Questions and answers related to H5N1 Bird Flu (Avian Flu). It is an extremely virulent influenza virus that can infect birds, occasionally pigs, rarely infections in other animals, and very rarely humans. Fortunately, it does not spread very easily, and only extremely rare human to human transmissions have been known to occur. No instance of the virus spreading beyond a first generation of close human contacts has been reported. It does, however, have a very high mortality rate in animals and in humans (60% death rate in humans).