Definition and epidemiology
Human papillomavirus (HPV) is a non-enveloped, double-stranded DNA virus of the Papillomaviridae family. It infects squamous epithelium of the skin and mucous membranes, including the cervix, vagina, vulva, penis, anus, and oropharynx.
HPV is the most common sexually transmitted infection worldwide. Most sexually active individuals acquire at least one genital HPV type during their lifetime, and the majority of infections are transient, cleared by the immune system within 1-2 years.
- Peak prevalence occurs in the late teens to twenties, shortly after onset of sexual activity.
- Over 150 genotypes exist, divided into low-risk (non-oncogenic) and high-risk (oncogenic) types based on their association with malignancy.
- High-risk types 16 and 18 are responsible for the large majority of HPV-associated cancers; types 6 and 11 cause most anogenital warts.
- HPV-related cervical cancer remains a leading cause of cancer death in women in regions without organized screening or vaccination programs.
- HPV 16 and 18 cause roughly 70% of cervical cancers worldwide.
- HPV 6 and 11 cause roughly 90% of genital warts.
- E6 inactivates p53; E7 inactivates Rb — the key oncogenic mechanism.
- Koilocytes (perinuclear halo) are the classic cytologic clue to HPV infection.
- Most HPV infections, even high-risk types, clear spontaneously within 1-2 years.
- Condylomata lata (syphilis) are flat and smooth; condyloma acuminata (HPV) are papillary/cauliflower-like.
- HPV vaccination is most effective when given before sexual debut.
- HPV is now a major and rising cause of oropharyngeal squamous cell carcinoma.
Etiology and risk factors
HPV is transmitted primarily through direct skin-to-skin or mucosal contact during sexual activity, including vaginal, anal, and oral sex. Fomite transmission is rare but has been described for cutaneous warts. Vertical transmission from mother to infant can cause laryngeal papillomatosis.
Risk factors
- Early age at first intercourse
- Multiple sexual partners or a partner with multiple partners
- Lack of barrier contraception use
- Immunosuppression (HIV infection, transplant recipients, chronic corticosteroid use)
- Smoking, which increases risk of persistence and progression to cervical neoplasia
- Lack of HPV vaccination
- Co-infection with other sexually transmitted infections
Pathophysiology
HPV infects basal keratinocytes through microabrasions in the epithelium. Viral replication is tightly linked to the keratinocyte differentiation cycle, with viral assembly and shedding occurring in the superficial epithelial layers.
The oncogenic potential of high-risk types centers on two viral oncoproteins:
- E6 binds and promotes degradation of p53, impairing apoptosis and DNA repair.
- E7 binds and inactivates retinoblastoma protein (Rb), releasing E2F and driving uncontrolled cell cycle progression.
In most infections, the host immune response clears the virus before integration occurs. Persistent infection, especially with HPV 16/18, allows viral DNA integration into the host genome, dysregulated E6/E7 expression, and progression through cervical intraepithelial neoplasia (CIN I to III) toward invasive carcinoma over years to decades. Low-risk types (6, 11) do not integrate and instead cause benign hyperproliferative lesions (warts) through episomal replication.
Clinical features
Most HPV infections are asymptomatic and detected only through screening or incidental findings.
Low-risk HPV manifestations
- Condyloma acuminata (genital warts): soft, flesh-colored, cauliflower-like papules on vulva, penis, perianal area, or vagina
- Recurrent respiratory papillomatosis (laryngeal warts), particularly in children infected perinatally
High-risk HPV manifestations
- Usually clinically silent until premalignant or malignant disease develops
- Abnormal cervical cytology detected on routine Pap testing
- Postcoital bleeding, intermenstrual bleeding, or abnormal discharge with invasive cervical cancer
- Anal, vulvar, penile, or oropharyngeal lesions/masses in advanced HPV-associated cancers
- Oropharyngeal cancer (often tonsillar or base of tongue) presenting as a neck mass or sore throat in adults, increasingly linked to HPV 16
Diagnosis
Diagnosis depends on the clinical context (screening vs symptomatic lesion).
Cervical screening
- Pap smear (cytology): looks for koilocytes (nuclear enlargement, hyperchromasia, perinuclear halo) and dysplastic changes
- HPV DNA testing: detects high-risk genotypes; used alone or co-testing with cytology in women starting around age 25-30, per US guidelines
- Abnormal results are triaged with colposcopy and biopsy to assess for CIN
Genital warts
- Usually a clinical diagnosis based on appearance
- Biopsy reserved for atypical, pigmented, ulcerated, or treatment-resistant lesions, or in immunosuppressed patients
Other
- Anal Pap smears/HPV testing considered in high-risk groups (HIV-positive men who have sex with men)
- HPV genotyping (16/18) can further stratify risk in equivocal cytology
| Test | Purpose |
|---|---|
| Pap cytology | Detects dysplastic cervical cells |
| HPV DNA/mRNA test | Detects high-risk genotypes |
| Colposcopy + biopsy | Confirms and grades CIN |
| Clinical exam | Diagnoses genital warts |
Differential diagnosis
- Molluscum contagiosum: dome-shaped papules with central umbilication, caused by a poxvirus, not HPV
- Condylomata lata: flat, moist, highly infectious lesions of secondary syphilis, distinguished by darkfield microscopy/serology
- Seborrheic keratosis or skin tags: benign non-infectious lesions that can mimic small warts
- Molluscum vs. squamous cell carcinoma: ulcerated or fixed genital lesions in older or immunosuppressed patients warrant biopsy to exclude malignancy
- Vulvar/vaginal cysts: non-warty, smooth, fluctuant masses
- Lichen planus or lichen sclerosus: can cause genital lesions but with different morphology and distribution
Management
There is no antiviral cure for HPV itself; management targets lesions and prevents progression to cancer. Most low-risk infections and warts resolve spontaneously, but treatment reduces symptoms and transmission risk.
