Sickle Cell Disease and 2009 Pandemic H1N1 Influenza in Children

Background: Limited data are available on disease characteristics, risk factors and outcomes for children with 2009 pandemic influenza A (H1N1) infection who required hospital admission.

Objective: To ascertain the incidence, baseline characteristics and outcomes of patients with 2009 H1N1 infection.

Methods: This is a retrospective cohort of children ≤18 years old admitted to two hospitals within the Montefiore Medical Center: Moses and Weiler Hospital (Bronx, NY) with influenza-like illness (ILI).  ILI was defined as temperature ≥100.4F with appropriate clinical symptoms.   All patients with ILI were subjected to Luminex xTAG respiratory virus panel (RVP) assay for the detection of seasonal influenza, novel H1N1 and other respiratory viruses.  Univariate and multivariate analysis with logistic regression was performed using STATA version 10.0.

Results: Between October 17, 2009 and December 31, 2009, a total of 594 patients were admitted to the hospital with ILI and 52 (8.8%) were diagnosed with 2009 H1N1 infection.  Among these patients, 14 (26.9%) patients had sickle cell disease (SCD), 21 (40.4%) had asthma and 12 (23.1%) had no past medical history.  The major presenting symptoms were fever (98.1%), cough (92.3%), nasal congestion (76.9%), vomiting (53.9%) and shortness of breath (44.2%).  Six (11.5%) patients had coinfection with other viruses.  Four (7.7%) required intensive care management and all patients survived in this cohort.  There was a 3.4 fold greater risk of H1N1 infection among patients with SCD than those who were SCD negative (p<0.001).  SCD patients were older (p=0.002), more frequently of African American race (p=0.038), presented with a higher incidence of sore throat (p=0.048) and chest pain (p=0.020).  They had shorter onset of symptoms (p=0.001), lower oxygen saturation on arrival (p=0.043), higher WBC (p=0.006), lower hemoglobin (p<0.001) and higher platelet count (p=0.038).  In a multivariate analysis, patients with SCD and H1N1 infection were associated with older age (OR 1.21 [95% CI 1.03 – 1.41]), shorter duration of onset of symptoms (OR 0.44 [95% CI 0.20 – 0.96]) and lower oxygen saturation on presentation (OR 0.75 [95% CI 0.59 – 0.97]).  Comparing SCD patients with ILI and with H1N1 infection to patients with ILI without H1N1 infection, patients with H1N1 infection had higher temperature and lower oxygen saturation on presentation (p=0.001, 0.005 respectively), lower WBC (p=0.107), lower hematocrit (p=0.003) and higher total bilirubin (p=0.017).  Lower WBC (OR 0.77 [95% CI 0.62 – 0.96]), temp ≥102F on admission (OR 27.24 [95% CI 1.82 – 406.07]) and total bilirubin (OR 2.12 [95% CI 1.13 – 3.96]) were independent factors associated with H1N1 infection in the SCD population.

Conclusions: In our cohort, SCD appears to be a significant risk factor for hospitalization with H1N1 infection, and this finding should influence future strategies for vaccination of this high risk group and/or pre-emptive anti-viral therapy.