Influenza Update: IDSA 2018 Guidelines Detailed Review

Symptomatic influenza A and B infections cause worldwide morbidity and mortality every year. Annual vaccination remains the greatest prophylactic measure, but the vaccine is not 100% effective due to mismatch between the circulating and vaccine virus strains. Although most individuals will recover from influenza without incident, some specific patient populations are at high risk for severe complications. The Infectious Disease Society of America (IDSA) recently updated their clinical practice guidelines.¹ We review these key updates, including recommendations on who to test, treat, and provide chemoprophylaxis.

Context

This is the first ALiEM post on influenza testing and treatment since 2014. At that time, we concluded that some of the neuraminidase inhibitors (e.g. oseltamivir) showed only modest decreases in time to symptom alleviation compared to placebo. However, these medications did not reduce the risk of subsequent complications from influenza. Further, trials did not compare to standard therapies (e.g. acetaminophen or NSAIDs). We outlined further points of controversy related to Roche pharmaceuticals.

This post does not endorse these guidelines, but we think it’s important to report them. Anti-viral therapies for influenza is a promising area of research, but requires further scrutiny and heightened transparency. Understanding these guidelines informs our EM community so that we can take part in the continued debate around the efficacy of anti-viral therapy for influenza. To understand the grading system for these recommendations, we highly recommend Dr. Ryan Radecki’s fantastic review and analysis.

Who To Test for Influenza

If the result will influence management, then testing should be performed in patients who present with influenza-like illness, pneumonia, or nonspecific respiratory symptoms and are:

1. High-risk patients, including those with compromised immune systems (independent of the duration of symptoms).
2. Patients with exacerbations of their known chronic medical conditions or with a potential complication of influenza (such as pneumonia).
3. Patients who are not at high risk for complications, but results may influence decision to discharge home, time in the ED, or chemoprophylaxis decisions for high-risk household contacts.

Who Should We Treat with Anti-Virals

Independent of illness duration, providers should treat patients who are:

1. Hospitalized with influenza. (A-II)
2. Managed as an outpatient, but have severe or progressive illness. (A-III)
3. Managed as an outpatient, but high risk for complications from influenza. (A-II)

Who Should We Also Consider Treating

The IDSA also recommends that we consider treatment for adults and children not at high risk of complications. These include:

1. Outpatients with illness onset ≤ 2 days before presentation (C-I).
2. Symptomatic outpatients who are household contacts of persons who are at high risk of developing complications from influenza, particularly those who are severely immunocompromised (C-III).
3. Symptomatic healthcare providers who care for patients who are at high risk of developing complications from influenza, particularly those who are severely immune-compromised (C-III).

Influenza Treatment Recommendations

Treatment options for uncomplicated influenza in otherwise healthy ambulatory patients include:

• Oral oseltamivir (Tamiflu®)
• Inhaled zanamivir (Relenza®), or
• A single dose of intravenous peramivir (Rapivab®).

Oral oseltamivir is preferred in:

1. Pregnant patients
2. Hospitalized patients
3. Those with severe or complicated illness with suspected or confirmed influenza

Other Treatment Pearls

1. Providers may consider extending the duration of antiviral treatment for patients with known or suspected compromise to their immune system, or will require hospitalization for severe lower respiratory tract disease (A-III).
2. The FDA recently approved oral baloxavir marboxil (Xofluza®) for the treatment of influenza A and B in patients 12 years and older. The CDC provides additional information on this new medication.
3. Corticosteroids and immunoglobulin therapies (e.g. IVIG) are not recommended for treating adults or children with influenza or related complications.

Take-Home Points

• Test for influenza when the results are anticipated to influence your management or a public health response.
• Test with molecular assays that rapidly detect influenza A and B viral RNA in respiratory specimens.
• Patients at high risk for influenza complications or ill enough to require hospitalization for flu symptoms should undergo prompt testing and receive treatment even if symptom duration is >2 days.
• Patients who are low risk for complications of influenza and test positive should only be treated if symptomatic for <2 days.

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