Antivirals effectively curb influenza virus
Two antiviral drugs, oseltamivir and zanamivir, are highly effective when given as a preventive measure to reduce the spread of the influenza virus, according to an analysis of household-based studies by researchers at Fred Hutchinson Cancer Research Center, University of Michigan and University of Virginia, published in the current print edition of the American Journal of Epidemiology. The analysis also suggests that treatment with oseltamivir may reduce the infectiousness of influenza patients, although further studies are needed to provide a definitive conclusion.
"Preventing the spread of influenza within families is an essential part of influenza management, regardless of the strain. This study shows that there is a clear benefit to be gained by giving antivirals to people who have been exposed to the virus to prevent the onset of symptomatic illness," said lead author M. Elizabeth (Betz) Halloran, M.D., D.Sc., a Hutchinson Center-based biostatistician.
"While the efficacy of antivirals to protect against influenza is critical, the effect of these drugs on infectiousness also has important public-health consequences. Further studies to determine antiviral efficacy for reducing infectiousness would therefore be of great value," said Halloran, a member of the Hutchinson Center's Public Health Sciences Division and a professor of biostatistics at the University of Washington School of Public Health and Community Medicine.
The report evaluated four household-based, randomized, placebo-controlled clinical trials, conducted from 2000 to 2004, which were designed to estimate the effect of post-exposure antiviral treatment on preventing influenza within households. Two of the trials were conducted with zanamivir and two with oseltamivir, permitting comparisons to be made between the two. The trials covered a total of 1,475 households. The majority of first household cases (53 percent to 70 percent) had influenza A (H3N2 or H1N1).
The authors reviewed the effects of each antiviral on infectiousness and pathogenicity