Baltimore classification
Baltimore classification is a system used to classify viruses by their routes of transferring genetic information from the genome to messenger RNA (mRNA). Seven Baltimore groups, or classes, exist and are designated by the Roman numerals I to VII. Groups are defined by whether the viral genome is composed of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA); whether the genome is single- or double-stranded; and whether the virus makes DNA from RNA (reverse transcription (RT)).