Summary: Dr. Ganem analyses the complex causes of epidemics. He explains how both genetic mutations and changes in the environment and in human social behavior can give rise to new infectious diseases by upsetting a previously established balance between a pathogen and its natural host. He discusses how genetic changes in the structure of the influenza virus have led to epidemics and pandemics. Dr Ganem also shows the impact of weather on a 1993 outbreak of hantavirus, describes the effect of human migratory patterns on the spread of smallpox, and examines what happened when the myxoma virus was introduced in Australia in the 1950s to control the rabbit population.
