When the H5N1 highly pathogenic avian influenza virus was discovered on a poultry farm in Asia in 1996, there was little indication that it would become so widespread and so destructive. Within 30 years, it reached every continental region except Oceania, infecting more than 400 million poultry, tens of thousands of elephant seals and sea lions, about 1,000 people and many other mammals and wild birds.