Ecological aspects of influenza A viruses in animals and their relationship to human influenza: A review

Abstract

It is a reflection of the continuing importance of influenza that it has been termed 'the last great plaque of man'. In many respects influenza in man is unique in its epidemiology, most particularly in that at intervals as short as 10 years or as long as 40 a 'new' virus emerges which results in worldwide infections of a large proportion of the human population. Such pandemics may have an enormous impact on society in terms of mortality, morbidity and economic factors. Because of these effects there are detailed accounts of recognizable influenza pandemics which data back many centuries. Possibly the most devastating influenza pandemic recorded occurred in 1918. It has been estimated that during this pandemic between 20 and 40 million deaths occurred throughout the world and that in a developed country, such as the USA, about 0.5% of the population died.