The Burden of Influenza-Associated Critical Illness Hospitalizations*

Abstract

Objective Influenza is the most common vaccine-preventable disease in the United States; however, little is known about the burden of critical illness due to influenza virus infection. Our primary objective was to estimate the proportion of all critical illness hospitalizations that are attributable to seasonal influenza. Design Retrospective cohort study Setting Arizona, California, and Washington from January 2003 through March 2009 Patients All adults hospitalized with critical illness, defined by ICD-9-CM diagnosis and procedure codes for acute respiratory failure, severe sepsis, or in-hospital death Measurements We combined the complete hospitalization discharge databases for three US states, regional influenza virus surveillance, and state census data. Using negative binomial regression models, we estimated the incidence rates of adult influenza-associated critical illness hospitalizations and compared them to all-cause event rates. We also compared modeled outcomes to ICD-9-CM-coded influenza hospitalizations to assess potential under-recognition of severe influenza disease. Main Results During the study period, we estimated that 26,760 influenza-associated critical illness hospitalizations (95% CI: 14,541, 47,464) occurred. The population-based incidence estimate for influenza-associated critical illness was 12.0 per 100,000 person-years (95% CI: 6.6, 21.6), or 1.3% (95%CI:0.7%, 2.3%) of all critical illness hospitalizations. During the influenza season, 3.4% (95%CI:1.9%, 5.8%) of all critical illness hospitalizations were attributable to influenza. There were only 2,612 critical illness hospitalizations with ICD-9-CM-coded influenza diagnoses, suggesting influenza is either undiagnosed or under-coded in a substantial proportion of critical illness. Conclusions Extrapolating our data to the 2010 US population, we estimate about 28,000 adults are hospitalized for influenza-associated critical illness annually. Influenza in many of these critically ill patients may be undiagnosed. Critical care physicians should have a high index of suspicion for influenza in the ICU, particularly when influenza is known to be circulating in their communities.

Burden of influenza, respiratory syncytial virus, and other respiratory viruses and the completeness of respiratory viral identification among respiratory inpatients, Canada, 2003‐2014

“…A similar regression‐based study by Ortiz et al20 found only 1 of 10 influenza‐associated critical illness hospitalizations included an influenza diagnosis (including clinical diagnoses of ILI), compared to our estimate of 1 of 3 for respiratory patients admitted to a special care unit. A US study by Zhou et al21 found similar patterns for influenza and RSV, noting that although the overall morbidity burden of influenza and RSV was similar, the age‐specific burdens differ dramatically.…”

The Intensive Care Global Study on Severe Acute Respiratory Infection (IC-GLOSSARI): a multicenter, multinational, 14-day inception cohort study

“…Ortiz and collaborators [32] Hospital 12 (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23) Limitation of therapy in-hospital, n (%) DNR 72 (11.9) WH/WD 57 (9.4) about 28,000 adults are hospitalized for influenza-associated critical illness in the USA annually. A recent biasadjusted meta-analysis [33] confirmed that influenza vaccine was effective in preventing hospitalization from influenza and/or pneumonia and all-cause mortality in community-dwelling elderly.…”

Broad-Range Antiviral Activity of Hydrogen Sulfide Against Highly Pathogenic RNA Viruses

“…It is estimated that approximately 28,000 of critical-illness hospitalizations are attributed annually to seasonal influenza17. The number of hospitalization increased to approximately 274,000 during 2009 H1N1 pandemic leading to more than 12,000 deaths in the USA only18.…”