Letters
Respiratory disease
Volume 192 - Issue 6

Comparison of adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal influenza during the "PROTECT" phase of the pandemic response

Authors:  Andrew R Davies, Steven A Webb, Ian M Seppelt and Rinaldo Bellomo

Med J Aust 2010; 192 (6): 356-358. || doi: 10.5694/j.1326-5377.2010.tb03545.x
Published online: 15 March 2010
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To the Editor: The recent article by Chang and colleagues concluded that “the clinical course and outcomes of pandemic (H1N1) 2009 influenza virus are comparable to those of the current circulating seasonal influenza”, and that: “The high number of hospital admissions reflects a high incidence of disease in the community rather than an enhanced virulence of the novel pandemic influenza virus”.1 We are concerned that these assertions underemphasise the true severity of the influenza pandemic, and have led to inappropriate reporting in the media.2

The single-centre series reported by Chang et al had a small sample size and was almost certainly underpowered to detect important differences. It is also likely that some of the five untypeable patients who were categorised in the seasonal influenza group had had false-negative test results for pandemic (H1N1) 2009 influenza. Despite the small numbers, this study suggested that patients with pandemic (H1N1) 2009 influenza were younger and less immunocompromised than those with seasonal influenza; both of these characteristics of the patients affected may indicate that the pandemic virus is a more virulent strain.

However, regardless of whether its virulence was greater, our significant concern is that our community will underestimate the real burden of the pandemic, which was substantial in Australia and New Zealand during the recent winter. In recent publications, we described more than 700 people admitted to intensive care units (ICUs) throughout these two countries with pandemic (H1N1) 2009 influenza.3,4 These were often young and previously healthy people, and many were pregnant women.3 Two-thirds needed mechanical ventilation for influenza-induced respiratory failure,3 and a smaller but substantial number developed rapidly progressive acute respiratory distress syndrome and required extracorporeal membrane oxygenation (ECMO),4 the most extreme life support available. This is not the normal pattern of influenza in Australasia. In comparison to a normal winter, ICU admissions for viral pneumonitis increased 15-fold,3 and the use of ECMO for acute lung injury increased 17-fold.4 Patients infected with pandemic (H1N1) 2009 influenza required prolonged stays in both the ICU and hospital and, despite optimal care, more than 100 died. ICU bed occupancy by patients with pandemic (H1N1) 2009 influenza ran as high as 19%3 in a system that normally runs close to maximal occupancy. There is a real risk that the pandemic will affect Australia again next winter or earlier, and we feel the Australasian medical community should not be misled into believing that the pandemic (H1N1) 2009 influenza virus is not virulent and has not been responsible for significant mortality and morbidity in a population not normally affected.

Authors

  • Andrew R Davies1
  • Steven A Webb2
  • Ian M Seppelt3
  • Rinaldo Bellomo4
  • 1. Alfred Hospital, Melbourne, VIC.
  • 2. Royal Perth Hospital, Perth, WA.
  • 3. Nepean Hospital, Sydney, NSW.
  • 4. Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, VIC.

Correspondence: a.davies@alfred.org.au

References

View this article on Wiley Online Library

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