Introduction
Papillomaviruses (PV) are a diverse group of viruses that belong to the Papillomaviridae family. They are small, non-enveloped viruses with a circular double-stranded DNA genome. PV are known to infect a wide range of vertebrate species, including humans.1-6 PV are highly species-specific, meaning that different types of papillomaviruses typically infect specific animal species. For instance, human papillomaviruses (HPV) infect humans, bovine papillomaviruses (BPV) infect cattle, and canine papillomaviruses (CPV) infect dogs.2,7-11
HPV are the most extensively studied and clinically significant group of PV in humans. They have more than 200 identified types, and each type is designated with a number (e.g., HPV-16, HPV-18, etc.). HPV can be categorized into low-risk types and high-risk types based on their association with different diseases.10-13 Low-risk HPV, such as HPV-6 and HPV-11, are associated with the development of benign warts, known as papillomas. These warts commonly occur on the skin and mucous membranes of the anogenital region, including the genitals and anus. They can also appear on other parts of the body, such as the hands and feet. Low-risk HPVs rarely lead to cancer.3,12-17 High-risk HPV, including HPV-16, HPV-18, HPV-31, HPV-33, HPV-45, and others, have the potential to cause various types of cancer. The most significant cancer associated with high-risk HPV is cervical cancer, which is the fourth most common cancer in women worldwide. High-risk HPV can also cause other anogenital cancers, such as anal, vaginal, vulvar, and penile cancers. Additionally, they have been linked to a subset of head and neck cancers, particularly oropharyngeal cancer.3,11,13,16,17
Transmission of HPV occurs primarily through sexual contact, including vaginal, anal, and oral sex. However, other routes of transmission, such as vertical transmission from mother to child during childbirth or non-sexual skin-to-skin contact, can also contribute to HPV infection.6,8 HPV infects the basal cells of epithelial tissues, where they establish a persistent infection. Most HPV infections are transient and resolve spontaneously within a couple of years without causing any symptoms or long-term health problems. However, persistent infections with high-risk HPV can lead to abnormal cellular changes, such as precancerous lesions, which may progress to cancer over time.1,18-22
Prevention of HPV infections primarily focuses on HPV vaccination and promoting safe sexual practices. HPV vaccines are highly effective in preventing infection with the most common high-risk HPV types and have the potential to reduce the incidence of HPV-related diseases, including cervical cancer.23-27 Safe sex practices, including condom use and limiting sexual partners, can help reduce the risk of HPV transmission.16,23-25,27-30 Regular screening, such as cervical cancer screening with Pap smears or HPV testing, is also important for the early detection of abnormal cellular changes and timely intervention.24-28
This study aimed to carry out a literature review considering several aspects involving HPV infection: Global distribution, prevalence, biology, host interactions, cancer development, prevention, therapeutics, coinfection with other viruses, coinfection with bacteria, association with head and neck squamous cell carcinomas (HNSCC), and association with anal cancer.