Mutation of virus similar to swine flu resistant to drugs

DICK AHLSTROM Science Editor

AN INFLUENZA virus similar to swine flu has mutated and strains are now emerging globally that are resistant to the frontline drug treatment Tamiflu.

Similar resistance has also been seen in patients with swine flu where resistance to antiviral treatment can emerge in less than two weeks.

The antiviral drugs Tamiflu (oseltamivir) and Relenza (zanamivir) are a key part of the Government’s response should a swine flu pandemic emerge here. Now scientists in California have shown how the ordinary or “seasonal” form of the H1N1 flu can become resistant to antivirals.

The group, led by Nobel Prize winner Prof David Baltimore of the California Institute of Technology, showed how a number of mutations have helped the seasonal H1N1 to survive treatment with these drugs. They publish their findings this morning in the journal Science .

The key mutation, known as H274Y, is not new and has been known for a decade, Prof Baltimore said. Viral strains with it are able to survive treatment with Tamiflu, but having the mutation also meant they replicated poorly and were not easily transmitted, which meant they “were not of great clinical significance”.

But during the 2007-2008 flu season, forms of H1N1 carrying the the mutation began cropping up all over the world, showing powerful drug resistance but also the ability to spread across a population, the researchers said.

By the following season, virtually all seasonal H1N1 had become resistant to Tamiflu.