* Problems with viral vectors – Viruses, the carrier of choice in most gene therapy studies, present a variety of potential problems to the patient: toxicity, immune and inflammatory responses, and gene control and targeting issues.

Viruses were confirmed as human pathogens in 1901, with the discovery of the yellow fever virus by Walter Reed.

: Viruses with amber mutations are characterized by their ability to infect only certain strains of bacteria, known as amber suppressors.

Viruses range in size from about 30 nm to about 450 nm, which means that most of them cannot be seen with light microscopes.

Viruses consist of a genome and sometimes a few enzymes stored in a capsule made of protein ( called a capsid ), and sometimes covered with a lipid layer ( sometimes called an ' envelope ').

Viruses that have a lipid envelope must also fuse their envelope with the target cell, or with a vesicle that transports them into the cell, before they can uncoat.

According to the rules for taxon naming established by the International Committee on Taxonomy of Viruses ( ICTV ), the name Ebola virus is always to be capitalized, but is never italicized, and may be abbreviated ( with EBOV being the official abbreviation ).

In March 1998, the Vertebrate Virus Subcommittee proposed in the International Committee on Taxonomy of Viruses ( ICTV ) to change the Filovirus genus to the Filoviridae family with two specific genera: Ebola-like viruses and Marburg-like viruses.

" Viruses of the Mind " ( 1993 ) is an article by Richard Dawkins using memetics and analogies with biological and computer viruses, and with disease and epidemiology, to analyse the propagation of ideas and behaviours.

Fred Cohen, in his 1984 paper, Experiments with Computer Viruses has credited Adleman with coining the term " virus ".

* Emergent Viruses, the adaptation of a virus to emerge as a new pathogenic strain with a new attribute in a new field not normally associated with that specific virus

Viruses have been used to deliver a normal gp91 gene to rats with a mutation in this gene, and subsequently the phagocytes in these rats were able to produce oxygen radicals.

Viruses with RNA genomes are not able to package DNA and so do not usually make this mistake.

In March, 1998, the Vertebrate Virus Subcommittee proposed in the International Committee on Taxonomy of Viruses ( ICTV ) to change the Filovirus genus to the Filoviridae family with two specific genera: Ebola-like viruses and Marburg-like viruses.

Navis presumably have advanced data to prevent tampering with their code directly: Viruses cannot harm them by corrupting their data, unlike viruses of our age, who cannot do anything but this.

The 39th Executive Committee ( EC39 ) of the International Committee on Taxonomy of Viruses ( ICTV ) met in Canada during June 2007 with new taxonomic proposals.

Viruses are extremely small and can only be observed with an electron microscope.

Viruses can be spread by direct transfer of sap by contact of a wounded plant with a healthy one.

These have in turn been subsumed under the new order Tymovirales along with the old family Tymoviridae by the International Committee on Taxonomy of Viruses based on molecular phylogenetic systematic analyses of proteins ( RNA polymerase and viral coat ).

*" Virustat, a Device for Continuous Production of Viruses ," Applied Microbiology, 14 ( 6 ): 940 – 952 ( 1966 November ) with Leslie S. Jacobson.

Therefore, the optimal mutation rate for a species is a trade-off between costs of a high mutation rate, such as deleterious mutations, and the metabolic costs of maintaining systems to reduce the mutation rate, such as DNA repair enzymes .< ref name = Sniegowski > Viruses that use RNA as their genetic material have rapid mutation rates, which can be an advantage since these viruses will evolve constantly and rapidly, and thus evade the defensive responses of e. g. the human immune system.

# Viruses arose from non-living matter, separately from yet in parallel to cells, perhaps in the form of self-replicating RNA ribozymes similar to viroids.

Therefore, the optimal mutation rate for a species is a trade-off between costs of a high mutation rate, such as deleterious mutations, and the metabolic costs of maintaining systems to reduce the mutation rate, such as DNA repair enzymes .< ref name = Sniegowski > Viruses that use RNA as their genetic material have rapid mutation rates, which can be an advantage since these viruses will evolve constantly and rapidly, and thus evade the defensive responses of e. g. the human immune system.

Viruses in the family Reoviridae have genomes consisting of segmented, double-stranded RNA ( dsRNA ).

Viruses that use RNA as their genetic material have rapid mutation rates, which can be an advantage since these viruses will evolve constantly and rapidly, and thus evade the defensive responses of e. g. the human immune system.

Pseudoviridae is classified under group VI RNA Reverse Transcribing Viruses and infect fungi and invertebrates.

* Viruses with polycistronic mRNA where the genome RNA forms the mRNA and is translated into a polyprotein product that is subsequently cleaved to form the mature proteins.

* Viruses containing nonsegmented genomes for which the first step in replication is transcription from the negative-stranded genome by the viral RNA-dependent RNA polymerase to yield monocistronic mRNAs that code for the various viral proteins.

* Viruses with segmented genomes for which replication occurs in the nucleus and for which the viral RNA-dependent RNA polymerase produces monocistronic mRNAs from each genome segment.

# Viruses arose by genome reduction from earlier, more competent cellular life forms that became parasites to host cells and subsequently lost most of their functionality ; examples of such tiny parasitic prokaryotes are Mycoplasma and Nanoarchaea.

Viruses cannot reproduce on their own, and instead propagate by subjugating a host cell to produce copies of themselves, thus producing the next generation.

Viruses directly attack the intestinal cells, taking over their metabolic machinery to make copies of themselves, which leads to cell death.

Viruses are informative in understanding the dynamics of evolutionary change due to their rapid mutation rate and fast generation time.

* Viruses, despite having only a few genes, possess mechanisms to regulate their gene expression, typically into an early and late phase, using collinear systems regulated by anti-terminators ( lambda phage ) or splicing modulators ( HIV ).

Viruses are programs that can replicate their structures or effects by infecting other files or structures on a computer.

Viruses, as parasitic agents, are well suited to introducing DNA into cells, as this is a part of their normal course of reproduction.

Viruses use the plant ribosomes to produce the 4-10 proteins encoded by their genome.

* Electron micrographs of Orthopoxvirus and Parapoxvirus Genera, including the smallpox virus, have been collected by the International Committee on Taxonomy of Viruses in their Poxviridae picture gallery.

Viruses in this family replicate their genomes via a rolling circle mechanism and encode dedicated RCR initiation proteins.

Viruses are assigned according to their similarity to known lab based strains – the ΦX174-like clade, G4-like clade and the α3-like clade.

Viruses belonging to the Caulimoviridae family are termed DNA reverse-transcribing viruses ( or pararetroviruses ) i. e. viruses that contain a reverse transcription stage in their replication cycle.