What are WHO treatment guidelines for H1N1 influenza (swine flu)?

Updated: Apr 09, 2019
  • Author: Michael Stuart Bronze, MD; Chief Editor: Russell W Steele, MD  more...
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WHO guidelines recommend treating serious cases immediately. [27] The guidelines represent an international panel of experts who reviewed all available studies regarding antiviral agents (with emphasis on oseltamivir and zanamivir). Evidence indicates that oseltamivir, when properly prescribed, significantly decreases risk of pneumonia (a leading cause of death for both pandemic and seasonal influenza) and the need for hospitalization.

In the 2009 H1N1 pandemic, oseltamivir-resistant strains were observed in a small number of patients. Most oseltamivir resistance occurred in severely immunocompromised patients with prior exposure to oseltamivir. [28]

For patients who initially present with severe illness or whose condition begins to deteriorate, initiate oseltamivir as soon as possible. For patients with severe or deteriorating illness, treatment should be provided even if started later. Where oseltamivir is unavailable or cannot be used for any reason, zanamivir may be given. This recommendation applies to all patient groups, including pregnant women, and all age groups, including young children and infants.

For patients with underlying medical conditions that increase the risk of more severe disease, WHO recommends treatment with either oseltamivir or zanamivir. These patients should also receive treatment as soon as possible after symptom onset, without waiting for the results of laboratory tests. Pregnant women are included among groups at increased risk, and WHO recommends that pregnant women receive antiviral treatment as soon as possible after symptom onset.

At the same time, the presence of underlying medical conditions will not reliably predict all or even most cases of severe illness. Worldwide, around 40% of severe cases are now occurring in previously healthy children and adults, usually younger than 50 years. Some of these patients experience a sudden and very rapid deterioration in their clinical condition, usually on day 5 or 6 following the onset of symptoms.

Clinical deterioration is characterized by primary viral pneumonia, which destroys the lung tissue and does not respond to antibiotics, and the failure of multiple organs, including the heart, kidneys, and liver. These patients require management in intensive care units using therapies in addition to antivirals.

Peramivir, an investigational, intravenous neuraminidase inhibitor in Phase 3 clinical trials, has been used successfully in adults and children under an emergency investigational new drug program in the United States. It was well tolerated and associated with recovery in the majority of patients hospitalized with severe H1N1 infection. [29]

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