re: bad news relenza oseltamivir-resistant h5n1 vi Saturday, October 15, 2005 Page A24
Reuters News Service
WASHINGTON -- The feared avian-influenza virus is showing signs it can evade the drug considered the first line of defence against bird flu, U.S. researchers said yesterday.
They found so-called resistant strains in a Vietnamese girl who recovered from a bird-flu infection after being treated with Tamiflu. They also found evidence she was directly infected by her brother, and not by chickens; a rare case of human-to-human transmission of the virus.
When bacteria and viruses develop resistance to a drug, it means higher doses of the drug are needed to eradicate or control an infection. Ultimately, it means the drug will stop working.
This has happened with many antibiotics, starting with penicillin, and is common among AIDS drugs.
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The findings illustrate the need to locate and use other drugs to treat influenza and to work quickly to develop a vaccine, the researchers said.
"I don't think we need to panic based on this finding," Professor Yoshihiro Kawaoka of the University of Wisconsin-Madison, who led the study, said in a telephone interview.
But the report, to be published in the journal Nature next week, is bad news for doctors around the world who already have precious little in the arsenal against bird flu, should it become a human disease.
"This is the first line of defence," Prof. Kawaoka said. "It is the drug many countries are stockpiling, and the plan is to rely heavily on it."
The H5N1 strain of avian influenza is considered by health experts to be the single biggest disease threat to the world. Since surfacing in Hong Kong in 1997, it has spread in flocks of poultry across Asia and is now in Turkey.
It does not yet move easily from birds to humans, but it has infected 117 people in four Asian countries and has killed 60 of them, according to the World Health Organization.
British virology expert John Oxford said cases in Thailand have demonstrated that the basic virus can pass between humans, and predicted that similar small clusters of cases would be seen again, the BBC reported.
WHO believes the virus will eventually acquire the ability to move easily from human to human and that when it does, it will cause a pandemic that will sweep the world in weeks or months and kill millions if not tens of millions of people.
Countries are stockpiling supplies of Tamiflu, an antiviral drug known generically as oseltamivir phosphate. They are to a lesser degree buying up supplies of Relenza, known generically as zanamivir. This drug is also effective against avian flu, but is administered through the nose and thus is less desirable than the Tamiflu pill.
Prof. Kawaoka, who also works at the University of Tokyo, teamed up with colleagues in Japan and Vietnam to analyze samples of virus taken from a 14-year-old Vietnamese girl, called Patient 1, who recovered from an H5N1 infection last March.
"Patient 1 had not had any known direct contact with poultry, but had cared for her 21-year-old brother [Patient 2] while he had a documented H5N1 virus infection," Prof. Kawaoka and colleagues wrote in their report. The girl had been given Tamiflu three days before she became ill, and then was treated with the drug when it failed to prevent her infection.
Prof. Kawaoka's team found several types of H5N1 virus in the girl's sample, some of which had developed genetic mutations to make Tamiflu ineffective against it.
"Although our findings are based on a virus from only a single patient, they raise the possibility that it might be useful to stockpile zanamivir as well as oseltamivir [phosphate] in the event of an H5N1 influenza pandemic," the researchers wrote.
Meanwhile, the European Union executive said yesterday in Brussels that European governments must define the areas most at risk from bird flu, so that wild birds can be separated from poultry to minimize the risk of the disease spreading.
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