Tamiflu, a flu drug manufactured by Swiss company Roche, can prevent mortality in mammals infected with the H5N1 bird flu virus, according US researchers who conducted a study with ferrets.

However, more studies are needed to determine the optimal dose and duration of treatment, the research group announced on Wednesday at a two-day bird flu conference organized by The Lancet medical journal in Singapore.

The experiment also confirmed the benefits of Tamiflu - known generically as oseltamivir - when given early.

The World Health Organisation has recommended Tamiflu as the best available line of defence against H5N1 and governments in many countries have already begun to stockpile the drug in a global effort to combat a possible pandemic.

Although the disease is still confined largely to birds, it has killed 113 people of 205 infections reported since late 2003 and experts fear it will trigger the next pandemic once it learns how to transmit efficiently among people. As of now, it does not pass easily among people and most human victims contracted the virus directly from sick birds.

In the study, researchers at the St. Jude Children’s Research Hospital in Memphis, Tennessee, infected ferrets with the most pathogenic strain of the H5N1 virus, which has been circulating in Vietnam since 2004.

Like humans, ferrets are very susceptible to influenza and develop similar symptoms, such as diarrhoea, fever and weight loss.

BENEFITS

According to one of the researchers, Elena Govorkova, all the ferrets that were given 5 mg/kg oseltamivir each day survived, while other ferrets in a control group given no drugs all died.

The lungs, intestines, brains and spleens of those that died were also found infected with the virus.

The group that was given the drug - four hours after infection - had virus present only in the brains.

To make the test more realistic, the researchers did a parallel experiment, administering the drug 24 hours after infection and obtained similar results. Ferrets given the drugs all survived while those given no medication all died.

The control group was also found with virus-ridden organs, while those given the drug had virus only in the brains.

“Oseltamivir is good but we still need to know more about optimal treatment schedule, like dosage, duration and how long we can delay the treatment after infection,” Govorkova said in an interview with Reuters.

The results of the ferret study, which was conducted in January, follows recent reports saying there was no hard evidence backing the efficacy of Tamiflu in fighting the virus in people.