Human papillomavirus, commonly known as HPV, is one of the most widespread viral infections in the world, affecting millions of people every year. While many infections clear up on their own without causing any harm, some strains can lead to genital warts or even cancer. Understanding this common virus can help people protect themselves and know what steps to take if they are diagnosed.

How Common Is HPV?

Human papillomavirus is extraordinarily common. In fact, it is considered the most common viral sexually transmitted infection (which means an infection passed from one person to another through sexual contact) in the United States and around the world. Roughly 14 million people in the United States get infected with HPV each year, according to available statistics.^[1] More than 42 million Americans are currently infected with types of HPV that can cause disease, and about 13 million Americans, including teenagers, become infected each year.^[3]

The infection is so widespread that nearly everyone who is sexually active and not vaccinated will get HPV at some point in their lives.^[1] Most people who have it don’t even realize they are infected because the virus often causes no symptoms at all. HPV affects both men and women equally, and it can be transmitted the very first time someone has sexual contact. Age plays a role in how the body responds to the virus. For people under 30, most HPV infections clear up on their own without treatment. However, the virus can persist longer in older adults, which is why regular screening becomes more important as people age.^[1]

HPV is not limited to one country or region. It is a global health concern affecting people of all backgrounds and lifestyles. The high number of infections worldwide makes HPV a significant public health issue, particularly because some types of the virus can lead to serious health problems, including various forms of cancer.

What Causes HPV Infection?

HPV is a non-enveloped, double-stranded, circular DNA virus (a type of virus with specific genetic material) that belongs to the Papillomaviridae family.^[4] There are more than 100 different types of this virus, and each type affects the body in different ways. Over 200 types of HPV have been described in scientific literature.^[5] Some types cause warts on the hands and feet, while others affect the genital area, mouth, or throat.

The virus enters the body through tiny breaks or disruptions in the skin or mucous membranes. Once inside, it infects the basal stem cells, which are the deepest layer of skin cells. The virus contains genetic information that allows it to reproduce inside these cells. Its genetic material includes seven early genes and two late genes that are necessary for the virus to spread.^[4] The viral DNA can remain separate from the host’s genetic material for a period of time, but eventually, it may integrate into the person’s own DNA. HPV tends to integrate at fragile sites in human DNA where the genetic strand is more prone to breaking.^[4]

About 30 to 40 HPV strains specifically affect the genital area, including the vulva, vagina, cervix, penis, scrotum, rectum, and anus.^[1][5] These types are usually spread through sexual contact. Many types of HPV affect the mouth, throat, or genital area, and they are easy to catch because they spread through skin-to-skin contact.^[11]

How HPV Spreads From Person to Person

HPV spreads primarily through direct skin-to-skin contact during intimate activity. The virus lives in the surface layers of the skin, so it doesn’t need to be transmitted through bodily fluids like blood or semen.^[7] A person can get HPV through vaginal, anal, or oral sex with someone who has the virus. The infection can also spread through close skin-to-skin touching during sexual activity, even without penetration.^[3][16]

One of the most concerning aspects of HPV is that people can pass the infection to others even when they have no visible signs or symptoms. This means someone could be infected for months or even years without knowing it, and during that time, they could unknowingly transmit the virus to sexual partners. Because of this silent transmission, it’s possible to contract HPV the first time someone has sex, and symptoms might not appear until weeks, months, or even years later.^[1][7]

The virus can also be transmitted by sharing sex toys with an infected person.^[11] There is limited evidence that HPV can spread indirectly through contaminated objects, though some studies suggest this might be theoretically possible.^[5] In rare cases, a mother can pass HPV to her baby during pregnancy or childbirth, which can lead to a condition affecting the baby’s throat or vocal cords.^[5][16]

Who Is at Higher Risk for HPV?

Because HPV is so common, anyone who is sexually active can get it. However, certain factors increase a person’s risk of contracting the virus or having it persist and cause health problems. Early age at first sexual intercourse is one significant risk factor. People who begin having sex at a younger age have a longer period during which they can be exposed to the virus.^[4][5]

Having multiple sexual partners increases exposure to HPV. The more partners someone has, the greater the chance they will encounter someone infected with the virus. However, it’s important to note that people can get HPV even if they have had sex with only one person in their entire life. This is because their partner may have been infected before the relationship began.^[16]

Smoking is a major risk factor for persistent HPV infection and progression to cancer. Tobacco use weakens the immune system and makes it harder for the body to fight off the virus. Similarly, people with weakened immune systems—whether from HIV infection, organ transplant medications, or other conditions—are at higher risk for persistent HPV infection and related health problems.^[4][5]

Long-term use of oral contraceptives (birth control pills) for more than five years has been associated with increased risk of cervical cancer in women with HPV.^[4] Other risk factors include chewing betel nut (a practice common in some parts of Asia) and exposure to ultraviolet light or radiation, particularly for certain types of HPV that affect the skin.^[4]

What Symptoms Does HPV Cause?

