Former US defence secretary Donald Rumsfeld was talking about weapons of mass destruction and the war in Iraq when he referred to “unknown unknowns” in 2002, but he could just as easily have been explaining why drug companies have been able to make money out of the global flu pandemic. Within a few months of his comments, a series of events began to fuel growing international concern about a new pandemic. The mixture of fear and ignorance over its timing, nature, and severity soon sparked an unexpected bonanza for the manufacturers.

Since the emergence of swine flu in Mexico this spring finally triggered the first pandemic in four decades, J P Morgan, the investment bank, estimates that governments have made fresh orders for antiviral drugs of $3bn (£1.8bn; €2bn) and that recent or potential sales of vaccines are $7bn.1 All that despite signs that the virus is proving relatively mild, with potentially less impact than a standard seasonal flu outbreak.

One beneficiary has been Gilead, a fast growing US biotech business that initially developed the antiviral medicine oseltamivir (Tamiflu). In the three months to June this year alone it reported $52m in royalties on its drug. Another who gained was Rumsfeld, Gilead’s former chairman and continuing shareholder, who stressed that he disqualified himself from decisions that could have caused conflicts of interest.2

Roche, the Swiss giant that licensed, commercialised, and manufactured the drug from Gilead, has benefited most of all. In its most recent financial quarter, it generated SFr609m (£350m; €200m; $590m) in sales on the drug. For the full calendar year, it expects that it will contribute SFr2bn to revenues.

Oseltamivir had already become an important product for the company, generating SFr1.6bn …