Drug Blocks Flu Spread Up to 81%

The antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) help reduce the spread of seasonal flu within families, a new study suggests. Researchers from Seattle's Fred Hutchinson Cancer Research Center, the University of Michigan and the University of Virginia also suggested that oseltamivir may reduce the infectiousness of flu patients, but further research is needed to confirm this.

The Study

The authors reviewed four studies of 1,475 households where a family member had the flu. The two studies that looked at zanamivir found that the drug's effectiveness in reducing pathogenicity (the ability of the flu virus to cause overt disease) was 52% and 56%. In the two studies on oseltamivir, it was 56% and 79%.

The study also found that use of either drug reduced by 75% to 81% the chance that a person exposed to a flu virus would become ill.

"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 Dr. M. Elizabeth Halloran, a Fred Hutchinson Cancer Research 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, who is also a professor of biostatistics at the University of Washington School of Public Health and Community Medicine in Seattle.