Warts are small, rough growths on the skin caused by the human papillomavirus (HPV). There are over 100 types of HPV that can cause warts on different parts of the body. Common warts, plantar warts, flat warts, and genital warts are all caused by different strains of the HPV virus. With such a strong connection between HPV and warts, it’s natural to wonder – does everyone with warts have HPV?
Overview of HPV
HPV is short for human papillomavirus. It is an extremely common virus that infects the skin and mucous membranes. There are over 100 identified types of HPV, with 40 types that specifically infect the genital areas. Different types of HPV are associated with different health conditions:
- Low-risk HPV types – Cause minor conditions like skin warts and genital warts.
- High-risk HPV types – Can lead to serious cancers in the cervix, vulva, vagina, penis, anus, and throat.
HPV is primarily transmitted through skin-to-skin contact and sexual activity. Since it infects the basal layer of epithelial cells, surfaces like the skin, genitals, mouth, and throat are common sites of infection.
Many people contract HPV at some point in their lives – studies estimate up to 80% of sexually active individuals have been exposed. However, most never develop symptoms or health issues and the infection resolves on its own.
When HPV does cause visible changes, warts are the most common manifestation.
The link between warts and HPV
There is an extremely strong association between HPV infection and all types of warts. However, not all strains of HPV cause warts. The ones that do are referred to as the “cutaneous types” because they specifically infect the skin and mucous membranes.
Here’s a breakdown of the common wart types and their associated HPV strains:
Common warts
Also called verrucas, common warts have a rough, bumpy texture and occur anywhere on the hands and feet. They are caused by HPV types 1, 2, 4, 27, 29, and 57.
Plantar warts
These warts grow on the soles of the feet and can be flattened or raised. HPV types 1, 2, 4, 27, 28, and 58 are responsible.
Flat warts
As the name suggests, these are flat, smooth warts that can occur almost anywhere on the body. They are caused by HPV types 3, 10, 28, and 41.
Genital warts
Genital warts affect the moist tissues of the genital area. They are soft, skin-colored growths that appear singly or in clusters on the vulva, vagina, cervix, penis, scrotum, or anus. They are caused by low-risk HPV types 6 and 11.
Oral warts
Oral warts can develop on the lips, tongue, gums, and inside the mouth. HPV types 2, 6, 7, 13, and 32 cause them.
Periungual warts
These warts affect the fingers and toes, growing under and around the nails. HPV types 1, 2, 4, 27, 28, 29, and 57 are responsible.
Based on the strong correlation between HPV types and warts on different body parts, most warts are assumed to be caused by an HPV infection. However, it’s difficult to directly test the wart tissue for the presence of the virus.
Can you have warts without an active HPV infection?
While most warts are linked to an active HPV infection, there are some instances where warts can develop without an ongoing infection:
Latent HPV
HPV can remain dormant or inactive in skin cells after the initial infection resolves. Later, it can become reactivated and trigger wart formation. So while the person may not have an active infection, the wart is still caused by the latent HPV in the body.
Genetic susceptibility
Some people may be genetically prone to developing warts. They can form common warts even without an active HPV infection due to abnormal keratin production in the skin. However, this is less common than warts caused by HPV.
Skin damage
In rare cases, irritation, cuts, burns, or chronic skin damage at a site can trigger excess keratin production and wart growth even without HPV. Again, this is an uncommon reason for wart development.
Wart virus remains
Even after the HPV infection has been cleared, remnants of the virus may remain in skin cells. This viral debris can still stimulate wart formation.
So while warts may not always represent an ongoing, active HPV infection, they were likely caused by HPV exposure at some point.
How accurate are HPV tests on warts?
Since there is such a strong connection between HPV and all common wart types, testing warts for the presence of HPV might seem like an accurate way to confirm the diagnosis. However, HPV testing has limitations:
Low sensitivity
HPV can be difficult to directly detect in wart tissue due to the virus’s tendency to penetrate deep into the dermis and epidermis. The outermost layers of the wart often contain only small amounts of HPV material. This makes biopsy and PCR testing for HPV DNA inconsistent.
Risk of false negatives
Even if a biopsy specimen contains some HPV genetic material, there may not be enough to trigger a positive test result. This limits the sensitivity of HPV testing on warts.
Many HPV strains
Since there are over 100 strains of HPV and many different types can cause warts, testing would need to cover a broad range of strains. Most PCR assays only screen for a handful of common strains.
Viral inactivity
As mentioned earlier, the HPV virus can become dormant or inactive within skin cells after initial infection. In such cases, the virus may be undetectable on testing even though it is still inducing wart formation.
