Tamiflu is a prescription drug containing the active ingredient oseltamivir that is used to treat influenza virus infections by preventing the virus from spreading. It belongs to a class of antiviral drugs called neuraminidase inhibitors and must be started within two days of flu symptoms appearing. The patent for oseltamivir is held by Gilead Sciences until at least 2016, though it has expired in some countries, and the company has politically well-connected former government officials on its board of directors.