Genital warts
- Patient-applied: topical imiquimod, podophyllotoxin (podofilox), or sinecatechins
- Provider-administered: cryotherapy, trichloroacetic acid, surgical excision, or laser ablation
- Choice depends on lesion number, size, location, and patient preference; recurrence is common regardless of modality
Cervical dysplasia (CIN)
- CIN I: often observed, as most regress spontaneously
- CIN II-III: excisional or ablative treatment (loop electrosurgical excision procedure (LEEP), cone biopsy, or cryotherapy)
- Invasive cervical cancer is managed per oncologic staging (surgery, chemoradiation) and is outside the scope of HPV management itself
Prevention
- HPV vaccination (recombinant, covers up to 9 genotypes including 16, 18, 6, 11) is the cornerstone of primary prevention, recommended for adolescents of all sexes before sexual debut, with catch-up vaccination per national guidelines (age ranges vary slightly between WHO, ACIP/US, and European recommendations)
- Routine cervical cancer screening per age-based guidelines (cytology and/or HPV co-testing)
- Condom use reduces but does not eliminate transmission risk, since HPV infects areas not covered by condoms
- Smoking cessation reduces risk of persistence and progression
Complications and prognosis
- Most HPV infections, including both low- and high-risk types, clear spontaneously within 1-2 years without sequelae
- Persistent high-risk infection can progress through CIN to invasive cervical cancer, typically over 10-20 years
- Other HPV-associated malignancies: anal, vulvar, vaginal, penile, and oropharyngeal squamous cell carcinoma
- Recurrent respiratory papillomatosis in infants/children can cause airway obstruction and requires repeated surgical debulking
- Psychosocial impact of genital warts and recurrence after treatment is common
- Prognosis for HPV-associated oropharyngeal cancer is generally better than for HPV-negative (often smoking-related) oropharyngeal cancer
- Widespread vaccination has substantially reduced rates of high-grade cervical dysplasia and genital warts in vaccinated cohorts
"6, 11 = Low-risk Lesions (warts); 16, 18 = Highly-oncogenic" — remember low numbers (6, 11) make benign condylomas, while 16 and 18 drive cancer via E6 (p53) and E7 (Rb) inactivation.
Practice questions
1. A 24-year-old woman undergoes routine cervical cytology, which shows cells with enlarged, hyperchromatic nuclei surrounded by a clear perinuclear halo. Which of the following best describes the underlying cause of this cytologic finding?
2. A 35-year-old woman is found to have persistent infection with a high-risk HPV genotype. Researchers studying her cervical biopsy find that the viral E7 protein is binding to and inactivating a host tumor suppressor protein, leading to unchecked release of a transcription factor that drives cell cycle progression. Which host protein is being inactivated?
3. A 19-year-old sexually active woman asks about the best way to reduce her risk of HPV-related cervical cancer. She has not yet received the HPV vaccine and has had two prior sexual partners. Which of the following is the most appropriate recommendation?
Frequently asked questions
What causes HPV infection?
HPV infection is caused by direct skin-to-skin or mucosal contact with one of over 150 human papillomavirus genotypes, most commonly through vaginal, anal, or oral sexual contact. Low-risk types like 6 and 11 cause genital warts, while high-risk types like 16 and 18 can cause cervical and other cancers. Vertical transmission during childbirth can also occur, though it is less common.
What are the first symptoms of HPV?
Most people with HPV have no symptoms at all, since the immune system often clears the infection before any changes occur. When symptoms do appear, the earliest sign is often small, painless, flesh-colored genital or anal warts. High-risk HPV typically causes no symptoms until it leads to abnormal Pap smear results or, much later, cervical or other cancers.
How is HPV diagnosed?
HPV is diagnosed primarily through cervical screening using a Pap smear and/or HPV DNA test, which detect high-risk genotypes or precancerous cellular changes. Genital warts are usually diagnosed by visual clinical examination without the need for additional testing. Abnormal screening results are followed by colposcopy and biopsy to confirm the diagnosis and assess severity.
Is HPV curable?
There is no medication that cures the HPV virus itself, but most infections (including high-risk types) are cleared naturally by the immune system within one to two years. Treatments target the visible warts or abnormal cervical cells caused by the virus, not the virus itself. Persistent infection, rather than the initial infection, is what carries the risk of progressing to cancer.
HPV warts vs genital herpes — what is the difference?
Genital warts (HPV) are typically painless, flesh-colored, cauliflower-like growths that persist and slowly enlarge, while genital herpes causes painful, grouped vesicles or ulcers that recur periodically and are often preceded by tingling or burning. Herpes is caused by HSV-1 or HSV-2 and diagnosed by PCR or viral culture of lesion fluid, whereas HPV warts are diagnosed clinically or by biopsy.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: B97.7
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.