Comparative and Historical Aspects of the Togaviridae and Flaviviridae

Abstract

Virology is one of the youngest branches of science, having its roots firmly in the study of infectious diseases (Waterson and Wilkinson, 1978). Yellow fever occupies a unique position in the history of virology, and much of our knowledge of the viruses that are the subject of this volume is derived directly or indirectly from research on yellow fever and its causative virus. Although a viral etiology of diseases of plants and domestic animals antedated similar findings concerning diseases that affect man, yellow fever was the first infectious disease of man to be shown to be due to a filterable agent or virus. Yellow fever was also the first viral infection of man to be shown to be transmitted by a blood-sucking arthropod, making yellow fever (YF) virus the archetypal arthropod-borne virus, or ``arbovirus.'' YF virus was the first arbovirus to be successfully cultivated in the laboratory. Field studies on yellow fever resulted in the isolation of many other arboviruses, some of which in time became known as the Group A and Group B arboviruses. A collective name for these viruses was needed, and the term ``togavirus'' (from the Latin toga, a Roman ``mantle'' or ``cloak,'' a reference to the possession of a viral envelope) was adopted as a convenient jargon name. The same root later provided the officially approved family name Togaviridae. This family initially contained only two genera, Alphavirus (the former Group A arboviruses) and Flavivirus (the former Group B arboviruses), named after the type species, YF virus (from the Latin flavus, ``yellow''). Ironically, the very recent elevation of the flaviruses to the level of a family has meant their removal from the family Togaviridae, but this change in no way invalidates the dominant role of YF virus in the history of virology in general and of the Togaviridae in the context of this volume. The stages in the foregoing highly condensed and oversimplified history will now be considered in more detail.