July 19, 2005

Animal tests show Tamiflu suppresses pathogenic bird flu

Tamiflu, an antiviral drug against bird flu strains, has been shown to suppress the pathogenic bird flu virus in mice, US scientists said on Jul 18.

This study conducted by researchers at St. Jude Children's Research Hospital found that the oseltamivir could dramatically boost the survival rate of infected mice.

Researchers tested the drug for an extended eight-day period although the recommended human dose is for five days. For mice administered only during the recommended period, researchers found that the virus was suppressed during the five days the drug was used, but continued to grow after that.

Mice given the drug for eight days fared better, with one mouse given the lowest dose of the drug surviving too. Researchers explained that the eight-day dose allowed more time for virus levels to fall and less chance for the flu to rebound.

Researchers also found that the 2004 H5N1 virus currently circulating in Vietnam is much more virulent than its 1997 predecessor found in Hong Kong. Thus, researchers suggested that a longer course of antiviral treatment might be required to overcome the current H5N1 virus.

There are already plans to do additional studies on small animals in which the avian flu infection closely resembles that in humans, to see if using higher doses of the oseltamivir for a longer period of time can prevent the H5N1 virus from spreading from the lungs to the brain.