Antiviral drugs used to treat the human flu aren't likely to hold off a pandemic outbreak of bird flu because of the virus' ability to mutate, new research suggests.
University of Colorado at Boulder scientists analyzed nearly 700 avian flu genome sequences from bird, cat and human hosts, discovering about one-third of them had mutations to resist the effects of popular flu drugs.
The research was focused on a class of antiviral drugs no longer used in the United States because they have lost their effectiveness. But the study also suggests that more modern antiviral drugs — including Tamiflu, stockpiled by governments, businesses and individuals in case of a flu pandemic — could eventually lose their potency after widespread use.
Drugs spur virus changes
Fewer than 1 percent of the samples in the study were resistant to Tamiflu. Still, the study serves as a warning to anyone planning to rely on antiviral drugs during a flu pandemic.
"The main significance is that human antivirals can have very powerful impacts on a nonhuman disease," said Andrew Hill, lead author of the research, published in the journal Infection, Genetics and Evolution. "Human drugs are affecting the ways that this virus is evolving."
The increased resistance to the drugs potentially is linked to Chinese farmers adding it to their chicken feed.
Exposing birds to the drugs causes resistant strains of the avian flu to proliferate, said study co-author Robert Guralnick.
Chinese fear one sick bird
Chinese farmers give chickens the drugs because one sick bird can mean all the stock is killed, Guralnick said.
Internet sales of Tamiflu skyrocketed in 2005, at the height of the avian flu scare.
Fewer than 400 people worldwide have contracted the bird flu, and experts believe that, at least for now, the flu is transmitted to humans only through diseased birds.
The death rate among humans is above 60 percent.
Avian flu has spread from Asia into Africa and Western Europe.
Jennifer Brown: 303-954-1593 or firstname.lastname@example.org