This interim guidance provides recommendations for antiviral treatment of confirmed cases, probable cases, and cases under investigation of human infection with avian influenza A(H7N9) virus in the United States (updates on the latest information on H7N9 are available at Avian Influenza A (H7N9) Virus). These recommendations were developed by experts at the Centers for Disease Control and Prevention (CDC), in consultation with non-CDC influenza antiviral experts, and are based upon expert opinion and all available data on the treatment of seasonal, pandemic, and zoonotic influenza. This guidance will be updated as additional information on H7N9 virus transmissibility, epidemiology, and antiviral susceptibility patterns becomes available.
These interim recommendations are based upon current information and the following considerations:
- Current lack of a vaccine for H7N9 virus
- Severe H7N9 disease with substantial mortality to date
- Limited current human-to-human H7N9 virus transmission but potential for increased transmission in the future
Clinicians should consider the possibility of avian influenza A(H7N9) virus infection in persons presenting with acute febrile respiratory illness and an appropriate recent travel or exposure history (see Interim Guidance on Case Definitions to be Used for Novel Influenza A (H7N9) Case Investigations in the United States).
Randomized controlled trials of currently approved influenza antivirals have demonstrated decreased time to symptom improvement when used to treat otherwise healthy persons with acute uncomplicated influenza caused by circulating seasonal influenza strains within the first few days of illness [1-9]. On the basis of these trials and additional pooled analyses and observational studies [10-12], many experts believe that when antiviral agents are given early in the course of uncomplicated influenza illness, both the duration of symptoms and the likelihood of complications are reduced. Clinical benefit is greatest when antiviral treatment is administered early, especially within 48 hours of influenza illness onset [1-16]. Among patients hospitalized with seasonal influenza A (including 2009 H1N1) or B, or avian influenza A(H5N1) virus infections, observational studies suggest that early treatment reduces disease severity and mortality [17-26]. Although earlier antiviral treatment results in greater clinical benefit, observational studies support the use of antiviral treatment in hospitalized patients even when started after 48 hours of illness [17, 27-33].
While no data are available regarding early neuraminidase inhibitor treatment of persons infected with H7N9 virus, laboratory testing with functional assays indicates that H7N9 viruses are susceptible to neuraminidase inhibitors (oseltamivir and zanamivir), but resistant to adamantanes (amantadine and rimantadine). Therefore, amantadine and rimantadine are not recommended for treatment of H7N9 virus infection.
Influenza Antiviral Treatment Recommendations
- Because of the potential severity of illness associated with H7N9 virus infection, it is recommended that all confirmed cases, probable cases, and H7N9 cases under investigation (see Interim Guidance on Case Definitions to be Used for Novel Influenza A (H7N9) Case Investigations in the United States) receive antiviral treatment with a neuraminidase inhibitor as early as possible. Treatment should be initiated even if it is more than 48 hours after onset of illness.
- Laboratory testing and initiation of antiviral treatment should occur simultaneously;treatment should not be delayed for laboratory confirmation of influenza or H7N9 infection. (For information regarding case investigation, specimen collection and laboratory testing, please see theCDC Health Alert Network issued on April 5, 2013.
- Please see Antiviral Drugs: Dosage (ACIP) for additional guidance on the use of influenza antiviral agents, including dosage recommendations for treatment by age group. Oseltamivir is recommended for treatment of persons of any age; zanamivir is recommended for children aged 7 and older. Clinicians may refer to the manufacturer’s package inserts for additional information regarding dosing, contraindications, and potential adverse events.
Uncomplicated Illness in Outpatients
- Given the anticipated lack of preexisting immunity to H7N9 viruses, the potential for rapid progression, severe disease, and fatal outcomes with H7N9 infection, and low adverse event profile of neuraminidase inhibitors, treatment with oseltamivir or inhaled zanamivir should be initiated when confirmed cases, probable cases, or H7N9 cases under investigation are recognized, even if more than 48 hours from illness onset and even for apparently uncomplicated illness.
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Hospitalized Patients
- Initiation of antiviral treatment is recommended as early as possible for hospitalized patients, even if more than 48 hours from illness onset.
- For hospitalized patients and patients with severe or complicated illness, treatment with oral oseltamivir (and not inhaled zanamivir) is recommended because of the lack of data for inhaled zanamivir in patients with severe influenza illness.
- The optimal duration and dose of therapy are uncertain in severe or complicated influenza. Pending further data, longer courses of treatment (e.g., 10 days of treatment) should be considered for severely ill hospitalized H7N9 patients...
- http://www.cdc.gov/flu/avianflu/h7n9-antiviral-treatment.htm
