Question: How can the RNa viral genome spread to other cells?
About the article "RNA", section "RNA genomes".

Candidate passages:
 genomes.
Like DNA, RNA can carry genetic information.
RNA viruses have genomes composed of RNA that encodes a number of proteins.
The viral genome is replicated by some of those proteins, while other proteins protect the genome as the virus particle moves to a new host cell.
Viroids are another group of pathogens, but they consist only of RNA, do not encode any protein and are replicated by a host plant cell's polymerase.
Double-stranded RNA (dsRNA) is RNA with two complementary strands, similar to the DNA found in all cells.
dsRNA forms the genetic material of some viruses (double-stranded RNA viruses).
Double-stranded RNA such as viral RNA or siRNA can trigger RNA interference in eukaryotes, as well as interferon response in vertebrates. 
An enormous variety of genomic structures can be seen among viral species; as a group, they contain more structural genomic diversity than plants, animals, archaea, or bacteria.
There are millions of different types of viruses, although only about 5,000 of them have been described in detail.
A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus, respectively.
The vast majority of viruses have RNA genomes.
Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes.
Viral genomes are circular, as in the polyomaviruses, or linear, as in the adenoviruses.
The type of nucleic acid is irrelevant to the shape of the genome.
Among RNA viruses and certain DNA viruses, the genome is often divided up into separate parts, in which case it is called "segmented".
For RNA viruses, each segment often codes for only one protein and they are usually found together in one capsid.
However, all segments are not required to be in the same virion for the virus to be infectious, as demonstrated by brome mosaic virus and several other plant viruses.
A viral genome, irrespective of nucleic acid type, is almost always either single-stranded or double-stranded.
Single-stranded genomes consist of an unpaired nucleic acid, analogous to one-half of a ladder split down the middle.
Double-stranded genomes consist of two complementary paired nucleic acids, analogous to a ladder.
The virus particles of some virus families, such as those belonging to the "Hepadnaviridae", contain a genome that is partially double-stranded and partially single-stranded.
For most viruses with RNA genomes and some with single-stranded DNA genomes, the single strands are said to be either positive-sense (called the plus-strand) or negative-sense (called the minus-strand), depending on whether or not they are complementary to the viral messenger RNA (mRNA).
Positive-sense viral RNA is in the same sense as viral mRNA and thus at least a part of it can be immediately translated by the host cell.
Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA-dependent RNA polymerase before translation.
DNA nomenclature for viruses with single-sense genomic ssDNA is similar to RNA nomenclature, in that the "coding strand" for the viral mRNA is complementary to it (−), and the "non-coding strand" is a copy of it (+).
However, several types of ssDNA and ssRNA viruses have genomes that are ambisense in that transcription can occur off both strands in a double-stranded replicative intermediate.
Examples include geminiviruses, which are ssDNA plant viruses and arenaviruses, which are ssRNA viruses of animals.
Genome size varies greatly between species.
The smallest viral genomes – the ssDNA circoviruses, family "Circoviridae" – code for only two proteins and have a genome size of only two kilobases; the largest–the pandoraviruses–have genome sizes of around two megabases which code for about 2500 proteins.
In general, RNA viruses have smaller genome sizes than DNA viruses because of a higher error-rate when replicating, and have a maximum upper size limit.
Beyond this limit, errors in the genome when replicating render the virus useless or uncompetitive.
To compensate for this, RNA viruses often have segmented genomes – the genome is split into smaller molecules – thus reducing the chance that an error in a single-component genome will incapacitate the entire genome.
In contrast, DNA viruses generally have larger genomes because of the high fidelity of their replication enzymes.
Single-strand DNA viruses are an exception to this rule, however, as mutation rates for these genomes can approach the extreme of the ssRNA virus case.
Viruses undergo genetic change by several mechanisms.
These include a process called antigenic drift where individual bases in the DNA or RNA mutate to other bases.
Most of these point mutations are "silent" – they do not change the protein that the gene encodes – but others can confer evolutionary advantages such as resistance to antiviral drugs.
