Influenza in Asthmatics: For Better or for Worse?

Abstract

Asthma and influenza are two pathologic conditions of the respiratory tract that affect millions worldwide. Influenza virus of the 2009 pandemic was highly transmissible and caused severe respiratory disease in young and middle-aged individuals. Asthma was discovered to be an underlying co-morbidity that led to hospitalizations during this influenza pandemic albeit with less severe outcomes. However, animal studies that investigated the relationship between allergic inflammation and pandemic (p)H1N1 infection, showed that while characteristics of allergic airways disease were exacerbated by this virus, governing immune responses that cause exacerbations may actually protect the host from severe outcomes associated with influenza. To better understand the relationship between asthma and severe influenza during the last pandemic, we conducted a systematic literature review of reports on hospitalized patients with asthma as a co-morbid condition during the pH1N1 season. Herein, we report that numerous other underlying conditions, such as cardiovascular, neurologic, and metabolic diseases may have been underplayed as major drivers of severe influenza during the 2009 pandemic. This review synopses, (1) asthma and influenza independently, (2) epidemiologic data surrounding asthma during the 2009 influenza pandemic, and (3) recent advances in our understanding of allergic host–pathogen interactions in the context of allergic airways disease and influenza in mouse models. Our goal is to showcase possible immunological benefits of allergic airways inflammation as countermeasures for influenza virus infections as a learning tool to discover novel pathways that can enhance our ability to hinder influenza virus replication and host pathology induced thereof.

Beyond Respiratory Syncytial Virus and Rhinovirus in the Pathogenesis and Exacerbation of Asthma

“…Having asthma was found to be a risk factor for hospitalization for H1N1 59,60 and was found in 10% to 20% of the hospitalized patients worldwide. 61 Nonetheless, an observation has also been made that having asthma may be protective once patients are hospitalized from influenza. Patients with asthma had decreased risk of ICU stay, mechanical ventilation, and death from H1N1, compared with other chronic conditions, such as cardiovascular diseases and obesity.…”

Contrasting Effects of Adipokines on the Cytokine Production by Primary Human Bronchial Epithelial Cells: Inhibitory Effects of Adiponectin

“…When influenza viruses infect the airway epithelium, they trigger crucial innate and adaptive immune antiviral responses. The interaction between respiratory viruses and airway epithelial cells results in production of antiviral substances, cytokines, and chemokines, which recruit inflammatory cells and influence the innate and adaptive immunity (Vareille et al, 2011;Herold et al, 2015;Veerapandian et al, 2018). With respect to asthma, the evidence for epithelial dysregulation is compelling; and the consensus is that the initiating trigger occurs at the bronchial epithelium (Vareille et al, 2011;Herold et al, 2015).…”

Eosinophils and Respiratory Viruses

“…Influenza virus induces acute asthma exacerbations in children and adults, especially during annual seasons (90). Interestingly, among patients hospitalized during the 2009 influenza pandemic, patients with asthma had less severe outcomes related to viral infection compared with non-asthmatics (10,31,73,81,83), although the asthma phenotype of these patients was not reported (130).…”