By Richard Knox

Sorry, but here's another reason to worry about swine flu.

It's the possibility that the newly discovered virus will become resistant to the only two drugs now available to treat it -- Tamiflu and Relenza.

It's not an idle threat. Most of the ordinary flu viruses circulating this year are resistant to Tamiflu. Those resistant viruses are a type called H1N1. That's the same family as the swine flu virus, although the new bug is genetically different.

So it's not far-fetched that swine flu could also acquire the genes that confer Tamiflu resistance. That could be disastrous if swine flu goes pandemic.

But there may be a way to hedge against that problem. Researchers say doctors should hold off using Tamiflu at first and use Relenza instead. Using computer models, the researchers calculate that Tamiflu resistance could be substantially delayed if only 1 percent of the population were treated with Relenza first.

That would preserve supplies of Tamiflu, the mainstay drug in pandemic flu stockpiles.

Delaying drug resistance could ease the burden on the medical system from treating people with severe flu complications. Meanwhile, more people could get vaccinated against swine flu, preventing them from getting sick in the first place.

"The proposal would be to take our limited Relenza stockpile and use it as much as possible at the beginning of a swine flu outbreak," says Marc Lipsitch of the Harvard School of Public Health. He's a coauthor of a report in the Public Library of Science/Medicine. It was funded by the Hong Kong government and the U.S. National Institutes of Health.

Lipsitch says using Relenza to delay Tamiflu resistance would also prevent the spread of resistant flu viruses.

Relenza can't be used for everybody. Tamiflu is a pill, but Relenza has to be inhaled. It's not approved for young children or people with asthma.

categories: The disease

7:25 - May 1, 2009

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