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Abstract

Background: We aimed to estimate the proportion of children hospitalized for influenza whose illness was complicated by bloodstream infection, describe their clinical course, and identify factors associated with bloodstream infection. Methods: We performed active surveillance for laboratory-confirmed influenza hospitalizations among children ≤16 years old at the 12 Canadian Immunization Monitoring Program Active hospitals, from the 2010-2011 to 2020-2021 influenza seasons. Factors associated with bloodstream infection were identified using multivariable logistic regression analyses. Results: Among 9,179 laboratory-confirmed influenza hospital admissions, bloodstream infection occurred in 87 children (0.9%). Streptococcus pyogenes (22%), Staphylococcus aureus (18%), and Streptococcus pneumoniae (17%) were the most common bloodstream infection pathogens identified. Children with cancer (adjusted odds ratio [aOR] 2.78, 95% confidence interval [CI] 1.23-5.63), a laboratory-confirmed non-bloodstream bacterial infection (aOR 14.1, 95% CI 8.04-24.3), or radiographically-confirmed pneumonia (aOR 1.87, 95% CI 1.17-2.97), were more likely to experience a bloodstream infection, whereas children with chronic lung disorders were less likely (aOR 0.41, 95% CI 0.19-0.80). Disease severity markers such as ICU admission (aOR 2.11, 95% CI 1.27-3.46), mechanical ventilation (aOR 2.84, 95% CI 1.63-4.80) and longer hospital length of stay (aOR 1.02, 95% CI 1.01-1.03) were associated with bloodstream infection. Bloodstream infection also increased the odds of death (aOR 13.0, 95% CI 4.84-29.1) after adjustment for age, influenza virus type and the presence of any at-risk chronic condition. Conclusions: Bloodstream infections, although infrequent, are associated with ICU admission, mechanical ventilation, increased hospital length of stay, and in-hospital mortality, thus requiring increased levels of care among pediatric influenza hospitalizations.