A species name is written in italics with the first word beginning with a capital letter. Other words only begin with a capital if they are proper nouns (including host genus names but not virus genus names**) or alphabetical identifiers. A species name should not be abbreviated. Examples:
Some host genus names may also be considered common nouns in English and can be written in lower case where they are not the first word of the species name. Example:
A virus name should never be italicized, even when it includes the name of a host species or genus, and should be written in lower case. This ensures that it is distinguishable from a species name, which otherwise might be identical. The first letters of words in a virus name, including the first word, should only begin with a capital when these words are proper nouns (including host genus names but not virus genus names) or start a sentence. Single letters in virus names, including alphanumerical strain designations, may be capitalized. In most texts, virus names are used much more frequently than species names and may, therefore, be abbreviated. Examples:
A higher taxon name is written as a single word with a taxon-specific suffix. Examples:
order ...virales family ...viridae subfamily ...virinae genus ...virus
Like a species name, a higher taxon name is written in italics and begins with a capital letter. This differs from the convention in botany and zoology, in which taxon names above the level of genus are not italicized. Taxon names are often preceded by a taxon level identifier. Examples:
A collective name for a group of viruses belonging to a higher level taxon is neither italicized nor capitalized, even if it was derived from a proper noun. The first letter of a collective name may be capitalized if it begins a sentence.
Note that if taxa have the same stem (e.g. Flavivirus and Flaviviridae), this may lead to ambiguity because both groups of viruses could be referred to as flaviviruses. Some virologists use the terms stem + virads, stem + virids, stem + virins, and stem + virus to distinguish members of orders, families, subfamilies and genera, respectively.
Complex example sentences
*This guide does not address the rules for naming taxa, which can be found in the ICTV Code <https://talk.ictvonline.org/information/w/ictv-information/383/ictv-code>
** A proper noun is a name used for an individual person, place, or organization. A common noun denotes a class of objects or a concept. Host genus names are normally considered as proper nouns because they refer to a group of unique entities but some, for example "citrus", have become common nouns because they can also describe intergeneric hybrids. Virus genus names are not considered as proper nouns when used as part of a species or virus name because they refer to a subset of the genus and not the genus as a whole.