Tamiflu may not be as effective as hoped against bird flu

Dec 22 2005

The stockpiles of bird flu drug Tamiflu, accumulated by governments around the world as the first line of defense against a flu pandemic, may prove to be useless.

At present Tamiflu appears to be the only drug available against the H5N1 avian flu virus, but now some experts are questioning the drugs' use for many of those infected and believe it may even worsen a pandemic.

According to a study by Dr. Menno de Jong and colleagues of the Oxford University Clinical Research Unit at the Hospital for Tropical Diseases in Ho Chi Minh City, four of eight patients treated in Vietnam for bird flu infections died despite the use of Tamiflu.

Of the 13 Vietnamese patients infected with avian flu who were treated with the antiviral drug, Tamiflu, tests showed that in two of the patients, the virus had become resistant to Tamiflu, and in one of those patients the drug was used very early on, as recommended.

Some experts have described the findings as frightening and researchers are warning against an indiscriminate use of the drug in the event of a pandemic.

They say that could very well fuel the growth of a resistant virus strain, and trigger a second wave of infection against which there would be no defense.

According to Professor Anne Moscona of Cornell University, it is becoming clear that to treat avian flu with neuraminidase inhibitors such as Tamiflu, higher doses and a longer course of treatment is needed for them to work.

She and other experts agree that such drugs must be preserved carefully and used properly.

They do say however that the report concerned only a few people and stressed that more study is needed.

To date the H5N1 virus has infected a total of 138 people in Asia and killed 71 people in Indonesia, Thailand, Vietnam, China and Cambodia since 2003.

It is feared the virus could mutate and be transmitted amongst humans.

At present bird flu is difficult to catch and usually results from direct contact with sick birds.

Professor Moscona says the Vietnamese cases raise the worrying prospect that even with therapeutic doses, a resistance to Tamiflu may emerge.