Clinical predictors of disease severity during the 2009-2010 A(HIN1) influenza virus pandemic in a paediatric population

Abstract

A novel influenza virus emerged in the United States in spring 2009, rapidly becoming a global pandemic. Children were disproportionally affected by the novel influenza A(H1N1) pandemic virus [A(H1N1)pdm]. This retrospective electronic medical record review study aimed to identify clinical predictors of disease severity of influenza A(HIN1)pdm infection in paediatric patients. Disease severity was defined on an increasing three-level scale from non-hospitalized, hospitalized, and admitted to the intensive care unit (ICU). From April 2009 to June 2010, 696 children presented to Texas Children's Hospital's emergency department, 38% were hospitalized, and 17% were admitted to the ICU. Presenting symptoms associated with severe influenza were dyspnoea [odds ratio (OR) 5·82], tachycardia (OR 2·61) and fatigue (OR 1·96). Pre-existing health conditions associated with disease severity included seizure disorder (OR 4·71), obesity (OR 3·28), lung disease (OR 2·84), premature birth (OR 2·53), haematological disease (OR 2·22), and developmental delay (OR 2·20). According to model fitness tests, presenting symptoms were more likely to predict severe influenza than underlying medical conditions. However, both are important risk factors. Recognition of clinical characteristics associated with severe disease can be used for triaging case management of children during future influenza outbreaks.

Keywords: Disease severity; epidemiology; influenza A; outbreaks; pandemic; risk factors.

Fig. 1.

Epidemic curve of 2009 A(HIN1)pdm influenza cases' date of onset, stratified by hospital admission status, April 2009–June 2010.

Fig. 2.

Count of H1N1 paediatric cases per zip code attending Texas Children's Hospital from April 2009 to June 2010. The bold red cross represents the location of Texas Children's Hospital.

Fig. 3.

Descriptive characteristics of the 2009 A(HIN1)pdm influenza paediatric cases at Texas Children's Hospital by hospital admission status. Texas Children's Health Plan (TCHP) is a type of insurance for children living in Harris County that qualify for Medicaid or Medicare, which allows for Harris County to directly pay providers within the Texas Children's healthcare network (http://www.texaschildrenshealthplan.org).