Seven Viruses Causing Cancer, Including HPV & Epstein-Barr Virus

Seven viruses are known to cause human cancers, and the two most famous are HPV (human papillomavirus) and Epstein-Barr virus. HPV is the most common STI and drives nearly all cervical cancer plus throat, anal, penile, vulvar and vaginal cancers. Vaccination and screening prevent most of it.

The essentials: how a virus causes cancer

Cancer-causing viruses don't turn into cancer overnight. They insert their genetic material into your cells and, over years, can switch off the brakes that normally keep cell growth in check. Most of the time your immune system clears the virus before that happens, so infection is common while virus-driven cancer is comparatively rare. HPV is the standout example, and it's the focus here because it's sexually transmitted and largely preventable.

There are dozens of HPV types, and they split into two camps that people constantly confuse. Low-risk types (6 and 11) cause genital warts. High-risk types (16, 18 and several others) cause cancer. The types that cause warts do not cause cancer CDC, About HPV. A wart is a nuisance. It's a different problem from cancer.

In most cases — about 9 out of 10 — HPV goes away on its own within two years with no health problems at all. The danger comes from high-risk infections that persist year after year, quietly damaging cells in the cervix, throat or anal canal.

HPV's cancer toll reaches well beyond the cervix. It causes virtually all cervical cancer, over 90% of anal cancers, and about 70% of throat (oropharyngeal) cancers, and oropharyngeal cancer has now overtaken cervical cancer as the most common HPV-related cancer in the US NCI, HPV and Cancer. The full list of cancers linked to high-risk HPV: cervical, vulvar, vaginal, penile, anal, and the back of the throat.

Symptoms: usually none, which is the problem

Most HPV infections are completely silent. High-risk types typically cause no symptoms at all, which is why screening exists. You can carry, transmit, and clear high-risk HPV without ever knowing you had it.

Genital warts, caused by the low-risk types, are the one visible sign, usually a small bump or a cluster of bumps in the genital area. They may be flat, raised, or cauliflower-shaped, and they're generally painless. Because warts come from low-risk types, finding one doesn't mean you're at higher cancer risk.

Cervical precancer caused by persistent high-risk HPV produces no symptoms either, and is detected by screening rather than by how you feel. By the time cervical or throat cancer causes symptoms, the disease is usually advanced. That's the argument for catching it early.

Testing: screening, not a general STD panel

How HPV is detected depends entirely on who you are and what you're checking for. There is no all-purpose 'HPV test' you can add to a standard panel, and there isn't one for everybody.

HPV tests are not recommended to screen men, adolescents, or women under age 30 CDC, Pink Book. For women, high-risk HPV is found through cervical screening, not a general STD panel. Current guidance starts cervical screening at age 25 with a primary HPV test every five years as the preferred approach, rather than a yearly Pap ACS, Cervical Screening. That shift makes sense given the biology: most HPV clears within two years, and a primary HPV test catches more real precancer with fewer office visits than an annual smear. For the full screening details, see our guide to cervical cancer and cervical dysplasia.

Two common testing mistakes worth heading off. There's no routine HPV test for men, so men can't 'get screened for HPV' the way women do through cervical screening. And HPV testing is not used to diagnose warts — the result isn't confirmatory and doesn't guide wart treatment, so doctors diagnose warts by looking at them, not by swabbing for the virus.

Anal screening sits in a grey zone. CDC's 2021 guidance found the data insufficient to recommend routine anal cytology, even for men who have sex with men or people with HIV. That position predates the 2022 ANCHOR trial, which showed that treating high-grade anal lesions reduced anal cancer in people with HIV. Some specialty groups now suggest periodic anal Pap testing for high-risk groups where high-resolution anoscopy referral exists, though it is not a blanket CDC recommendation. If you're unsure when to check after a possible exposure, here's when to test after exposure, and you can get tested for other STIs alongside cervical screening.

Treatment: you can treat warts, but not the virus

There's no medication that cures HPV itself. Your immune system clears it, or it persists. What you can treat are the things HPV causes — warts and, separately, cancer precursors.

For genital warts, you have two routes. At home, prescription options include imiquimod 3.75% or 5% cream, podofilox 0.5% solution or gel, and sinecatechins 15% ointment, though sinecatechins aren't recommended for immunocompromised or HIV-positive patients CDC, Anogenital Warts. In the clinic, a provider can use cryotherapy (freezing with liquid nitrogen or a cryoprobe), trichloroacetic or bichloroacetic acid (TCA/BCA 80%–90% solution), or surgical removal by excision, curettage, laser, or electrosurgery.

In practice, a clinic freezes them or you apply a cream at home over several weeks, and none of the options is clearly better than the others. Treating warts doesn't remove the virus, so warts can come back after they clear. Cancer precursors — abnormal cells found on cervical screening — are managed on a completely separate track, not with wart medicine; those are handled through colposcopy and procedures coordinated by your screening clinician.

Prevention: the vaccine is cancer prevention

Three tools cut HPV cancer risk: vaccination, cervical screening, and condoms (partial protection only, since HPV can infect skin a condom doesn't cover). The vaccine is the most powerful of the three because it stops infection before it starts.

The HPV vaccine is cancer prevention with hard numbers. Given at the recommended ages, it can prevent more than 90% of HPV-caused cancers, and Gardasil 9 is about 98% effective against the precancers caused by HPV 16 and 18 ACS, HPV Vaccination. The vaccine used in the US today is Gardasil 9, which protects against nine types — 6, 11, 16, 18, 31, 33, 45, 52 and 58.

Why those nine types matter: types 16 and 18 cause about 66% of cervical cancers; the five additional high-risk types in Gardasil 9 (31, 33, 45, 52, 58) cause about another 15%; and types 6 and 11 cause more than 90% of genital warts. The older shots covered fewer types — quadrivalent Gardasil covered 6, 11, 16 and 18, and bivalent Cervarix covered only 16 and 18 — but since 2016 only the 9-valent version has been distributed in the US, so it protects against more cancer-causing types than the earlier vaccines.

The vaccine is prevention, not treatment. Gardasil 9 protects against future infection but won't clear an infection or warts you already have. And vaccinated people still need cervical screening, because no vaccine covers every cancer-causing type. Adults outside the original childhood window can often still benefit — see the hpv vaccine for adults and the dedicated guide to the hpv vaccine for adults for who qualifies.

When to see a clinician

• You notice a new bump or cluster of bumps in the genital, anal, or oral area — a clinician can diagnose warts by sight and discuss treatment.
• You're due for cervical screening — if you're a woman age 25 or older, ask about a primary HPV test rather than defaulting to a yearly Pap.
• You've never had the HPV vaccine and want to know if catch-up vaccination still makes sense for you.
• You have HIV or are immunocompromised — your provider may discuss closer monitoring and whether anal screening is appropriate where high-resolution anoscopy is available.
• You have a cervical screening result flagged as abnormal — follow up promptly, since precancer is silent until it's advanced and treatable when caught early.