The Swiss drugs company Roche has agreed to meet four American firms who say they can make Tamiflu, which is widely seen as the most effective treatment for the bird flu virus in humans. But it could still be hard to make enough Tamiflu to meet demand. This report from Mark Gregory:

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Shortage of star anise would have been a major constraint on increasing production of Tamiflu, except that a few months ago a way was found of making shikimic acid artificially. Roche now derives some of the raw material it needs from fermenting e-coli bacteria. Other drug companies can copy this - but it won't be easy and it won't be quick. Every batch of Tamiflu takes a year to make - and at one of the ten stages the material is highly explosive.

Roche now says its willing to let other drug companies manufacture Tamiflu, but even if this does happen soon it will certainly be months, and possibly years, before stocks are big enough to meet potential demand in the event of a bird flu pandemic in humans.

Mark Gregory, BBC business reporter

Listen to the words

extracted from
taken from

harvested
taken from the ground

Shortage
A period when there isn't enough of something

a major constraint
a big restriction

artificially
through a man-made method, not through nature

derives
obtains, gets

batch
quantity of something made at a particular time

stocks
supplies

potential demand
possible need

in the event of a bird flu pandemic in humans
if many people around the world become ill with the human form of the bird flu virus

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