Antigenic shift occurs when there is a major change in the genome of the virus.
This can be a result of recombination or reassortment.
When this happens with influenza viruses, pandemics might result.
RNA viruses often exist as quasispecies or swarms of viruses of the same species but with slightly different genome nucleoside sequences.
Such quasispecies are a prime target for natural selection.
Segmented genomes confer evolutionary advantages; different strains of a virus with a segmented genome can shuffle and combine genes and produce progeny viruses or (offspring) that have unique characteristics.
This is called reassortment or "viral sex".
Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule.
This can occur when viruses infect cells simultaneously and studies of viral evolution have shown that recombination has been rampant in the species studied.
Recombination is common to both RNA and DNA viruses. 
The genomes of viruses from this family contain monopartite, double-stranded DNA in either an open circular or linear structure.
The size of the genome is usually between 6000-8000 base pairs.
Depending on the virus, DNA can contain either one open reading frame (ORF) as observed in Petuviruses, or up to eight ORFs such as in the Soymoviruses.
Proteins found to be encoded in this virus family genome include reverse transcriptase, proteases, nucleocapsids and transactivators - there are other proteins essential for replication that have yet to be assigned a specific function.
Replication takes place in both the cytoplasm and nucleus of host cells.
Firstly, the viral genome enters the cytoplasm.
The viral DNA forms supercoiled mini-chromosome structures upon entering the host nucleus.
The viral DNA is transcribed into polyadenylated RNA which is terminally redundant (due to transcription occurring twice for some parts of the DNA).
Newly transcribed RNA enters the cytoplasm once more where it has two roles.
It can either be used as a template for viral protein synthesis, or it can undergo reverse transcription by viral encoded reverse transcriptase to make dsDNA.
This DNA can then reenter the nucleus for amplification.
As replication requires the use of RNA intermediate, viruses from the Caulimoviridae family are not true dsDNA viruses - instead they are termed DNA reverse-transcribing viruses.
As this property is also found in retroviruses, these families have been compared.
However, there are several important differences between retroviruses and viruses from the Caulimoviridae family.
Unlike retroviruses, they do not require the integration of viral genome into the host's in order to replicate and for this reason their genome does not encode the enzymatic protein integrase.
Although they do not regularly integrate into the host genome, sequences from certain Caulimoviridae, such as Petunia vein clearing virus and Banana streak virus have been found in host genomes.
These are termed Endogenous Pararetroviruses, or EPRVs. 
The viral particle binds to cell surface receptors.
This causes a conformational change in the viral capsid proteins, and myristic acid are released.
These acids form a pore in the cell membrane through which RNA is injected [http://pathmicro.med.sc.edu/virol/polio.htm].
Once inside the cell, the RNA un-coats and the (+) strand RNA genome is replicated through a double-stranded RNA intermediate that is formed using viral RDRP (RNA-Dependent RNA polymerase).
Translation by host cell ribosomes is not initiated by a 5' G cap as usual, but rather is initiated by an IRES (Internal Ribosome Entry Site).
The viral lifecycle is very rapid with the whole process of replication being completed on average within 8 hours.
However as little as 30 minutes after initial infection, cell protein synthesis declines to almost zero output – essentially the macromolecular synthesis of cell proteins is “shut off”.
Over the next 1–2 hours there is a loss of margination of chromatin and homogeneity in the nucleus, before the viral proteins start to be synthesized and a vacuole appears in the cytoplasm close to the nucleus that gradually starts to spread as the time after infection reaches around 3 hours.
After this time the cell plasma membrane becomes permeable, at 4–6 hours the virus particles assemble, and can sometimes be seen in the cytoplasm.
At around 8 hours the cell is effectively dead and lyses to release the viral particles.
Experimental data from single step growth-curve-like experiments have allowed scientists to look at the replication of the picornaviruses in great detail.
The whole of replication occurs within the host cell cytoplasm and infection can even happen in cells that do not contain a nucleus (known as enucleated cells) and those treated with actinomycin D (this antibiotic would inhibit viral replication if this occurred in the nucleus.)