In a bird flu pandemic tamiflu may not be as effective as authorities hope.

Many countries like the USA are stockpiling tamiflu in preparation for a bird flu pandemic.

Members of the public are buying up tamiflu for their own personal bird flu protection.

But until the bird flu mutates to a human to human virus we can't be certain that tamiflu will be effective against the bird flu virus.

And the latest signs are not good...

In an unsettling development for health authorities tamilflu resistant strains of the bird flu are appearing.

A vietnamese girl diagnosed with bird flu with a tamiflu resistant strain of bird flu.

Fortunately she survived after being treated with Relenza - another antiviral drug.

In China the bird flu strain H5N1 is showing around 70% resistance to adamantane drugs like Tamiflu.

William Chui from the Queen Mary Hospital in Hong Kong said viral resistance to tamiflu was growing in Japan where doctors commonly prescribe the drug for influenza.

It's also important to note that Tamiflu and other anti viral drugs don't stop the bird flu from entering your body - they fight the virus once it is already inside your body.

Tamiflu works by stopping the virus from bursting out of infected cells in your body.

It does this by inhibiting an enzyme called neuraminidase on the surface of the virus cells.

This can help stop viruses like the bird flu infecting other cells in your body and also possibly reduce the chance that you'll infect other people.

To be effective you need to take tamiflu within 48 hours of becoming ill.

But if a bird flu strain is resistant to the drug then tamiflu may not be the answer to a bird flu pandemic.

It pays to be prepared and the first preparation is paying attention to personal hygiene.

Around 90% of respiratory viruses like the bird flu, the common cold and influenza that enter our bodies get there when we touch the mucous membranes of our eyes and nose with our fingernails.

So hand washing really is the first line of defense against a bird flu pandemic - not tamiflu.

But washing your hands is more complex than it might seem on the surface.

You need to use the right kinds of soap and if you can't use soap there's only one alternative that's proven by the USA Centers Of Disease Control to be effective and it's NOT an antibacterial solution.