Notice to Readers: Update of Recommended Nomenclature for the Genetic Characteristics of Wild-Type Rubella Viruses

The recommended nomenclature for wild-type rubella viruses is being updated by the World Health Organization on June 15, 2007 (1). Wild-type rubella virus nomenclature was first published in 2005 to facilitate 1) communication among persons involved in rubella control by establishing a standard naming convention for rubella viruses and 2) virologic surveillance by defining standard methods for the genetic characterization of these viruses. Genetic characterizations of rubella viruses have yielded data indicating that rubella is no longer endemic in the United States and confirming epidemiologic information on the source of imported cases (2,3). Results from genetic characterizations of rubella viruses are periodically summarized in updates on the global distribution of rubella virus genotypes (4). Genetic characterization of rubella viruses is conducted by the World Health Organization's measles and rubella laboratory network, a network of approximately 700 laboratories worldwide, including global specialized laboratories at the Health Protection Agency in the United Kingdom, National Institute of Infectious Diseases in Japan, and CDC in the United States (5).

The 2005 report on the recommended nomenclature for wild-type rubella viruses described seven recognized genotypes (1B, 1C, 1D, 1E, 1F, 2A, and 2B) and three provisional genotypes (1a, 1g, and 2c) (6). Genotype numbers refer to large, distantly related groups of viruses designated as clade 1 and clade 2. The letters represent genotypic groups within the clades.

Virologic surveillance in rubella-control and regional rubella-elimination programs since 2004 has resulted in approximately 100 new nucleotide sequences of wild-type rubella viruses available for analysis. These new sequences have enabled the further classification of viruses in provisional genotype 1g into one new recognized genotype (1G) and two new provisional genotypes (1h and 1i) (1). New sequence data for viruses in provisional genotype 2c enabled this genotype to be changed to a recognized genotype, 2C. In addition, identification of a group of viruses in Japan enabled the definition of another new provisional genotype (1j). The 1j provisional genotype also contains viruses originally classified as 1D, not all of which were from Japan (1). In summary, this update of the nomenclature describes 13 genotypes of wild-type rubella viruses: recognized genotypes 1B, 1C, 1D, 1E, 1F, 1G, 2A, 2B, and 2C, and provisional genotypes 1a, 1h, 1i, and 1j.

Detailed descriptions of the rationale for nomenclature changes and other related technical matters described in this update should be reviewed by those involved in the genetic characterization of rubella viruses (1). Many more wild-type rubella viruses will be characterized genetically in future years, and information from these characterizations might result in recognition of additional genotypes of wild-type rubella viruses.

References

1. World Health Organization. Update of standard nomenclature for wild-type rubella viruses, 2007. Wkly Epidemiol Rec. In press 2007.
2. Icenogle JP, Frey TK, Abernathy E, Reef SE, Schnurr D, Stewart JA. Genetic analysis of rubella viruses found in the United States between 1966 and 2004: evidence that indigenous rubella viruses have been eliminated. Clin Infect Dis 2006;43(Suppl 3):S133--40.
3. CDC. Imported case of congenital rubella syndrome---New Hampshire, 2005. MMWR 2005;54:1160--1.
4. World Health Organization. Global distribution of measles and rubella genotypes---update. Wkly Epidemiol Rec 2006;81:474--9.
5. CDC. Global measles and rubella laboratory network, January 2004--June 2005. MMWR 2005;54:1100--4.
6. World Health Organization. Standardization of the nomenclature for genetic characteristics of wild-type rubella viruses. Wkly Epidemiol Rec 2005;80:126--32.

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Date last reviewed: 6/14/2007