Virus species polemics: 14 senior virologists oppose a proposed change to the ICTV definition of virus species.

The Executive Committee of the International Committee on Taxonomy of Viruses (ICTV) has recently decided to modify the current definition of virus species (Code of Virus Classification and Nomenclature Rule 3.21) and will soon ask the full ICTV membership (189 voting members) to ratify the proposed controversial change. In this discussion paper, 14 senior virologists, including six Life members of the ICTV, compare the present and proposed new definition and recommend that the existing definition of virus species should be retained. Since the pros and cons of the proposal posted on the ICTV website are not widely consulted, the arguments are summarized here in order to reach a wider audience.

A proposal to change existing virus species names to non-Latinized binomials.

A proposal has been posted on the ICTV website (2011.001aG.N.v1.binomial_sp_names) to replace virus species names by non-Latinized binomial names consisting of the current italicized species name with the terminal word "virus" replaced by the italicized and non-capitalized genus name to which the species belongs. If implemented, the current italicized species name Measles virus, for instance, would become Measles morbillivirus while the current virus name measles virus and its abbreviation MeV would remain unchanged. The rationale for the proposed change is presented.

The diversity of viruses infecting humans.

Most human viruses have been discovered through the diseases they cause in animals, plants, bacteria or fungi. Recent finds include human bocaviruses, which now seem to have a global distribution, and cause respiratory tract disease in infants, and several new pathogenic human coronaviruses. The SARS coronavirus, genetically distinct from all previously known coronaviruses, caused a disease which was highly transmissible and very severe, eventually leading to 8000 cases worldwide with over 800 deaths. Many viruses which are transmitted to humans by invertebrates, such as insects or ticks, have the ability to infect and replicate in cells of both vertebrate and invertebrate origin. However human virology is a rapidly expanding field and recent technologies such as the polymerase chain reaction (PCR) amplification system have made it possible to look for previously unrecognized viruses which may or may not be involved in pathogenesis. For example viruses in the genus Anellovirus are found in 80% of human blood samples yet do not seem to cause any disease. This paper overviews known human vertebrate viruses, more recent discoveries, and recommends a systematic search for viruses which may already infect the human population but have so far remained undetected.

Emerging issues in virus taxonomy.

Viruses occupy a unique position in biology. Although they possess some of the properties of living systems such as having a genome, they are actually nonliving infectious entities and should not be considered microorganisms. A clear distinction should be drawn between the terms virus, virion, and virus species. Species is the most fundamental taxonomic category used in all biological classification. In 1991, the International Committee on Taxonomy of Viruses (ICTV) decided that the category of virus species should be used in virus classification together with the categories of genus and family. More than 50 ICTV study groups were given the task of demarcating the 1,550 viral species that were recognized in the 7th ICTV report, which was published in 2000. We briefly describe the changes in virus classification that were introduced in that report. We also discuss recent proposals to introduce a nonlatinized binomial nomenclature for virus species.