MoBio Baltimore Classification of Viruses Chapter 1

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.