Influenza Clinical Practice Guidelines (2019)

Infectious Diseases Society of America (IDSA)

Reviewed and summarized by Medscape editors

February 05, 2019

Guidelines on the diagnosis and treatment of influenza were released on December 19, 2018, by the Infectious Diseases Society of America (IDSA). These clinical practice guidelines are an update to the guidelines published by the IDSA in 2009, prior to the 2009 H1N1 influenza pandemic. These guidelines discuss new information regarding diagnostic testing and treatment and chemoprophylaxis with antiviral medications.[1]

Influenza Testing

Influenza testing in outpatients (including emergency department patients)

During influenza activity, the following patient populations should undergo influenza testing:

  • High-risk patients, including immunocompromised individuals with influenzalike illness, pneumonia, or nonspecific respiratory illness if testing results would affect clinical management

  • Patients with acute-onset respiratory symptoms (with or without fever) and either exacerbated chronic medical conditions or known influenza complications if testing results would affect clinical management

Influenza testing in hospitalized patients

During influenza activity, influenza testing should be performed in the following cases:

  • Upon admission in all patients with acute respiratory illness, including pneumonia (with or without fever) who require hospitalization

  • Upon admission in all patients with chronic cardiopulmonary disease that is acutely worsening

  • Upon admission in all immunocompromised patients or in patients at high risk of complications who have acute-onset respiratory symptoms (with or without fever)

  • All hospitalized patients who develop acute-onset respiratory symptoms (with or without fever) or respiratory distress without a clear alternative diagnosis

During periods of low influenza activity, influenza testing should be performed upon admission in all patients who require hospitalization with acute respiratory illness (with or without fever), who have been in contact with a person diagnosed with influenza, or who have recently traveled from a location known to have influenza activity.

Specimen collection

In outpatients, specimens from the upper respiratory tract should be collected as soon as possible after illness, preferably within 4 days of symptom onset. Nasopharyngeal specimens are preferred; if they are unavailable, throat and nasal swabs should be collected and combined for influenza testing. Mid-turbinate nasal swab specimens are preferred over throat swab specimens. Flocked swab specimens are preferred over nonflocked swab specimens.

In hospitalized patients without severe lower respiratory tract disease, nasopharyngeal, mid-turbinate nasal, or combined nasal-throat specimens should be collected for influenza testing as soon as possible.

In hospitalized patients with respiratory failure who are receiving mechanical ventilation, including those in whom influenza testing results were negative based on upper respiratory tract specimens, endotracheal aspirate or bronchoalveolar lavage fluid specimens should be collected for influenza testing as soon as possible.

Specimens from nonrespiratory sites should not be collected for influenza testing.

Serum specimens, including single or paired sera, should not be collected for serological diagnosis of seasonal influenza virus infection for clinical management purposes.

Preferred testing methods

In outpatients, rapid molecular assays (ie, nucleic acid amplification tests) are preferred over rapid influenza diagnostic tests (RIDTs).

In hospitalized patients, reverse-transcription polymerase chain reaction (RT-PCR) or other molecular assays are preferred over other influenza tests. In hospitalized patients who are immunocompromised, multiplex RT-PCR assays targeting a panel of respiratory pathogens, including influenza viruses, should be used.

Immunofluorescence assays should not be used for influenza virus antigen detection in hospitalized patients unless more-sensitive molecular assays are unavailable; negative immunofluorescence test results should be confirmed with RT-PCR or other molecular assays.

RIDTs should not be used in hospitalized patients unless more sensitive molecular assays are unavailable; negative RIDT results should be confirmed with RT-PCR or other molecular assays.

Viral culture should not be used for initial or primary diagnosis of influenza.

Serologic testing should not be used to diagnose influenza.

Antiviral Therapy

High-risk individuals

Clinicians should initiate antivirals as soon as possible for adults and children with documented or suspected influenza, irrespective of influenza vaccination history, with the following:

  • Hospitalized with influenza, regardless of illness duration before hospitalization

  • Outpatients with severe or progressive illness, regardless of illness duration

  • Children younger than 2 years and adults aged 65 years or older

  • Women who are pregnant or within 2 weeks postpartum

Individuals not at high risk

Clinicians may consider antivirals for individuals with documented or suspected influenza, irrespective of influenza vaccination history, in the following patients:

  • Outpatients with illness onset 2 days or less

  • Symptomatic outpatients with household contacts at high risk

  • Symptomatic healthcare providers who care for patients at high risk, particularly those who are severely immunocompromised

Preferred antiviral regimens

Antiviral treatment with a single neuraminidase inhibitor (NAI) (oral oseltamivir, inhaled zanamivir, or intravenous peramivir) should be initiated as soon as possible.

Higher doses of FDA-approved NAI drugs should not be used routinely to treat seasonal influenza.

Uncomplicated influenza in an otherwise healthy ambulatory patient should be treated for 5 days with oral oseltamivir or inhaled zanamivir or a single dose of intravenous peramivir.

Considerations in cases of treatment failure or deterioration

Bacterial coinfection should be sought and empirically treated (1) in patients with suspected or laboratory-confirmed influenza whose presentation is severe initially, in addition to antiviral treatment for influenza and (2) in patients who deteriorate after initial improvement, particularly while receiving antiviral therapy.

In cases that fail to improve or deteriorate despite antiviral treatment, causes other than influenza should be ruled out.

Antiviral chemoprophylaxis

Antivirals should not be used for routine or widespread chemoprophylaxis outside of institutional outbreaks; antiviral chemoprophylaxis can be considered in the following circumstances:

  • The duration of influenza season in adults and children aged 3 months or older who are at very high risk of complications and for whom influenza vaccination is contraindicated, unavailable, or expected to have low effectiveness

  • The duration of influenza season in adults and children aged 3 months or older who are at the highest risk of influenza-associated complications (eg, HSCT recipients)

  • Short-term prophylaxis in addition to prompt flu vaccination in unvaccinated individuals at high risk as previously described or who are in contact with high-risk individuals

For more information, please go to Influenza.

For more Clinical Practice Guidelines, please go to Guidelines.

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