Flu breakthrough Australian researchers have helped develop a new class of influenza drug that tricks the virus by using its own mechanism of infection.

So far, the drug has been used to successfully treat mice infected with lethal strains of influenza - including resistant strains of the virus.

The international team of researchers, which includes Australian scientists from CSIRO, believe the virus may not be able to develop resistance to this new type of drug because it stops a process that is common to all strains of flu.

The flu virus has two "spikes" or proteins that it uses in the infection process, explains McKimm-Breschkin, who was part of the team that developed the first flu drug Relenza.

The first "spike", hemagglutinin (HA), binds the virus to a healthy cell through sugars on the cell surface. The virus is then "swallowed" by the cell where it multiplies.

"One [virus] goes in and between 100 and 1000 come out 12 hours later," McKimm-Breschkin says.

The virus then uses a second "spike", neuraminidase (NA), to sever its connection to the sugar - and therefore the cell - "allowing the virus progeny to spread to uninfected cells", the research shows.

McKimm-Breschkin says the new drug stops this latter process by blocking the "mouth" of the neuraminidase so the virus remains attached to the cell and cannot spread.

"We have found [the flu's] Achilles heel," she says.

Understanding exactly how flu viruses become resistant to drugs has helped the researchers to design a better flu drug, says McKimm-Breschkin.

As the site where the drug binds is found in all flu strains, the new drug is expected to be effective even against future flu strain, she says

Millions affected

The World Health Organization estimates influenza affects three to five million people globally each year, causing 250,000 to 500,000 deaths.

McKimm-Breschkin says it is important to "stay a step ahead" of the virus by developing new drugs to combat its spread.

"With millions of poultry currently infected with 'bird flu' globally, there are still concerns about its adaptation and potential to spread among humans, causing the next pandemic," she says.

She says in 2008 a seasonal flu developed a random mutation in Norway making it resistant to Tamiflu.