I am trying to track down a book of a man who joins a computer company in California who have developed a hard drive which is based upon an altered flu virus. The hard drive grows as it gains more information and the company are about to launch the new computer when the man in the lead role begins to notice changes in the people who work around him. Some die, like the head of sales, but others, the salesman disabled daughter show improvements. It turns out that the individuals have been infected by the virus and it takes over their minds.
As they say in the comments above, this is most likely Human Error by Paul Preuss. (Review here).
The infection in the book is a polio virus, not a flu virus, but the effects of it are as described above. The review states:
But so powerful is Epicell that soon it's producing original work. Meanwhile, however, those who have intimately handled Epicell develop mysterious ""colds"" (readers will guess what's going on long before the characters catch on). Yes, they've been infected with Epicell--which proceeds to develop inside the victims' brains. The first sufferers, unable to handle the human/computer interface, die; later, though, others survive to manifest such strange and highly beneficial new abilities as instant computing, perfect memory and coordination, heightened emotional sensitivity, and more.