From the Guidelines
Influenza A diagnosis and treatment should prioritize antiviral medications like oseltamivir (Tamiflu) 75mg twice daily for 5 days, started ideally within 48 hours of symptom onset, especially for high-risk populations such as the elderly, pregnant women, young children, and those with chronic medical conditions, as recommended by the most recent guidelines 1.
Diagnosis
Influenza A diagnosis is typically confirmed through rapid antigen tests or PCR testing of respiratory specimens, with symptoms including fever, cough, sore throat, body aches, fatigue, and headache.
- Rapid antigen tests are commonly used for diagnosis due to their quick results and ease of use.
- PCR testing is more sensitive and specific, but may take longer to produce results.
Treatment
Treatment primarily involves antiviral medications, with oseltamivir being the first-line treatment.
- Oseltamivir (Tamiflu) 75mg twice daily for 5 days is the recommended dosage.
- Zanamivir (Relenza), peramivir (Rapivab), and baloxavir marboxil (Xofluza) are alternative antivirals for patients who cannot take oseltamivir.
- Supportive care is essential, including rest, adequate hydration, and fever control with acetaminophen (650mg every 4-6 hours) or ibuprofen (400-600mg every 6-8 hours).
High-Risk Populations
Certain populations are at higher risk for complications from influenza, including:
- Children younger than 2 years
- Adults ≥65 years
- Pregnant women and those within 2 weeks postpartum
- Persons with chronic medical conditions, such as chronic pulmonary, cardiovascular, renal, hepatic, hematological, or metabolic disorders
- Immunocompromised patients
Prevention
Prevention strategies include:
- Annual vaccination
- Hand hygiene
- Avoiding close contact with infected individuals
- Antivirals work by inhibiting viral replication, reducing symptom duration and severity while potentially preventing complications like pneumonia, especially in high-risk populations, as supported by recent guidelines 1.
From the FDA Drug Label
Oseltamivir phosphate for oral suspension is indicated for the treatment of acute, uncomplicated illness due to influenza A and B infection in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours. RELENZA, an influenza virus neuraminidase inhibitor (NAI), is indicated for: Treatment of acute, uncomplicated influenza type A and B infections in patients aged 7 years and older who have been symptomatic for no more than 2 days.
The diagnosis of Influenza A is not explicitly stated in the provided drug labels. The treatment options for Influenza A include:
- Oseltamivir phosphate for oral suspension for patients 2 weeks of age and older who have been symptomatic for no more than 48 hours 2
- Zanamivir (RELENZA) for patients aged 7 years and older who have been symptomatic for no more than 2 days 3 Key considerations:
- These medications are not recommended for certain patient populations, such as those with underlying airways disease (zanamivir) or end-stage renal disease not undergoing dialysis (oseltamivir phosphate)
- The medications are not a substitute for annual influenza vaccination.
From the Research
Diagnosis of Influenza A
- The diagnosis of influenza A is typically made clinically, based on symptoms such as abrupt onset of fever, cough, chills or sweats, myalgias, and malaise 4
- Laboratory testing, such as rapid molecular assays, may be useful in hospitalized patients or in patients for whom a confirmed diagnosis will change treatment decisions 4
- Rapid molecular assays are the preferred diagnostic tests because they can be done at the point of care, are highly accurate, and have fast results 4
Treatment Options for Influenza A
- Neuraminidase inhibitors (NAIs) are the treatment of choice for influenza A, due to widespread resistance to the adamantanes 5
- NAIs, such as oseltamivir and zanamivir, are efficacious for the treatment of influenza in ambulatory patients with mild illness, when initiated within 48 hours of symptom onset 5, 6
- Early treatment with NAIs has been shown to reduce otitis media in children and lower respiratory tract complications in adults 5
- Treatment with one of four approved anti-influenza drugs may be considered if the patient presents within 48 hours of symptom onset, with the benefit of treatment being greatest when antiviral therapy is started within 24 hours of symptom onset 4, 7
- No anti-influenza drug has been proven superior, and the decision to use these agents should be based on the age of the patient, antiviral activity, side effect profile, ease of administration, drug interactions, and cost 6
Special Considerations
- In patients at high risk of influenza-related complications, such as young children, the elderly, pregnant and post-partum women, and patients with co-morbidities, NAIs should be initiated as soon as possible, even if the patient presents late 5, 8
- In hospitalized patients, early treatment with NAIs has been associated with reduced mortality, and treatment should not be delayed for the results of diagnostic testing 5, 8
- Corticosteroids should not be used in the treatment of severe influenza, as this has been associated with increased risk of mortality and bacterial superinfection 5