Influenza Virus-Related Critical Illness: Prevention, Diagnosis, Treatment Eric J
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Chow et al. Critical Care (2019) 23:214 https://doi.org/10.1186/s13054-019-2491-9 REVIEW Open Access Influenza virus-related critical illness: prevention, diagnosis, treatment Eric J. Chow1,2, Joshua D. Doyle1,2 and Timothy M. Uyeki2* Abstract Annual seasonal influenza epidemics of variable severity result in significant morbidity and mortality in the United States (U.S.) and worldwide. In temperate climate countries, including the U.S., influenza activity peaks during the winter months. Annual influenza vaccination is recommended for all persons in the U.S. aged 6 months and older, and among those at increased risk for influenza-related complications in other parts of the world (e.g. young children, elderly). Observational studies have reported effectiveness of influenza vaccination to reduce the risks of severe disease requiring hospitalization, intensive care unit admission, and death. A diagnosis of influenza should be considered in critically ill patients admitted with complications such as exacerbation of underlying chronic comorbidities, community-acquired pneumonia, and respiratory failure during influenza season. Molecular tests are recommended for influenza testing of respiratory specimens in hospitalized patients. Antigen detection assays are not recommended in critically ill patients because of lower sensitivity; negative results of these tests should not be used to make clinical decisions, and respiratory specimens should be tested for influenza by molecular assays. Because critically ill patients with lower respiratory tract disease may have cleared influenza virus in the upper respiratory tract, but have prolonged influenza viral replication in the lower respiratory tract, an endotracheal aspirate (preferentially) or bronchoalveolar lavage fluid specimen (if collected for other diagnostic purposes) should be tested by molecular assay for detection of influenza viruses. Observational studies have reported that antiviral treatment of critically ill adult influenza patients with a neuraminidase inhibitor is associated with survival benefit. Since earlier initiation of antiviral treatment is associated with the greatest clinical benefit, standard-dose oseltamivir (75 mg twice daily in adults) for enteric administration is recommended as soon as possible as it is well absorbed in critically ill patients. Based upon observational data that suggest harms, adjunctive corticosteroid treatment is currently not recommended for children or adults hospitalized with influenza, including critically ill patients, unless clinically indicated for another reason, such as treatment of asthma or COPD exacerbation, or septic shock. A number of pharmaceutical agents are in development for treatment of severe influenza. Keywords: Influenza, Influenza vaccination, Influenza testing, Antiviral treatment Background have self-limited uncomplicated upper respiratory tract Annual seasonal influenza epidemics of variable severity illness. One study estimated that during 2010–2016, ap- result in significant morbidity and mortality in the proximately 8.3% of the U.S. population experienced United States (U.S.) and worldwide [1–3]. In temperate symptomatic influenza each year [7]. However, compli- climate countries, including the U.S., influenza activity cations may result in severe illness, including fatal out- peaks during the winter months whereas in tropical re- comes. During 2010–2018, an estimated 4.3–23 million gions influenza activity may be more variable [4–6]. medical visits, 140,000–960,000 hospitalizations, and 12, Most persons with symptomatic influenza virus infection 000–79,000 deaths were associated with influenza each year in the U.S. [8]. Another study estimated that 18, * Correspondence: [email protected] 000–96,000 influenza-related intensive care unit (ICU) 2Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Mailstop H24-7, 1600 admissions occur annually in the U.S. [9]. There are an Clifton Road, N.E., Atlanta, GA 30329, USA estimated 291,000–646,000 respiratory deaths attributed Full list of author information is available at the end of the article © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Chow et al. Critical Care (2019) 23:214 Page 2 of 11 to seasonal influenza each year worldwide [2]. Here, we Table 2 Groups at high risk for influenza complications* review strategies for prevention, diagnosis, and treat- Risk factors for