The majority of people infected with HPV never experience any symptoms at all. In fact, most never know they have the virus. In most cases, the body’s immune system defeats the infection before it can cause any problems. About 9 out of 10 HPV infections go away on their own within two years without causing any health issues.^[2][3][16]

When symptoms do occur, they vary depending on which type of HPV is involved. The most common visible sign of low-risk HPV infection is the development of warts. Genital warts (abnormal growths in the genital area) appear as small bumps or groups of bumps in the genital region. They can be small or large, raised or flat, and some look like tiny cauliflower-shaped growths or small stems.^[2][16]

In women, genital warts appear most commonly on the vulva (the outer part of the female genitals), but they can also occur near the anus, on the cervix, or inside the vagina. In men, genital warts appear on the penis and scrotum or around the anus. These warts may appear weeks, months, or even years after someone has been infected with the virus.^[1][2] Genital warts rarely cause discomfort or pain, but they can be itchy and may cause emotional distress because of their appearance.^[2]

HPV can also cause warts on other parts of the body. Common warts appear as rough, raised bumps, usually on the hands and fingers. They are typically not attractive, and they can be painful or bleed easily if injured. Plantar warts (warts on the feet) are hard, grainy growths that usually appear on the heels or balls of the feet and can cause discomfort when walking. Flat warts are slightly raised lesions that can appear anywhere on the body.^[2]

High-risk types of HPV, which are the strains that can lead to cancer, often don’t cause any symptoms at all until they have progressed to a more serious stage. This is why regular screening is so important, especially for cervical cancer. Abnormal cell changes caused by high-risk HPV can be detected through screening tests before they turn into cancer.^[1]

How Can HPV Be Prevented?

Vaccination is the most effective way to prevent HPV infection and the health problems it can cause. The HPV vaccine is safe and effective, and it protects against the types of HPV that cause most cases of genital warts and cervical cancer, as well as several other cancers.^[3][11] There are different HPV vaccines available, but in the United States, the 9-valent vaccine is currently used. This vaccine protects against nine types of HPV, including the types that cause about 90% of genital warts and the types responsible for most HPV-related cancers.^[12]

Health authorities recommend routine HPV vaccination for all adolescents at age 11 or 12 years, although vaccination can start as early as age 9. The vaccine works best when given before a person is exposed to the virus through sexual activity. For people who start the vaccine series before their 15th birthday, only two doses are needed, given 6 to 12 months apart. Those who start the vaccine on or after their 15th birthday need three doses. Catch-up vaccination is recommended through age 26 years for those not vaccinated previously.^[3][12]

For adults aged 27 to 45 years who were not vaccinated earlier, the decision to get the HPV vaccine should be made through shared discussion between the person and their healthcare provider, taking into account their individual circumstances and risk factors.^[12] The vaccine has been proven safe through extensive testing and monitoring. More than 120 million doses have been distributed in the United States, and robust data demonstrate that HPV vaccines are safe.^[12]

Besides vaccination, using condoms correctly every time during sexual activity can help reduce the risk of getting HPV. However, condoms don’t cover all the skin in the genital area, so they may not fully protect against the virus.^[3][11] Being in a mutually monogamous relationship with someone who only has sex with you can also lower risk, though it doesn’t eliminate it entirely because both partners may have been exposed to HPV before the relationship began.

For women, regular cervical screening is crucial for preventing cervical cancer. Routine screening for women aged 21 to 65 years can detect abnormal cell changes before they turn into cancer. If someone develops genital warts, stopping sexual activity until the warts are no longer present can help prevent transmission, though it’s not known exactly how long a person remains able to spread HPV after warts disappear.^[16]

How the Virus Affects the Body

When HPV enters the body through breaks in the skin or mucous membranes, it targets the basal stem cells in the deepest layer of the skin. These cells are important because they continuously divide to create new skin cells. By infecting these cells, HPV ensures that as the cells divide and move toward the surface of the skin, they carry the virus with them.

The virus doesn’t immediately cause problems. In most cases, the body’s immune system recognizes the foreign invader and mounts a defense. The immune response usually succeeds in eliminating the virus within two years. During this time, the infected person may never know they have HPV because there are no symptoms and no lasting effects.

However, in some people, the virus manages to evade the immune system and persist in the body for longer periods. When this happens, the virus continues to replicate inside cells, and over time, it can cause changes in how those cells function and grow. Low-risk types of HPV, such as types 6 and 11, cause cells to grow abnormally, forming warts. These warts are benign, meaning they are not cancerous, but they can be bothersome.^[4]

High-risk types of HPV, most notably types 16 and 18, work differently. These types produce special proteins called E6 and E7 that interfere with the normal mechanisms that control cell growth and division. In healthy cells, there are proteins that act as brakes to prevent uncontrolled growth and that trigger damaged cells to die. The E6 and E7 proteins from high-risk HPV disable these brakes, allowing cells to grow and divide without the usual controls.^[4]

When high-risk HPV persists for many years—sometimes decades—these ongoing disruptions to cell growth can lead to precancerous changes (abnormal cell changes that may develop into cancer). These are called dysplasia (abnormal development of cells). For example, in the cervix, this condition is called cervical dysplasia. If left untreated, dysplasia can progress through increasingly severe stages and eventually develop into cancer. However, this process usually takes many years, which is why regular screening can catch and treat these changes before cancer develops.^[1]

It’s important to understand that HPV alone does not cause cancer. The virus requires additional factors—called cofactors—to trigger the progression to cancer. These cofactors include smoking, deficiencies in certain vitamins like folate, prolonged immunosuppression, and other environmental or genetic factors.^[4] This is why not everyone with high-risk HPV develops cancer, and why managing other risk factors is an important part of prevention.

Nearly all cervical cancer is caused by HPV infection, and two strains—HPV16 and HPV18—account for about 70% of all cases.^[5] HPV16 is responsible for almost 90% of HPV-related cancers of the mouth, throat, and tonsils.^[5] Between 60% and 90% of other cancers, including anal, penile, vulvar, and vaginal cancers, are also linked to HPV.^[5] Every year in the United States, HPV causes about 36,000 cases of cancer in both men and women.^[3]