The avian influenza (bird flu) scare is very current in the media Different H and N types of influenza viruses infect birds, mammals and humans. Flu is very common among birds, but is almost always asymptomatic or only mildly pathogenic. Normally, avian flu does not infect humans. Since 1996, a new virus, designated 'highly pathogenic avian influenza' (HPAI) H5N1, has caused outbreaks (epizootics) of severe illness with high mortality in chicken and duck farms in many East Asian countries. It has caused human illness in about 140 individuals, with 50 per cent mortality Millions of poultry and ducks have been killed to contain the epizootics; yet the illness continues to occur and has now spread to Eastern Europe. Although H5N1 does not transmit between persons, flu viruses are notorious for their genotypic and phenotypic plasticity and we fear that there may be eventual adaptation to human hosts and a devastating epidemic. The world has to balance anxiety and hype on the one side and public health preparedness on the other.