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Health professionals are warning whanau, parents and caregivers not to drop their guard against influenza despite figures showing that the 2013 NZ winter flu season was one of the mildest recorded for more than 20 years.

Surveillance figures by the Southern Hemisphere Influenza Vaccine Effectiveness Research and Surveillance (SHIVERS) Project recorded that the influenza hospitalisation rate of 22.6 per 100 000 during 29th April to 29th September 2013 was lower than that the 34.4 per 100 000 recorded during the same period in 2012.

The proportion of total hospital deaths caused by severe acute respiratory infections also fell from 27.3 per 1000 deaths in 2012 to 13 per 1000 deaths in 2013.

Despite the lower rates SHIVERS Principal Investigator Dr Sue Huang from ESR says the flu still poses a very real health risk, especially to those from Pacific and low socio-economic communities and those under four or over 65 years old.

"Everyone needs to pay close attention to warning signs and not treat every onset of sickness the same. People need medical advice if they are suddenly taken ill with symptoms that include a high temperature (over 38 degrees) and coughing," Dr Huang says.

This year’s SHIVERS study was expanded to capture data from patients visiting their GP in Auckland.

Associate Professor Nikki Turner, Director of the Immunisation Advisory Centre (IMAC) at the University of Auckland and co-lead of the SHIVERS project, says the inclusion of general practice data in this year’s study has provided a more complete picture of flu.

"It’s alerted us to what’s happening in the community as well as in hospitals.

"School aged children are particularly vulnerable to getting the flu, and because of the many circles they tend to move in, are also highly likely to pass it on to others in home and community," Dr Turner says.

The SHIVERS team expects this year’s results to give them a better understanding of the ‘pyramid’ of the disease from mild to severe illness, ICU admissions and deaths in the population, along with the impact on vulnerable subgroups.

"SHIVERS produces the kind of information we need to stay on top of response measures and also helps our colleagues in the Northern Hemisphere better prepare for their flu seasons," Dr Huang says.

This year’s SHIVERS results will be presented to sponsors and partners at a Science Meeting at the University of Auckland’s Tamaki Innovation Campus between 18 and 20 November.

SHIVERS 2013 Media backgrounder
  • Acute respiratory disease led to roughly 71 000 New Zealanders to visit their General Practice, 7 000 hospitalised, 226 admitted in ICU and 21 died.
  • Non-influenza respiratory viruses (RSV, Rhinovirus, Parainfluenza types 1-3, human metapenumovirus, adenovirus) associated respiratory disease led roughly 21 000 New Zealanders to visit their general practice, 3000 hospitalised, 98 admitted to ICU and 9 died.
  • Over a 4 month period of 29th April to 29th September 2013, there were 59688 acute admissions to ADHB and CMDHB hospitals.
  • A total of 3537 patients with suspected respiratory infections were assessed in these hospitals. Of these, 1642 (46.2%) patients met the case definition of a severe acute respiratory illness and were screened for influenza.
  • Among them, 1261 (76.8%) had laboratory testing for influenza, of which 215 (17.1%) had influenza viruses detected, including 71 of influenza B and 145 of influenza A (103 of A(H3N2), 14 of A(H1N1)pdm09 and 28 A not subtyped).
  • A total of 18 sentinel general practices (covering 103,752 enrolled patients) in ADHB and CMDHB participated in community based surveillance for the SHIVERS project. Of 2016 influenza like illness patients consulted their general practices on, 448 influenza viruses were detected.
  • Very young (0-4 years) and elderly (65+ years) had the highest influenza associated hospitalisation rates. However, influenza associated community consultation rates showed a different pattern – high GP consultations in school-aged children and preschoolers and adults.  
  • This indicates that when infants, pre-schoolers and elderly were infected with the influenza virus, they were more likely to progress to the severe end of disease than other age groups. This may be a result of multifactorial influences such as influenza virus pathogenesis, host immune response and socio-demographic factors and health seeking behaviour among these risk age groups.
  • Pacific Peoples had the highest hospitalisation rate of 50.6 per 100 000. This was followed by Maori (26.8 per 100 000), European or others (17.3 per 100 000) and Asian (10.5 per 100 000).
  • However, Asian had the highest community consultation rate (573.2 per 100 000) followed by European or others (405.9 per 100 000), Pacific Peoples (286.1 per 100 000) and Maori (98.4 per 100 000).
  • Lower socio-economic status patients were overly represented. The highest influenza associated hospitalisation rate occurred in the most deprived population. However, influenza associated GP consultations showed an opposite pattern. This may suggest that when the most deprived population were infected with influenza virus, they were more likely to progress to the severe end of disease than other socio-economic groups.
  • SHIVERS data contributed to getting free influenza vaccine to young children in NZ with significant respiratory illness and helping finalise the World Health Organisation’s SARI case definition for "global influenza surveillance standards".
  • The SHIVERS project is a multi-centre and multi-disciplinary collaboration between ESR, Auckland District Health Board, Counties Manukau District Health Board, University of Otago, University of Auckland, the US Centres for Disease Control and Prevention and WHO Collaborating Centre at St Jude Children’s Hospital in Memphis, USA.
  • SARI surveillance is intended to operate for 5 years (2012-2016) with funding from the US Department of Health and Human Services, Centers for Disease Control and Prevention (CDC).

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