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Influenza

The Health Department provides resources and information for providers about how to treat, report and vaccinate against influenza.

Clinical Management

In most cases, laboratory diagnostic testing to determine if a patient has influenza (or which type or subtype) will not be available in time for providers to make clinical decisions. Clinicians should always use clinical judgment when deciding on care. When influenza is circulating in the community, use surveillance data to guide clinical decisions.

Treatment

Most cases of influenza are mild, and most patients can be managed in the outpatient setting or over the telephone. Patients who have mild influenza-like illness (a fever of more than 100° F, with cough or sore throat) and are not at a high risk for severe illness and complications usually do not require antiviral medication, though clinicians may prescribe antivirals to these patients to reduce the number of days of influenza symptoms.

Patients should receive early empiric treatment with antiviral medications (ideally within 48 hours of illness onset) if they:

  • Have a severe illness, such as an unexplained acute febrile respiratory illness.
  • Are hospitalized.
  • Have mild influenza-like illness but are in a high risk group.

Even if you cannot initiate treatment for these types of patients with 48 hours of illness onset, patients may still benefit from antiviral medication. All patients who are hospitalized for suspected or confirmed influenza should be treated, regardless of when the illness first presented.

Currently, the Health Department recommends the following drugs to treat influenza:

  • Oseltamivir
  • Zanamivir
  • Peramivir
  • Baloxavir

Diagnostic Testing

Diagnostic testing for influenza is generally not necessary for most patients with mild influenza-like illness.

Commercially available rapid test kits have poor sensitivity for detecting influenza. A positive result is indicative of infection, but a negative result should not be used to rule out influenza.

More sensitive assays, including RT-PCR, for subtyping of influenza A are available commercially, but they are not available at the point of care. Results of these tests may not be available within 48 hours of illness onset (i.e., in time for treatment decisions).

The NYC Public Health Laboratory does not accept individual specimens for influenza diagnostic testing, except as part of ongoing surveillance programs.

Pregnancy and Postpartum

Pregnant and postpartum people are at higher risk for severe illness and death from seasonal influenza. The Health Department strongly recommends that pregnant people get the seasonal influenza vaccine and be treated with antiviral medications as early as possible if they develop influenza-like illness.

Infants, Children, and Adolescents

Children under the age of 2 years are at higher risk for severe illness and complications from influenza and should be treated with antiviral medications as early as possible if they have suspected or confirmed influenza. Children who have underlying medical conditions should also be treated empirically and promptly with antivirals. All children older than 6 months of age should get the seasonal influenza vaccine. Use caution when prescribing pediatric oseltamivir suspension for children due to the risk of dosing errors. If shortages of oseltamivir suspension occur, the drug can be compounded.

Additional Resources

More Information