Widespread Tamiflu Usage Against Avian Flu Could Backfire

Via RockyMountainNews -

Avian flu could gain a huge toehold in the United States if public health officials make the mistake of distributing Tamiflu to everyone, a new study suggests.

Fewer than 400 people have had a documented case of avian flu, and some 200 have died.
But epidemiologists worry that if the virus mutates to the point that people can get it simply by being near birds or other humans, it could wipe out hundreds of millions of people worldwide.

Researchers from the University of Colorado and Ohio State University point to what happened with a group of antiviral drugs known as adamantanes.

Farmers in China started feeding the drugs to their chickens as a way of keeping the poultry safe from avian flu.

But in the process, the avian virus appears to have found a way to be resistant to the drug.

Consequently, 30 percent of the avian flu samples recently analyzed by the study authors proved resistant to the adamantane drugs.

Only about 1 percent of the avian flu samples are resistant to a second class of drugs that include oseltamivir, marketed as Tamiflu.

But tens of millions of Tamiflu doses are stockpiled in local, county, state and federal storage areas, awaiting the day when an American gets the virus.

The same thing could happen, though, if Tamiflu is distributed like chicken feed, said Andrew Hill, a CU-Boulder doctoral student who was the lead author of the study that appears online in the journal Infection, Genetics and Evolution.

"As these adamantanes have gotten into non-human vectors like birds, the positive selection for resistance to avian flu is rising," Hill said. "If Tamiflu is ever used in the manner of adamantanes, we could conceivably see a similar resistance developing."

The paper suggests that widespread use of antivirals can speed the rate at which the virus grows resistant to the drugs.

Terry Hurley, spokesman for Roche Pharmaceuticals, which makes Tamiflu, said company officials haven't yet seen the study.

"But there is no data that indicates increased Tamiflu usage leads to resistance. In fact, the countries that use Tamiflu the most, like Japan, have the lowest resistance rates," he said.

He said Tamiflu has a completely different mechanism of action than the adamantanes. He added that Tamiflu is not given to animals.