US health officials today said they have purchased more than 14 million courses of antiviral treatments from Roche Holding and GlaxoSmithKline in preparation for a possible avian flu pandemic among humans.
The department of health and human services ordered 12.4 million courses of Roche's Tamiflu and 1.75 million courses of Glaxo's Relenza, it said in a statement.
The agency has already purchased 5.5 million courses of antiviral drugs for its government stockpile, it added.
Roche, in a separate statement, said it had filled all previous US orders.
Concerns the H5N1 avian flu strain could mutate and easily move from person to person, possibly causing a global pandemic, have increased demand for Tamiflu, also known by the generic name oseltamivir.
Other countries and some consumers also have rushed to stockpile the drugs in the hopes that they will prevent infection or at least relieve symptoms from the so-called bird flu.
Under the Bush administration's plan, the agency aims to have enough medication to treat 25 per cent of the US population in the event of an outbreak.
Last month, Roche officials said federal officials had agreed to buy 46 million rounds of its treatment.
Experts consider Tamiflu their main choice, but its effects against the virus are not well known, and it must be given early on in the infection.
Relenza, invented by Australia's Biota Holdings and also known as zanamivir, is considered equally effective but must be inhaled and may worsen asthma and related conditions.
So far, 92 people have died worldwide, mainly in Asia, from avian flu since it emerged in late 2003, according to the World Health Organisation.