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Flu drug may curb deadly virus
19/07/2005 10:52 - (SA)
Washington - A drug commonly used in the battle against annual influenza strains could help contain bird flu which has killed dozens of people in Asia, US researchers said on Monday.
The drug, which is sold across the counter as Tamiflu "dramatically boosted the survival rate of infected mice", said the researchers.
Millions of chicken and other fowl have died or been destroyed in bird flu outbreaks in several East Asian nations since 2003. The H5N1 strain has killed 38 Vietnamese, 12 Thais and four Cambodians in that time.
Health experts have warned it could become a global pandemic if avian flu develops the ability to spread quickly from person to person.
Researchers at St Jude Children's Research Hospital in Memphis, Tennessee concentrated on Oseltamivir, which is marketed by the Roche company as Tamiflu.
The team gave different daily doses of oseltamivir to 60 mice infected with H5N1 influenza virus for five or eight days and a placebo to 20 others.
Oseltamivir decreases the ability of influenza virus to spread from infected cells to uninfected cells by inhibiting neuraminidase, which is an influenza protein required for the virus to exit infected cells.
Virus continued to grow
None of the mice receiving a placebo survived. Only five of 10 mice given the highest daily dose of oseltamivir for five days survived. Although oseltamivir suppressed the virus in the mice, the virus continued to grow if the drug was stopped after five days.
Mice given the drug for eight days fared better. Survivors included one of 10 mice given the lowest daily dose, six of 10 given the middle-range daily dose, and eight of 10 given the highest daily dose.
The eight-day dose allowed more time for virus levels to fall and less chance for avian flu to rebound after the drug was stopped.
In addition to testing the efficacy of oseltamivir against H5N1 virus in mice, the St Jude researchers compared the virulence of the new virus in Vietnam with a 1997 variant that killed six people in Hong Kong. Researchers found that the 2004 H5N1 virus is much more virulent than the 1997 bird flu.
A longer course of antiviral treatment may be required to conquer the aggressiveness of the new antigenic variant of H5N1 virus, the researchers said.
"We need to know whether antiviral drugs can prevent and treat avian flu, because in the early stages of a global outbreak, most people would be unvaccinated," said Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases.
"If a pandemic occurs, it will take months to manufacture and distribute a vaccine to all who need it."
"The H5N1 avian flu viruses are in a process of rapid evolution. We were surprised at the tenacity of this new variant," said St Jude researcher Elena Govorkova.
- AFP
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