Avian influenza is the most serious known health threat facing the world. An infectious disease of birds caused by type A strains of the influenzavirus. The virus mainly affects the birds but can also infect humans. Among the few subtypes that have infected humans, H5N1 is the most dangerous one. The virus has high mutation rate (as all RNA viruses) and thus can escape immune defense. Conditions for transmission and jumping species barriers are ideal where poultry, ducks, pigs, and humans live in crowded conditions. Our great concern is human- to- human transmission which poses an imminent threat of a global pandemic. Proper acurrate and early diagnosis will be helpful. Prevention and control measures will help greatly in overcoming this coming threat