what kinds of flu are fatal
1 Avian Flu: Some types of Avian Flu viruses (H5N1, H7N7) are associated with severe and fatal disease. 2  The viruses do not usually infect humans, however, confirmed cases of human infection have been reported since 1997, especially in Asia.ype C has been found in humans, pigs, and dogs and causes either a very mild illness, or has no symptoms at all. It does not cause epidemics and does not have the severe public health impact that influenza types A and B do. The typical incubation period for influenza is 1 to 4 days, with an average of 2 days.