IFIH1 and infection: In teleost fish, the homologue of human MDA5 has been characterized functionally only in rainbow trout, Oncorhynchus mykiss, which was responsive to the infection of RNA viruses, such as viral haemorrhagic septicaemia virus and salmon alphavirus.19 In the present study, the MDA5, and its shorter splicing variants, named as MDA5a and MDA5b, were identified in zebrafish, Danio rerio.