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

Abstract

Objective: To compare the patient characteristics, clinical features and outcomes of adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal influenza. Design and setting: Retrospective medical record review of all patients admitted to Liverpool Hospital, Sydney, with laboratory‐confirmed influenza from the initiation of the “PROTECT” phase of the pandemic response on 17 June until the end of our study period on 31 July 2009. Main outcome measures: Severity of illness; requirement for admission to the intensive care unit (ICU) and/or invasive ventilation; mortality. Results: Sixty‐four adults were admitted to Liverpool Hospital with influenza, 48 with pandemic (H1N1) 2009 influenza and 16 with seasonal influenza. Thirteen patients were admitted to the ICU. Seven required invasive ventilation, with 2 patients requiring ongoing extracorporeal membrane oxygenation (ECMO). Five patients died (mortality rate, 8%) with two deaths occurring after the study period. Patients with pandemic (H1N1) 2009 influenza were younger and less likely to be immunocompromised than patients with seasonal influenza. However, the clinical features of pandemic (H1N1) 2009 influenza and seasonal influenza were similar. Conclusions: Our findings show that the clinical course and outcomes of pandemic (H1N1) 2009 influenza virus are comparable to those of the current circulating seasonal influenza in Sydney. 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.

Concurrent comparison of epidemiology, clinical presentation and outcome between adult patients suffering from the pandemic influenza A (H1N1) 2009 virus and the seasonal influenza A virus infection

“…In contrast to the study conducted by Chang et al , 9 which is also a concurrent analysis of hospitalised patients with pandemic A (H1N1) and seasonal influenza, our study found several differences in the clinical features of patients with pandemic A (H1N1) and seasonal influenza. This may be because our study included more patients, allowing detection of smaller differences.…”

“…There have been two studies in the southern hemisphere which concurrently compared pandemic A (H1N1) and seasonal influenza. The first study, conducted in Sydney, Australia, found that patients with pandemic A (H1N1) were younger and less likely to be immunocompromised than those with seasonal influenza 9. In that study, there were no statistically significant differences in the clinical features and outcome between pandemic A (H1N1) and seasonal influenza.…”

Characteristics of Outpatients with Pandemic H1N1/09 Influenza in a Tertiary Care University Hospital in Korea

“…These findings differ from those of other studies 9,10. The difference may be attributed, at least in part, to the time of investigation.…”

A Two wave analysis of hospitalizations and mortality from seasonal and pandemic 2009 A (H1N1) influenza in Saurashtra, India: 2009-2011

“…The 4.3% (22/511) patients reported pregnancy [Table 4] in this study among A (H1N1) influenza patients was higher than the expected prevalence in the general population (1%),[28] in contrast, 7% was reported in US,[19] 11% in New Zealand,[23] and 16.7% in Australia. [29] During periods of seasonal influenza and past pandemics, pregnant women have been at higher risk for influenza associated morbidity and mortality. [28293031]…”

“…[29] During periods of seasonal influenza and past pandemics, pregnant women have been at higher risk for influenza associated morbidity and mortality. [28293031]…”