The importance of viral disease, although estimated with difficulty, seems very large in human pathology. Viruses appear to be involved in most of respiratory disease. Moreover, in tropical countries, measles and viral diarrhoeas (mainly rotaviruses) are fatal for many children. But smallpox eradication must be considered as the most important fact which occurred in the field during the last five years, and the consequences of this new situation are discussed. Finally, beyond the recent question of african viral haemorrhagic fevers, one must take in account the increasing prevalence of several arboviruses, specially dengue in southeast Asia, which is one of the first causes of paediatric mortality in urban environment.