|About This Issue|
|Table of Contents|
Emergency clinicians must be aware of the current diagnostic and therapeutic recommendations for influenza and the available resources to guide management. This comprehensive review outlines the classification of influenza viruses, influenza pathophysiology, the identification of high-risk patients, and the importance of vaccination. Seasonal variations of influenza are discussed, as well as the rationale for limiting testing during periods of high prevalence. Differences between strains of influenza are discussed, as well as the challenges in achieving optimal vaccine effectiveness. Recommendations for use of the currently available oral, intranasal, and intravenous antiviral treatments are provided, as well as utilizing shared decision-making with patients regarding risks and benefits of treatment.
A 20-month-old boy presents to the ED with a cough and fever for 3 days. He has no past medical history, and his routine vaccinations are up-to-date. His parents say he has been eating less than usual; however, his urine output is normal, and he has had no vomiting or diarrhea. Vital signs are: temperature, 39.6ËšC (103.2°F); heart rate, 156 beats/min; respiratory rate, 32 breaths/ min; and oxygen saturation, 100% on room air. He is well-appearing, although his left tympanic membrane is erythematous and bulging, with apparent middle-ear purulence. You make the diagnosis of otitis media in the setting of a presumed viral upper respiratory infection. While preparing the discharge papers, you consider the many patients you’ve seen during the current flu epidemic and wonder whether treatment for influenza would be appropriate . . .
Your next patient is a 32-year-old man with the same chief complaints: cough and fever. His maximum temperature over the past 5 days was 40ËšC (103.9°F). He has been taking over-the-counter cold remedies without relief, and today he is markedly short of breath. The patient has no regular primary care provider and has no significant past medical history. His initial vital signs are: temperature 39.2ËšC (102.5°F); heart rate, 118 beats/min; respiratory rate, 28 breaths/min; blood pressure, 134/78 mm Hg; and oxygen saturation, 88% on room air. On examination, he appears uncomfortable, with notable tachypnea. The oropharynx is clear and the neck supple. Crackles are noted in the right lower lung field, without any wheezing. The abdomen is soft and nontender. The patient is given oxygen via face mask, with an improvement in saturation to 100%. Chest x-ray reveals a right lower lobar pneumonia with a small pleural effusion. You start IV antibiotics and request an inpatient bed, as he is hypoxic with his pneumonia. You wonder whether influenza testing is indicated, and if so, what type of test, and how reliable would it be?
During the 1918–1919 influenza pandemic, approximately one-third of the world’s population was infected and approximately 50 million people died.1 At that time, influenza pandemics were not new occurrences, but their mortality and morbidity had not been well documented and the causative organisms had not been identified. Fifty years later, it was estimated that the 1968 “Hong Kong” influenza pandemic (H3N2) caused between 1 and 4 million deaths worldwide. Despite advances in diagnostic and treatment strategies, mortality from influenza continues to increase, with over 30,000 deaths annually in the United States, partly related to the aging of the population.2 With globalization, the need to contain regional influenza outbreaks has assumed more urgency to prevent an emerging pandemic. The emergency department (ED) plays a key role in disease outbreaks, since containment of a potential epidemic relies on early and rapid identification, treatment, and—in some cases—prophylaxis.
The medical costs and lost wages from influenza are substantial. According to the United States Centers for Disease Control and Prevention (CDC), influenza epidemics cost $10.4 billion per year in direct medical expenses and an additional $16.3 billion in lost earnings annually in the United States.3,4 An influenza epidemic is responsible for 3.1 million hospitalized days, and 31.4 million outpatient visits annually (during the epidemic), with a total economic burden of $87.1 billion in the United States alone.4
As the public health community commemorates the 50th and 100th anniversaries of historic and tragic influenza pandemics, this issue of Emergency Medicine Practice presents an update based on a critical appraisal of the most current literature on influenza. Recent studies on clinical presentation, diagnosis, and treatment are reviewed, and recommendations on the evaluation and management of patients with suspected symptoms of influenza are provided.
