Viral Genome Types

Viruses can have:

• DNA genomes (either double-stranded or single-stranded DNA)
• RNA genomes (either double-stranded or single-stranded RNA)

Distribution

• In terms of known viral species, RNA viruses make up a very large proportion of described viruses, especially those infecting animals and plants.
• However, when you include all viruses (including bacteriophages that infect bacteria), DNA viruses may actually outnumber RNA viruses overall, particularly in the environment.

Key Points:

• Among viruses that infect humans: Many high-profile viruses are RNA viruses (e.g., influenza, HIV, SARS-CoV-2, hepatitis C, Ebola).
• In the total viral world: DNA viruses, especially bacteriophages, are extremely abundant.
• In diversity: RNA viruses are very diverse because of their fast mutation rates and adaptability.

Estimates (as of 2024 knowledge):

• It's not accurate to say “most” viruses are RNA-based globally; but among human and plant pathogens, RNA viruses are highly significant.
• Among all viruses by biomass and abundance (e.g., ocean phages), DNA viruses dominate.

In summary:

A large proportion, but not the majority, of all viruses are RNA-based. It depends on the context and which hosts you consider.

In viruses affecting humans, you'll see a disproportionate number of RNA viruses. For viruses generally, most environmental viruses (especially bacteriophages) have DNA genomes.