Review
Influenza epidemics: The role of allergists-immunologists

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Abstract

Objective

To review influenza epidemics and pandemics for practicing allergists-immunologists.

Data Sources

English-language articles published in PubMed from 1990 to present with relevance to allergic disorders and articles cited by or similar to these articles.

Study Selections

A total of 472 articles were identified from PubMed. Two independent reviewers appraised the titles for relevance.

Results

A total of 212 relevant articles were selected. Additional articles and government websites increased the number to 295 relevant citations.

Conclusion

Influenza epidemics and pandemics have recurred throughout history. Patients with asthma and immunodeficiency are at an increased risk. Nonpharmaceutical interventions, vaccination, and neuraminidase inhibitors are key strategies for the prevention and treatment of influenza epidemics/pandemics. Allergists play a vital role in protecting high-risk groups and increasing influenza vaccination coverage.

Introduction

Influenza epidemics have occurred throughout recorded history and are likely to recur. Reviewing the history of influenza epidemics and pandemics is important for practicing allergists because we care for high-risk patients, including those with asthma and immunodeficiencies.

Our objective is to review influenza epidemics and pandemics for practicing allergists-immunologists. We searched for English-language articles published in PubMed from 1990 to present with relevance to allergic disorders and articles cited by or similar to these. We used the Medical Subject Headings (MESH) terms ((“Influenza, Human”[Mesh] OR “Influenza Pandemic, 1918-1919”[Mesh] OR influenza∗[tiab] OR flu[tiab]) AND (“Epidemics”[Mesh] OR epidemic∗[tiab] OR pandemic∗[tiab])) AND (“Hypersensitivity”[Mesh] OR allergy[tiab] OR allergies[tiab] OR “allergic reaction”[tiab] OR “allergic reactions”[tiab] OR “Rhinitis, Allergic”[Mesh] OR rhinitis[tiab] OR “Asthma”[Mesh] OR asthma∗[tiab] OR “Sinusitis”[Mesh] OR sinusitis[tiab] OR “sinus infection”[tiab] OR “sinus infections”[tiab] OR “Allergy and Immunology”[Mesh] OR immunology[tiab]). A total of 472 articles were identified from PubMed. Two independent reviewers appraised the titles for relevance. A third independent reviewer resolved any discrepancies between the reviewers. A total of 212 relevant articles were selected. Additional articles and government websites increased the number to 295 relevant citations that were reviewed in detail.

Section snippets

Classification of Influenza Virus

Influenza viruses belong to a family of RNA viruses called Orthomyxoviridae. Influenza tends to be classified into 3 types of viruses—A, B, and C—each with different natural hosts and unique serologic responses to their internal proteins. Birds tend to be the natural host for influenza A, whereas influenza B and C are mostly restricted to humans.1 Type C tends to cause much less severe disease in humans, with mild symptoms similar to those found with the common cold.2

Influenza A, owing to its

Influenza Outbreaks before the 20th Century

The influenza virus has caused epidemics and pandemics for many centuries. Although pandemics lead to virus spread on a global scale, epidemics are found when there is a spike in infection rates at the local level, often after seasonal patterns of infection. The influenza virus was not identified and isolated until the 20th century; however, there is little doubt that numerous outbreaks occurred for centuries before that. An outbreak in 1580 is often referred to as the first influenza pandemic.

Effects of Influenza on Asthma

Asthma affects 339 million people of all ages worldwide and is the leading cause of chronic disease in children.22 It has long been understood that viral infections can lead to asthma exacerbations in all age ranges. Influenza is detected in up to 20% of acute wheezing illnesses in pediatrics and up to 25% in acute asthma exacerbations in adults.23 In addition to exacerbations, influenza increases hospitalization rate in patients with asthma. In a study of 6- to 23-month-old children, the rate

Prevention and Treatment of Influenza

The influenza virus has the potential to cause annual epidemics and global pandemics. Antigenic drift results from the accumulation of minor mutations in the genes that encode some of the antibody-binding sites located on the influenza virus. A virus strain can develop several of these minor mutations, allowing it to evade the immune system and cause annual epidemics. In contrast, the influenza virus also has the potential to undergo a more rapid and radical change in viral antigenicity, most

Role of the Allergist-Immunologist in Preventing Influenza Epidemics

The role of the allergist-immunologist in influenza epidemics is a unique one in that it entails expertise in asthma and immune deficiencies, thereby playing a crucial role in upholding the health status of 2 of the most vulnerable populations to influenza illnesses.

The CDC recommends vaccinating all patients with asthma above the age of 6 months. Influenza vaccination rates among people with asthma range widely in varying parts of the world. It has been reported below 50% in adults and

Conclusion

Influenza virus is under constant pressure to evade immune responses. In evading the immune response, small changes in influenza lead to determining the major prevalent seasonal strain. Bigger changes in influenza can lead to epidemics and pandemics. Allergists are in a unique position to protect vulnerable patients, including those with asthma and immunodeficiencies, with the use of vaccinations and NA inhibitors that can prevent and treat influenza infections. Allergists can increase

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    Disclosures: The authors have no conflicts of interest to report.

    Funding: The authors have no funding sources to report.

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