(virology) A family of positive-strand ribonucleic acid (RNA)-containing viruses characterized by spherical enveloped particles with an icosahedral nucleocapsid containing linear single-stranded RNA, it contains the genera Alphavirus (arbovirus A; prototype Sindbis virus), Flavivirus (arbovirus B; prototype yellow fever), Rubivirus (rubella virus), and Pestivirus (mucosal disease virus).

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