Baltimore Classification of Viruses

The Baltimore classification is based on genetic contents and replication strategies of viruses.  The genetic material in all types of cells is double-stranded DNA, but some viruses use RNA or single-stranded DNA to carry genetic information.

According to Baltimore classification, viruses are divided into the following seven classes:

1. dsDNA viruses
2. ssDNA viruses 
3. dsRNA viruses 
4. (+)-sense ssRNA viruses 
5. (-)-sense ssRNA viruses 
6. RNA reverse transcribing viruses
7. DNA reverse transcribing viruses

where "ds" represents "double strand" and "ss" denotes "single strand".  

Table 1-E-1.  Examples of common viruses.

•  ss = single strand; ds = double strand.
•  (+) RNA is the one which can function as mRNA for the synthesis of proteins.  (-) RNA cannot function as mRNA.
•  Reovirus and influenza virus have segmented RNA genomes; the total length is shown here.