How many strains of hpv are there

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Overview of Human Papillomavirus (HPV) Strains

Number of HPV Strains

Human papillomavirus (HPV) is a diverse group of viruses, with approximately 200 strains identified to date . Among these, around 100 strains have had their whole genomes completely sequenced. This extensive diversity is categorized into different species and strains within the genus alpha-papillomavirus.

High-Risk HPV Strains

Out of the 200 identified strains, 13 to 18 are classified as high-risk due to their strong association with anogenital cancers, particularly cervical cancer . These high-risk strains include HPV-16, HPV-18, HPV-31, HPV-33, HPV-35, HPV-39, HPV-45, HPV-51, HPV-52, HPV-56, HPV-58, HPV-59, and HPV-68 . HPV-16 and HPV-18 are the most studied and are responsible for approximately 70% of cervical cancer cases worldwide .

Phylogenetic Classification

HPV strains are phylogenetically classified into different species groups. For instance, HPV-16, HPV-31, HPV-33, HPV-35, HPV-52, HPV-58, and HPV-67 belong to the alpha-9 species group . These classifications are based on the genetic diversity and evolutionary history of the virus, which also influence their pathogenicity and geographical distribution .

Geographic and Ethnic Variations

The distribution of HPV strains can vary significantly based on geographic and ethnic factors. For example, variants of HPV-16 and HPV-18 have been found to correlate with specific geographic regions and ethnic groups, leading to unique African, European, Asian, and Native American variants . This geographic diversity is also observed in other high-risk strains like HPV-31, HPV-35, HPV-52, and HPV-58 .

Conclusion

In summary, there are approximately 200 strains of HPV, with around 100 fully sequenced. Among these, 13 to 18 strains are considered high-risk due to their association with cervical and other anogenital cancers. The phylogenetic classification and geographic distribution of these strains highlight the complexity and diversity of HPV, underscoring the importance of targeted vaccination and screening programs to manage and prevent HPV-related diseases.