza B viruses are predominant in East Asia, and have been increasingly detected at low levels across south east and western Asia, East Africa and in parts of eastern and northern Europe.
    • Seasonal influenza A (H3N2) is still being detected in very small numbers in parts of Asia.
    • Some South Eastern states of the US are experiencing increased and sustained pandemic flu activity. Louisiana and surrounding states reporting an increase in ILI consultation rates and Georgia reported a sharp increase in influenza-related hospitalisations.5
  • Southern Hemisphere
    • Low influenza activity, with sporadic detections of pandemic and seasonal influenza viruses.

Recent influenza activity in selected areas of the Northern and Southern Hemispheres is shown in Table 6.

Table 6. International influenza surveillance by country/region for the most recent reporting week

Country/region End date of most recent reporting week in 2010 Overall influenza activity level Proportion of GP visits that were for ILI Proportion of
Respiratory tests positive for Influenza Influenza which was influenza A Influenza A which was Pandemic (H1N1) 2009 Influenza
A which was
untyped
Northern Hemisphere
USA6
27 March
Low
1.6%
3.5%
100.0%
60.8%
38.1%
Canada7
27 March
Low
2.1%
0.3%
85.7%
50.0%
43.0%
Europe8
28 March
Low
Not reported
8.2%
74.2%
69.6%
20.4%
UK9
1 April
Low
≤0.03%
0.0%
N/A
N/A
N/A
China3
28 March
Not reported
3.5% - 4.0%
23.3%
6.8%
37.3%
0.0%
Southern Hemisphere*
NZ10
28 March
Low
0.01%
0.0%
N/A
N/A
N/A
Chile11
26 January
Low
Not reported
1.4%
0%
N/A
N/A
Argentina11
26 February
Low
<0.01%
Not reported
Not reported
Not reported
Not
reported
Australia
2 April
Low
0.5%
1.4%*
81.8%**
11.1%**
88.9%**

*Source: Sentinel Laboratory Surveillance (see Table 1)
**Source: NNDSS (see Figure 2)


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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

All jurisdictions except QLD are reporting pandemic (H1N1) 2009 cases using NetEpi, a web-based outbreak case reporting system. Data from jurisdictional systems are being imported into NetEpi by VIC, NSW, WA, TAS and SA, and the remainder are entering directly into NetEpi. QLD ceased reporting hospitalisations into NetEpi on 6 July 2009.

Analyses of Australian cases are based on clinical onset date, if this information is available. Where an onset date is not available, notification date has been used. Victoria uses a calculated onset date which is the earliest available date calculated from specimen date, onset date, notification date or detection date. This assumption was made for all calculations and data on which the figures are based.

National Notifiable Diseases Surveillance System (NNDSS)

NNDSS comprises of notifications from jurisdictions of laboratory-confirmed influenza cases. Laboratory confirmed influenza is notifiable in all jurisdictions in Australia. Confirmed pandemic (H1N1) 2009 cases are being received from all jurisdictions through NNDSS except for Victoria and New South Wales. NSW is also unable to send seasonal influenza notifications data.

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 is 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.
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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 influenza-like-illness (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 are sent to the Surveillance Branch on a weekly basis. Northern Territory GP surveillance data are sent to the Surveillance Branch on a weekly basis. 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 Emergency Department (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 8 Perth Emergency Departments (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.

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
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6. References


1. NSW Influenza Monthly Epidemiology Report. Available from http://www.health.nsw.gov.au/publichealth/infectious/index.asp Accessed 7 April 2010.
2. WHO Pandemic (H1N1) 2009 - Update 94 & Virological Surveillance Weekly Update. Available from: http://www.who.int/csr/don/en/ Accessed 7 April 2010.
3. Chinese National Influenza Centre Influenza Weekly Report 28 March 2010. Available from: http://www.cnic.org.cn/eng/ Accessed 7 April 2010.
4. WHO Influenza A virus resistance to oseltamivir and other antiviral medicines, 4 June 2009. Available from: http://www.who.int/csr/disease/influenza/2008-9nhemisummaryreport/en/index.html Accessed 10 March 2010
5. CDC 2009 H1N1 Flu Media Briefing, 29 March 2010. Available from: http://www.cdc.gov/media/transcripts/2010/t100329.htm Accessed 7 April 2010.
6. CDC FluView Weekly report, Week 12 ending 27 March 2010. Available from: http://www.cdc.gov/flu/weekly/ Accessed 7 April 2010.
7. Canada FluWatch Weekly report, week 12 ending 27 March 2010. Available from: http://www.phac-aspc.gc.ca/fluwatch/09-10/index-eng.php Accessed 7 April 2010.
8. ECDC pandemic update, week 12 ending 28 March 2010. Available from: http://ecdc.europa.eu/en/activities/surveillance/EISN/Pages/EISN_Bulletin.aspx Accessed 7 April 2010.
9. HPA weekly pandemic flu media update. Week 13, ending 1 April 2010. Available from: http://www.hpa.org.uk/web/HPAweb&Page&HPAwebAutoListName/Page/1243928258560 Accessed 7 April 2010.
10. New Zealand Ministry of Health Influenza Weekly Update. Week 11, ending 21 March 2010. Available from: http://www.surv.esr.cri.nz/virology/influenza_weekly_update.php Accessed 7 April 2010.
11. Chile Ministry of Health, Influenza A(H1N1) Weekly Report as at 26 January 2010. Available at http://www.redsalud.gov.cl/portal/url/page/minsalcl/g_varios/influenza.html Accessed 7 April 2010.
12. Argentina Ministry of Health, Pandemic Situational Report 26 February 2010. Available from:
http://www.msal.gov.ar/htm/site/default.asp Accessed 7 April 2010.