Due to these factors, HPV testing of warts is not considered a reliable way to confirm the diagnosis. Warts are typically diagnosed just on their clinical appearance.
What percentage of warts are caused by HPV?
Based on current scientific evidence, it is estimated that HPV is responsible for:
- Over 99% of cervical/genital warts
- 95-99% of common cutaneous warts
- Over 90% of plantar warts
- Around 80% of oral warts
So while HPV may not be detectable in all wart biopsies, the vast majority are associated with HPV infection. Some studies using advanced PCR techniques have detected HPV DNA in up to 100% of common cutaneous warts sampled.
For practical purposes, dermatologists diagnose and treat warts clinically under the assumption that HPV is the cause.
Risk factors for developing warts
While HPV exposure is required for wart development, not everyone with the virus gets warts. There are some factors that can increase susceptibility:
- Impaired immunity – People with weakened immune systems are less able to suppress active HPV infections.
- Prior skin damage – Cuts, burns, eczema, etc. can allow HPV easier entry into the skin.
- Youth – Children and teens tend to get more warts as their immune system maturity develops.
- Moist surfaces – Areas that remain damp like hands, feet, and genitals promote HPV infection and wart growth.
- Occlusion – Tight shoes, gloves, and clothing that rub and trap HPV on the skin increase wart risk.
- Personal care items – Using razors, towels, etc. of infected individuals can transmit HPV.
Avoiding skin damage, reducing occlusion, practicing good hygiene, and strengthening immunity can help lower risk of developing warts.
Can warts recur after treatment?
Unfortunately yes, warts are notorious for recurring after being removed by freezing, lasers, chemicals, or excision. Recurrence happens because:
- HPV particles remain – Complete eradication of HPV from the skin is difficult to achieve.
- Incomplete removal – Wart roots deep in the skin may persist.
- Latent virus reactivated – Dormant HPV in skin cells becomes active again.
To minimize recurrence risk,allow time between treatments for the skin to fully heal. This reduces the chance of spreading residual HPV to new areas. Consistent follow up is also important to catch and re-treat any early signs of recurrence.
Ultimately, the immune system plays a key role in suppressing HPV activity long-term. So staying healthy and avoiding immune suppression can help prevent wart recurrence.
Will warts resolve without treatment?
Left untreated, the outlook for warts depends on the person’s immune function and wart location:
Individuals with intact immunity
In healthy people, about 65-79% of cutaneous warts may spontaneously resolve within 1-2 years. The body’s defenses are eventually able to control HPV and eliminate wart growths.
Immunocompromised individuals
Those with weakened immune systems may be less likely to have warts disappear on their own. The HPV infection is harder to contain without adequate immune function.
Plantar and genital warts
Due to constant pressure and moisture, warts on the feet and genitals are less likely to resolve without treatment. Only about 30% disappear on their own within 2 years.
So while warts can go away without treatment, they often persist longer, recur, and spread. Leaving them untreated allows ongoing HPV transmission as well. For these reasons, having warts treated is recommended.
Prevention
Since virtually all warts are caused by HPV exposure, preventing HPV infection is key to reducing wart risk:
- HPV vaccination – Getting children and teens immunized before sexual activity begins offers excellent protection against strains most linked to warts and cancers.
- Safe sex – Using condoms/barriers consistently and properly limits genital HPV transmission.
- Limit partners – Having few sexual partners reduces HPV exposure.
- Don’t share items – Avoid using razors, towels, etc. of infected individuals.
- Protect skin – Keep hands, feet protected to avoid HPV entering through cuts, bites, hangnails.
- Quit smoking – Smoking weakens immunity and increases risk of HPV-related issues.
- Immune health – Get adequate rest, nutrition and exercise to optimize immune defenses against HPV.
While not completely preventable, these key measures can significantly reduce the risk of developing troublesome, recurrent warts.
Conclusion
In summary:
- Many strains of human papillomavirus are known to cause different types of warts on the skin and mucous membranes.
- Nearly all common warts, plantar warts, flat warts, genital warts, and oral warts are associated with an active or previous HPV infection.
- Direct testing of warts for HPV DNA has limitations with sensitivity and false negatives.
- It is estimated HPV underlies development of 80-99% of all clinical warts, depending on the location.
- Boosting immunity, avoiding skin damage, practicing safe sex, and getting vaccinated are key prevention measures against warts.
- While warts may not always represent an active, contagious HPV infection, their strong link to HPV exposure means they should be treated and prevented as much as possible.
So while not every single wart is directly caused by an active HPV infection, the vast majority are induced by previous exposure to HPV strains that target the skin and mucous membranes. By managing HPV transmission and immunity, most troubling warts can be avoided.