Alphaviruses in Latin America and the Introduction of Chikungunya Virus

Abstract

Alphaviruses are enveloped, single-stranded, plus-strand RNA viruses belonging to the Togaviridae family. These are zoonotics and arthropod-borne viruses (mainly mosquitoes) that are distributed nearly worldwide. Many of the New World alphaviruses occur throughout Latin America: Venezuelan and eastern equine encephalitis viruses (VEEV, EEEV) in both North and South America, and western equine encephalitis virus (WEEV) from Canada to Argentina. Others such as Mayaro (MAYV), UNA (UNAV), and Aura (AURA) viruses have a more restricted distribution, and chikungunya virus (CHIKV) was recently introduced into Latin America. The evolutionary patterns show clades correlated with host/reservoirs (nonhuman primates, birds, and rodents) and distinctive human disease syndromes such as fever/rash/arthralgia and encephalomyelitis. The majority of alphaviruses cause at least mild febrile disease in humans and several produce severe, life-threatening diseases, whereas others are little studied epidemiologically and their public health importance is unknown. Recent studies in Latin America of “dengue-like” illness in several locations have revealed that many alphaviruses such as VEEV, EEEV, MAYV, and CHIKV are misdiagnosed as dengue; moreover, with the recent introduction of Zika virus, diagnosis based only on signs and symptoms is even more complicated in areas where these viruses are circulating simultaneously. This chapter describes important aspects of the alphaviruses in the region including evolution, outbreaks, vector–host, and eco-epidemiological/molecular determinants of their emergence from the New World viruses and chikungunya.