Alphaviruses: Population genetics and determinants of emergence

Abstract

Alphaviruses are responsible for several medically important emerging diseases and are also significant veterinary pathogens. Due to the aerosol infectivity of some alphaviruses and their ability to cause severe, sometimes fatal neurologic diseases, they are also of biodefense importance. This review discusses the ecology, epidemiology and molecular virology of the alphaviruses, then focuses on three of the most important members of the genus: Venezuelan and eastern equine encephalitis and chikungunya viruses, with emphasis on their genetics and emergence mechanisms, and how current knowledge as well as gaps influence our ability to detect and determine the source of both natural outbreaks and potential use for bioterrorism. This article is one of a series in Antiviral Research on the genetic diversity of emerging viruses.

Encephalitic Arboviruses: Emergence, Clinical Presentation, and Neuropathogenesis

“…The encephalitic members of the Togaviridae family alphaviruses (new-world group) consist of the Eastern, Western, and Venezuelan equine encephalitic viruses (EEEV, WEEV, and VEEV, respectively). The VEEV complex comprises 14 subtypes and varieties and includes 7 different virus species, while EEEV includes North and South American variants, with 4 major lineages [1]. Chickungunya virus (CHIKV) is another member of the Togaviridae family (old-world group) and Semiliki Forest virus complex that can cause central nervous system (CNS) disease [2].…”

A real-time RT-PCR for rapid detection and quantification of mosquito-borne alphaviruses

“…These viruses have been introduced into new areas as a consequence of the rapid expansion of international travel. Furthermore, ecological disturbances produced by man have resulted in an imbalance of sylvatic cycles bringing vectors and consequently, the alphaviruses closer to urban areas [36]. Consequentially, the wide variety of reservoirs coupled with the spreading of both vectors and viruses through international travel has led to the global distribution of these viruses.…”

“…Consequentially, the wide variety of reservoirs coupled with the spreading of both vectors and viruses through international travel has led to the global distribution of these viruses. Moreover, the lack of effective antiviral treatments or human vaccines have enabled alphaviruses to become a threat that can result in explosive epidemics, as recently described for CHIKV in the Americas [5,20,36].…”

“…In 2014, Brazil suffered two introductions of CHIKV, one by the Asian strain in the North and another by the East, Central and South African strain in the Northeast [5]. Additionally, numerous alphaviruses, such as the Eastern equine encephalitis (EEEV), Western Equine Encephalitis (WEEV) and Venezuelan Equine encephalitis have produced many epizootics in ungulates and epidemics in human populations of the Americas [13,36]. EEEV, VEEV and WEEV are known to cause human and equine encephalomyelitis with high fatality rates and the development of neurological sequelae in survivors [38].…”

“…The most important vectors involved in the transmission of these viruses are Culex and Aedes mosquitoes, and their vertebrate hosts are mammals, birds, and eventually, humans [36].…”