Adults with influenza infections serious enough to require hospitalization are much less likely to die from the disease if they are given antiviral medications, according to a new study published in the December 15 issue of Clinical Infectious Diseases. While previous clinical trials have shown the antiviral benefit in a relatively young, healthy adult population if they were treated within 48 hours of the onset of flu symptoms, this study showed a significant benefit to an older population even when given antivirals three or four days after the appearance of flu symptoms.
Influenza is a disease contracted by between 5 percent and 20 percent of the US population each year. Annually, more than 200,000 Americans are hospitalized with the flu and about 36,000 die from the disease. Older people and young children are at higher risk for serious flu complications.
"Influenza causing hospital admission is more common than most people think. We will save lives if we recognize and appropriately treat influenza in patients being admitted to the hospital," said lead author Allison McGeer, MD.
This study was conducted by Dr. McGeer and colleagues from the Mount Sinai Hospital, the University of Toronto, and the Toronto Invasive Bacterial Diseases Network. They analyzed data from 327 adults who were hospitalized for influenza between January 2005 and May 2006. Approximately one-third of the patients received antiviral therapy. Treatment with antivirals reduced the risk of death by nearly 80 percent.
It is notable that many of the patients who received antiviral medication three or four days after the appearance of flu symptoms seemingly benefited. Previous research has shown that in otherwise healthy adults, influenza virus is cleared quickly by the body's immune response and antiviral therapy given more than 48 hours after the onset of symptoms is unhelpful. The authors note that some of their patients may have been immunocompromised for non-flu related reasons and might therefore retain the virus longer than healthy patients. Another possibility is that patients who require hospital admission for influenza are a small subgroup of the people who get infected. These patients may have trouble controlling the virus and thus develop more serious, more prolonged illness.
This research supports the use of antiviral medications to treat people hospitalized with influenza. "Antiviral medications are very safe, have no significant drug interactions, and relatively few side effects," said Dr. McGeer. "You don't, however, want to take them if you don't need them. As with antibiotics, there is a risk of selection for antiviral resistance and it is important to use the medications only where there is a clear benefit."
The authors do not want to diminish the value of influenza vaccines. "There is a great deal of data proving that vaccine is effective and cost-effective," added Dr. McGeer. "Our data simply say that despite the substantial reductions in death and illness associated with vaccine use, considerable morbidity and mortality due to influenza remain. We need--and people are working on--better vaccines; until we get them, we can help people by diagnosing and treating disease."
This study was funded by a grant from Hoffmann-La Roche Ltd., manufacturer of the antiviral drug oseltamivir, which was used in the study. Hoffman-La Roche had no role in the design or conduct of the study; in the collection, management, analysis or interpretation of the data; or in the preparation, review or approval of the manuscript. Full disclosures are in the manuscript.
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