PubMed, ISI Web of Knowledge, and the Cochrane Database of Systematic Reviews resources from 2012 to 2018 were accessed using the keywords: emergency department, epidemic, pandemic, influenza, novel H1N1, and H3N2. The CDC5 and the World Health Organization (WHO)6 websites were accessed. Guidelines from the American College of Emergency Physicians (ACEP),7 the Infectious Diseases Society of America (IDSA),8 and the American Academy of Pediatrics (AAP)9 were also reviewed. References from the literature were searched to identify additional content.
2. “The patient had an infiltrate on chest x-ray, so bacterial pneumonia appeared to be the clear diagnosis.”
Numerous secondary complications can stem from a primary influenza infection. When addressing and treating these complications, do not overlook the possibility of a primary influenza infection and the need for medical management. In certain clinical situations, treatment with antiviral medications as well as antibacterial medications may be indicated.
5. “My patient is pregnant and has influenza. The side-effect profile of antiviral medications concerns me, so I feel better treating her with supportive care.”
Pregnancy is a risk factor for a more severe disease course during an influenza infection. Initial CDC epidemiologic data from the last 10 influenza seasons indicate that some of the highest rates of morbidity and mortality are among pregnant women, which confirms the necessity of antivirals in this population.
7. “Flu is everywhere. I don’t have the time to consult the CDC website. I will just give oseltamivir to my patient and be done with it.”
Even in times of epidemic influenza infection, numerous strains can be circulating at a given time within a particular region. In past epidemics, there have been reports of influenza strains resistant to oseltamivir. Thus, without knowing the prevalence of local strains, one might mistakenly choose an antiviral agent that will prove less effective on those strains. Treatment with more than 1 agent may even be indicated in some regions until more formal strain-specific diagnostic testing can be undertaken. Since certain medications are effective against only influenza type A, the local prevalence of any type B influenza should be determined in order to select the appropriate drug therapy.
Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.
To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study is included in bold type following the references, where available. In addition, the most informative references cited in this paper, as determined by the author, are highlighted.
Points and Pearls Excerpt
Most Important References
AL Giwa MD, MBA, FACEP, FAAEM; Chinwe Ogedegbe, MD, MPH, FACEP; Charles G. Murphy, MD
Michael K. Abraham, MD; Daniel J. Egan, MD
December 1, 2018
December 31, 2021
4 AMA PRA Category 1 Credits™, 4 ACEP Category I Credits, 4 AAFP Prescribed Credits, 4 AOA Category 2-A or 2-B Credits. Specialty CME Credits: Included as part of the 4 credits, this CME activity is eligible for 3 Pharmacology CME credits
Date of Original Release: December 1, 2018. Date of most recent review: November 15, 2018. Termination date: December 1, 2021.
Accreditation: EB Medicine is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. This activity has been planned and implemented in accordance with the accreditation requirements and policies of the ACCME.
Credit Designation: EB Medicine designates this enduring material for a maximum of 4 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
ACEP Accreditation: Emergency Medicine Practice is approved by the American College of Emergency Physicians for 48 hours of ACEP Category I credit per annual subscription.
AAFP Accreditation: This Enduring Material activity, Emergency Medicine Practice, has been reviewed and is acceptable for credit by the American Academy of Family Physicians. Term of approval begins 07/01/2017. Term of approval is for one year from this date. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Approved for 4 AAFP Prescribed credits.
AOA Accreditation: Emergency Medicine Practice is eligible for up to 48 American Osteopathic Association Category 2-A or 2-B credit hours per year.
Specialty CME: Included as part of the 4 credits, this CME activity is eligible for 3 Pharmacology CME credits, subject to your state and institutional approval.
Needs Assessment: The need for this educational activity was determined by a survey of medical staff, including the editorial board of this publication; review of morbidity and mortality data from the CDC, AHA, NCHS, and ACEP; and evaluation of prior activities for emergency physicians.
Target Audience: This enduring material is designed for emergency medicine physicians, physician assistants, nurse practitioners, and residents.
Goals: Upon completion of this activity, you should be able to: (1) demonstrate medical decision-making based on the strongest clinical evidence; (2) cost-effectively diagnose and treat the most critical presentations; and (3) describe the most common medicolegal pitfalls for each topic covered.
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