Influenza, or the flu, is a common infectious disease, which can be deadly to individuals with compromised immune systems (the very young, the very old, and those with conditions such as AIDS or Cancer). However, occasionally particularly virulent strains of influenza break out that can be threatening on a much larger scale -- such as the flu epidemic of 1918 and, more recently, concerns that H5N1 "Bird Flu" or H1N1 "Swine Flu" could mutate into a highly-infectious and deadly virus. A number of pharmaceutical companies make treatments for the flu and benefit from the fear of a flu outbreak.
In April 2009, a novel flu virus, known as "Swine Flu" because it was believed to have originated in pigs, started infecting humans. By April 28th, there were 1,300 confirmed cases of the flu, known by its scientific designation H1N1, in Mexico, and a handful in the U.S. and other parts of the world.
According to preliminary test done by the US Center for Disease Control, Roche Pharmaceuticals (RHHBY)'s Tamiflu and GlaxoSmithKline (GSK)'s Relenza are active against H1N1, although many older drugs are not.