A University of Wisconsin researcher reported Friday a case of the avian flu in a human has gained resistance to a drug designed to treat the influenza virus, raising questions as to how health officials would combat a possible avian flu pandemic.
Avian influenza has drawn worldwide attention over the past two years, and the World Health Organization (WHO) has confirmed 117 human cases of the bird flu, known as H5N1. All cases have been found in Southeast Asia, though health officials routinely test patients in the United States who are suspected of having the virus.
WHO recommended health-care facilities stock up on the anti-viral drug oseltamivir — commonly known by its trade name, Tamiflu — earlier this year. Though Tamiflu can be used to treat all forms of influenza, officials intended to use the drug in the case of an avian flu pandemic to stave off the spread of the flu while a vaccine could be developed.
However, Yoshihiro Kawaoka, a researcher holding a joint appointment at UW School of Veterinary Medicine and the University of Tokyo, announced a Vietnamese girl given a "prophylactic dose" of Tamiflu after showing "mild" flu symptoms did not respond to the treatment.
"This is the first line of defense," Kawaoka said of Tamiflu in a release. "It is the drug many countries are stockpiling, and the plan is to rely heavily on it."
Though the resistance has only been found in one person, Kawaoka said there is no question there will be others.
Kawaoka added the federal government plans to spend billions of dollars to boost national inventory of Tamiflu and has already obtained more than 12 million courses of the drug.
Tamiflu curbs the spread of the flu and can be used to reduce symptoms in people who have the flu, but it is not a replacement for an avian flu vaccine, which could take months to develop if the flu becomes pandemic.
Despite this finding, UW University Health Services epidemiologist Craig Roberts said hype surrounding the bird flu and the recent announcement of one case of resistance to Tamiflu are inflated.
"Resistance doesn't happen all at once," Roberts said. "So in this one particular case it was resistant, but that doesn't mean all [avian flu cases in humans] will be resistant."
Roberts said historically, there have been occurrences of other strains of influenza developing resistance to anti-viral treatments.
The avian flu is far from being pandemic, Roberts said, noting the virus must be easily transmissible from human-to-human, there must be no existing immunity to the bird flu in the human population and the virus must cause severe illness in humans in order to be considered "pandemic."
Thus far, two of the three criteria have been met, but the virus is not communicable among humans; it can only be spread from bird to bird, or bird to human.
"The people who have [avian flu] have acquired it, presumably, from birds," Roberts said, adding the virus must mutate in order to pass from human to human.
There are two other anti-viral drugs available to treat the flu, Roberts said, but neither is as effective or easy to dispense as Tamiflu. Adamantine and zanamivir were considered as potential treatments for the bird flu; however, this flu is resistant to adamantine, and zanamivir — whose trade name is Relenza — is difficult to administer.
"The worst-case scenario is the resistance [to Tamiflu] could spread," Roberts said. "And then [in the case of pandemic flu] there would be no anti-viral drugs that would work correctly against the avian flu virus."
Kawaoka's findings will be published in this week's edition of Nature.