severe influenza outcomes ment of influenza virus infections in the ICU (Table 1). • Age < 5 years, especially those < 2 years • Age > 65 years Risk factors • Pregnant women Influenza vaccination is the primary method for prevent- • 2 ing influenza and reducing the risk of severe outcomes. Extreme obesity (BMI > 40 kg/m ) In the U.S., the Advisory Committee on Immunization • Native Americans/Alaskan Natives (may also apply to indigenous Practices (ACIP) recommends annual influenza vaccin- people from other countries) ation for all persons aged 6 months and older and priori- • Current or past tobacco use tizes those at higher risk for influenza complications • Children and adolescents receiving aspirin or salicylate-containing [10]. High-risk groups include adults aged > 65 years [11, medications who might be at risk for Reye syndrome 12], children aged < 5 years (particularly those aged < 2 • Underlying chronic medical conditions: years) [13, 14], pregnant women (up to 2 weeks post- ○ Pulmonary partum) [15–18], persons with certain chronic medical ○ Cardiovascular 1 conditions, Native Americans/Alaska Natives, and resi- ○ Renal dents of nursing homes and other long-term care facil- ○ Hepatic ities (Table 2). Studies have specifically highlighted that ○ those with chronic pulmonary, cardiovascular, renal, Neurologic hepatic, neurologic, hematologic or metabolic disorders, ○ Hematologic immunocompromised persons, children and adolescents ○ Metabolic receiving aspirin- or salicylate-containing medications ○ Immunocompromised state and who might be at risk for experiencing Reye syn- *From the U.S. Centers for Disease Control and Prevention Advisory drome with influenza virus infection, and those who are Committee on Immunization Practices extremely obese (BMI > 40) are at increased risk for influenza-related complications [10, 19–23]. influenza patients [24, 29]. In children, independent risk Many studies evaluated risk factors for severe influenza factors for influenza A(H1N1)pdm09-related mortality in- during the 2009 H1N1 influenza pandemic. Adult ICU pa- cluded chronic neurologic condition or immune com- tients with influenza A(H1N1)pdm09 virus infection were promise, acute myocarditis or encephalitis, and early primarily non-elderly, were obese [24–28], and had higher presumed MRSA co-infection of the lung [30]. Female odds of death, invasive mechanical ventilation, acute re- gender was also identified as a risk factor; however, there spiratory distress syndrome (ARDS), septic shock, and was no gender difference in overall mortality. Bacterial co- multi-lobar pneumonia when compared with seasonal infection was identified in approximately one third of fatal influenza A(H1N1)pdm09 cases in the largest autopsy Table 1 Key points: care of patients with severe influenza case series [31]. Bacterial co-infections in the inter- Key Points pandemic period are also common in critically ill influ- • There are an estimated 291,000–646,000 seasonal influenza-associated enza patients [32]. One study identified past or current to- respiratory deaths every year worldwide. bacco use as a risk factor associated with ICU admission • Annual influenza vaccination is the primary method of preventing [33]. A recent multicenter cohort study reported that influenza and influenza-related complications, especially in high-risk persons. mortality was higher in immunosuppressed patients with influenza A(H1N1)pdm09 than in immunocompetent pa- • Influenza molecular diagnostic testing is recommended for all patients requiring hospitalization with suspected influenza. tients [34]. Severity of influenza seasons varies from year- • Influenza antiviral treatment should be started as soon as possible in to-year based on the predominant influenza viruses, and hospitalized patients with suspected influenza, including critically ill between seasonal and pandemic influenza [35, 36]. One patients, and should not be delayed while awaiting results of influenza study reported that patients with influenza A(H1N1) diagnostic tests. pdm09 had higher odds of severe disease than patients • Enterically administered oseltamivir is recommended for influenza with either influenza A(H3N2) or influenza B virus infec- patients except for those with contraindications (e.g., gastric stasis, ileus, malabsorption). tions [37]. However, influenza B virus infection has been shown to increase the odds of in-hospital mortality in chil- • Repeat virologic testing in lower respiratory tract specimens may be required to determine therapeutic