What are Human Papillomavirus (HPV) infections?

Human Papillomavirus (HPV) Infections

Human papillomavirus (HPV) infections are the most common sexually transmitted infections in the United States, with an estimated 6.2 million new infections occurring annually and approximately 79 million people currently infected. 1

Viral Characteristics and Types

• HPV is a family of small double-stranded DNA viruses that infect squamous epithelia, with approximately 100 HPV types identified, over 40 of which infect the genital area 1, 2
• HPV types are categorized according to their association with cancer development 1:
  • Low-risk types (e.g., HPV 6 and 11) cause benign conditions such as genital warts and recurrent respiratory papillomatosis 1
  • High-risk types (e.g., HPV 16,18,31,33,35,39,45,51,52,56,58,59,68,69,73, and 82) can cause low-grade and high-grade cervical cell abnormalities and anogenital cancers 1

Transmission

• HPV is primarily transmitted through sexual contact, including vaginal, anal, and oral sex 3
• Transmission can also occur through non-penetrative genital contact (oral-genital, manual-genital, and genital-genital), though this is less common than through sexual intercourse 1
• Microabrasions in epithelial surfaces during sexual contact provide access for the virus to reach basal keratinocytes, which are the target cells for HPV infection 3
• Risk factors for transmission include:
  • Number of sexual partners (lifetime and recent) - the most consistent predictor of infection 1
  • Partner sexual behavior 1
  • Immune status 1
  • Current tobacco use, marijuana use, and alcohol use 3
• Nonsexual transmission routes are uncommon but include vertical transmission from mother to newborn during childbirth 1, 3

Natural History and Prevalence

• Most HPV infections (70%) are transient and asymptomatic, clearing spontaneously within 1 year; approximately 90% clear within 2 years 1, 3
• The median duration of new HPV infections is approximately 8 months 1
• Persistent infection with high-risk HPV types is the most important risk factor for developing cervical cancer precursors and invasive cervical cancer 1
• HPV prevalence is highest among sexually active individuals under 25 years of age 1
• Point prevalence of oral HPV infection is approximately 7%, with a bimodal age distribution showing peaks between ages 30-34 and 55-64 years 3
• Men have 2-3 times higher rates of oral HPV infection compared to women 3

HPV-Associated Diseases

Benign Conditions

• Genital warts (condylomata acuminata):

  • Caused primarily by HPV types 6 and 11 (90% of cases) 4
  • Can occur on multiple anatomical sites including external genitalia, perineum, perianal skin, uterine cervix, vagina, urethra, and anus 4
  • Often asymptomatic but may cause pruritus, pain, tenderness, and friability 4
  • If left untreated, may resolve spontaneously, remain unchanged, or increase in size or number 4
  • Recurrence is common (approximately 30%) regardless of treatment method 4

• Recurrent respiratory papillomatosis (RRP):

  • Rare condition characterized by recurrent warts in the upper respiratory tract, particularly the larynx 1
  • Primarily caused by HPV types 6 and 11 1
  • Juvenile onset RRP is believed to result from vertical transmission during delivery 1

Malignant Conditions

• HPV is associated with several cancers 1, 5, 6:

  • Cervical cancer (nearly 100% of cases)
  • Anal cancer
  • Vaginal cancer
  • Vulvar cancer
  • Penile cancer
  • Oropharyngeal cancer
  • Some oral cavity and pharyngeal cancers

• HPV types 16 and 18 are responsible for approximately 70% of cervical cancers worldwide 1

• An estimated 34,788 new HPV-associated cancers occurred in the United States in 2009 1

• Approximately 4-4.5% of all diagnosed human malignant neoplasms are attributable to HPV 6, 2

Diagnosis

• Most HPV infections are asymptomatic and detected through screening or when visible lesions (warts) appear 7
• Genital warts are typically diagnosed clinically, though biopsy may be needed in uncertain cases 4
• Type-specific HPV nucleic acid tests are not recommended for routine diagnosis or management of visible genital warts 4
• Biopsy is indicated in specific circumstances, including uncertain diagnosis, lesions unresponsive to standard therapy, worsening during therapy, immunocompromised patients, and pigmented or ulcerated lesions 4

Prevention and Management

• HPV vaccines are available that protect against the most common high-risk HPV types 1
• The quadrivalent HPV vaccine protects against types 6,11,16, and 18, while the bivalent vaccine protects against types 16 and 18 1
• Vaccination is recommended for females aged 11-12 years, can be administered as young as age 9, with catch-up vaccination for females aged 13-26 years 1
• Consistent condom use might reduce the risk for HPV and HPV-associated diseases but cannot completely prevent transmission as the virus can infect areas not covered by condoms 1, 3
• No specific antiviral treatment exists for HPV infection itself; treatment focuses on removing visible lesions (warts) through methods such as cryotherapy, topical treatments, or surgical removal 1, 8
• Treatment of visible warts may reduce but probably does not eliminate infectivity 4
• Regular cervical cancer screening is essential for early detection of precancerous lesions 1

Important Distinctions from Other STIs

• Unlike herpes simplex virus (HSV), HPV does not establish lifelong latent infection in neural ganglia 8
• Most HPV infections clear spontaneously, while HSV remains dormant with potential for recurrent outbreaks 8
• HPV testing is not routinely recommended for asymptomatic individuals except in cervical cancer screening programs 8