As an RNA virus (plural RNA viruses synonymous RNA virus, Ribovirus ) refers to viruses whose genetic material ( genome) of RNA ( Abbreviation for ribonucleic acid, " ribonucleic acid " ) is. RNA viruses is a non- taxonomic collective term that has no kinship references.
An accurate classification of RNA viruses is carried out in 3 groups ( double-stranded RNA genome), 4 ( single-stranded RNA genome of positive polarity ) and 5 ( single-stranded RNA genome of negative polarity) in the taxonomy of viruses and virus classification. Retroviruses, the RNA is transcribed during replication in virus-infected host cell by an enzyme, the reverse transcriptase into DNA. Retroviruses do not belong, according to the ICTV RNA viruses.
Among the RNA viruses include most plant viruses, many animal viruses and some bacteriophages. RNA viruses may coated or uncoated, single or double stranded RNA, positive or negative-strand oriented present segmented or unsegmentiertem genome.
RNA viruses are much more variable than DNA viruses because of the increased error rate of the RNA polymerases because their RNA polymerase mostly has no proof-reading exonuclease function. This produce RNA viruses can be more defective, non -infectious viral particles, which is called due to the loss of function as a fitness cost. However, you can adapt in the course of an immune evasion also faster to new hosts or between hosts and escape by fleeing mutation of the immune response. The excitation of the vast majority of emerging viral infectious diseases in recent decades (variations of influenza viruses, SARS, Ebola virus), but also the already thousands of years old rabies pathogens are RNA viruses.
The lower compared to DNA viruses genetic preservation or by the high genetic variability vaccines have to be frequently adapted to currently circulating strains of the virus. Thereby determining the temporal evolution of RNA viruses in terms of a molecular clock is equally difficult.
As part of the co-evolution of RNA viruses and their hosts various mechanisms for defense against RNA viruses have emerged in the host. The resistance factors of man against RNA viruses include RNA interference, some PAMP - receptors, protein kinase R. In addition, the immune response occurs. However, RNA viruses, additional mechanisms to circumvent the resistance developed.