Chikungunya Virus as the Agent of Emergent Viral Disease

Abstract

Chikungunya virus belongs to Alphavirus genus of the Togaviridae family. It is a member of Semliki Forest virus antigenic complex that includes antigenic related Semliki Forest, Chikungunya, O’ Nyong-nyong, Ross River viruses. Chikungunya virus is the causative agent of acute febrile illness with myalgia and arthralgia in humans. Since its discovery in 1952, Chikungunya virus caused sporadic and infrequent outbreaks. Since 2004, global Chikungunya outbreaks have occurred. Now Chikungunya is viewed as a global public health issue in many countries, where Aedes mosquito vectors are widespread. Currently, four genotypes of Chikungunya virus (West African, South African, Asian and Indian Ocean) are distinguished. Appearance of different genotypes is associated with adaptive mutations in peplomers of E1 and E2 glycoproteins. It is shown, that a single mutation in E1 glycoprotein (alanin for valin substitution in 226 position) leads to increasing virus virulence (50-100 times). This mutation is instrumental for epidemic potential increase. For virus variants with this mutation, secondary substitutions enhancing viral virulence are described too. А edes aegypti mosquitoes are common vector for all genotypes of Chikungunya virus, А edes albopictus mosquitoes are vector, mainly, for South African and Asian genotypes. They play the leading role in epidemic potential increase over the last decade. The effectiveness of Chikungunya virus transmission by А edes а egypti mosquitoes is 83.3 %, by А edes albopictus mosquitoes - 96.7 %. The А edes albopictus are more widely disseminated than А edes а egypti (about 40 percent of all land territory). Demonstrated is the possibility of transcontinental spread of А edes albopictus mosquitoes by aviation and naval transport. This review highlights the most recent advances in our knowledge of the ecology, epidemiology and molecular biology of Chikungunya virus. These data play an important role in the development of preventive, treatment and vaccination strategies of Chikungunya fever.