**2. Microbiology**

CHIKV is an alphavirus belonging to the *Togaviridae* family. Alphaviruses are small and spherical, with a 60-70 nm diameter capsid and a phospholipid envelope. The RNA singlestrand of positive polarity encodes four non structural proteins (nsP1-4) and three structural proteins (C,E1,E2). Viral replication is initiated from the time of attachment of viral envelope to cellular host receptors (Strauss & Strauss, 1994). Endocitosis of the virus occurs, following which, delivery of the viral nucleocapsid into cytoplasm takes place. The replication cycle is considerably fast, taking around 4hours. Alphaviruses are sensitive to disseccation and to temperatures above 58°C (Khan et al., 2002; Strauss J.H. & StraussE.M., 1994). About 30 species of arthropod-borne viruses are included in the alphavirus genus, antigenically classified into 7 complexes. These viruses are widely distributed throughout the world, with the exception of Antarctica, and 7 of them cause a syndrome similar to Chikungunya fever, arthralgia and rash: Barmah Forest and Ross river viruses (Oceania), O'nyong-nyong and Semliki Forest viruses (Africa), Mayaro (South America), Sindbis and Sindbis-like (Africa, Asia, Scandinavia and Russia) (Taubiz et al., 2007).
