What Are HPV 16 and 18?

Human papillomavirus (HPV) includes many strains of a widespread virus that infects nearly everyone at some point. Each strain has a number, and HPV 16 and 18 are among the most aggressive types, and they significantly increase the risk of cervical, vaginal, and vulvar cancer in women and penile cancer in men. These strains also have links to anal and throat cancers.

But even though it’s very common, many people with HPV misunderstand it. The way it transmits between people — often through the genitals — may be the reason behind this.

“Some patients understand that HPV is a sexually transmitted virus, but others focus more on the cancer aspect and may not realize the connection,” says Jessica Wells, PhD, RN, associate professor at Emory University’s Nell Hodgson Woodruff School of Nursing. “I often find myself explaining that HPV is actually very common, and in most cases, the body clears it on its own — nothing ever comes of it.”

“My goal is always to empower patients: Come back for your appointments and follow through with the recommendations, because cervical cancer caused by HPV is almost entirely preventable,” she says. “I think people tend to gloss over the fact that it’s an STD, and their focus naturally goes to the cancer risk. But, with the right education and care, we can manage both the virus and the potential complications that come with it."

HPV 16 alone causes around 62.4 percent of cervical cancers, with HPV 18 having the second strongest link, responsible for 15.3 percent of them. Five other types cause more than 2 percent of cervical cancers each, accounting for around 20 percent of cervical cancers combined.

Does HPV 16 or HPV 18 Cause Genital Warts?

High-risk HPV strains like HPV 16 and HPV 18 don’t show any symptoms on the cervix or elsewhere. For that reason, checkups are crucial to identify whether you have cervical HPV and to find and treat any precancerous cell changes, known as dysplasia.

If a woman has a history of normal Pap tests and doesn’t have certain risk factors (such as a compromised immune system), the ACOG says that she should have one of the following tests between 30 and 65 years of age:

• A Pap test every three years
• A Pap test and an HPV test together every five years
• Just an HPV test every five years

Even though HPV is common, many women will never know that they have it, since the cervix often sheds HPV-carrying cells without treatment. This is particularly true of women under 30.

“Many times, when women acquire HPV at a young age, there is a high clearance rate, and they tend to clear it on their own without any need for procedures like colposcopies, which we used to perform a lot in the early 2000s,” says Salena Zanotti, MD, an ob-gyn at the Cleveland Clinic in Avon, Ohio. “This is because our immune systems are definitely more active the younger we are.”

What if I Test Positive for HPV 16 or 18 of the Cervix?

Based on the results of your Pap test and HPV test, your doctor can develop a plan to either treat the dysplasia, carry out further testing to rule out cancer, or recommend more frequent follow-up visits to look for additional changes.

“Paps of the cervix have been tested for a long time, and we know the changes HPV causes in the cervix,” notes Dr. Zanotti, meaning that doctors can often tell which changes to the cervix pose the most immediate danger.

If you get diagnosed with HPV, and everything else tests okay, then it is likely that the HPV will clear on its own within one or two years, if you don’t have a suppressed immune system.

If you’re concerned about an anal HPV infection, you may find that there isn’t any consistent guidance about potential testing. Zanotti says that research doesn’t recommend screening for anal HPV at the moment.

“Research hasn’t shown that anal HPV screening is more sensitive than anal cytology. Some groups recommend anal cytology for high-risk individuals, but there isn’t a consensus,” cautions Zanotti. She identifies these high-risk groups as:

• People who have human immunodeficiency virus (HIV)
• Men who have sex with men
• Women with a history of high-risk cervical, vulvar, or vaginal dysplasia or cancer
• Women with a history of cervical HPV 16 infection
• People with a history of anogenital warts

“These individuals have a higher risk of HPV causing harmful changes, which can lead to cancer,” Zanotti advises. Wells suggests that a woman with a compromised immune system, either due to HIV, lupus, an organ transplant, or another condition, may not clear the virus as efficiently as those with more effective immune systems.

Wells notes that another group has seen an increase in anal cancer.

“Right now, we’re seeing a small but noticeable increase in anal cancer cases among certain groups — specifically, older white women who are not living with HIV,” she outlines. “Traditionally, the group most significantly impacted by anal cancer has been people living with HIV. But this emerging trend in HIV-negative individuals is something we’re keeping an eye on.”

“That said, we’re still not at the point where anal cancer screening is recommended for all women as part of routine cervical cancer screening,” Wells maintains. “There are still some women who may benefit from anal cancer screening.”

• Anal cytology testing with HPV co-testing: Similar to the cervical Pap test, this involves collecting cells from the anus using a thin brush or cotton swab. These results can identify unusual cells, but they don’t provide much useful information on their own.

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• High-resolution anoscopy: This procedure uses a microscope to examine physical changes in the anus more closely once a doctor has identified abnormal cells. The health practitioner might also use cell samples for a biopsy to diagnose any cell changes and plan treatment if necessary.
• Digital anorectal examination: A doctor may insert a gloved, lubricated finger into the anus to feel for abnormal lumps or other signs of cancer.

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So in short, while anal Pap tests aren’t recommended for the general population at this time, individuals with certain risk factors might benefit from including that screening alongside their cervical Pap tests.

For years, heavy tobacco and alcohol use were the main known risk factors for developing cancer of the oropharynx — the back of the throat, including the base of the tongue and the tonsils.

Today, HPV is the primary cause of oropharyngeal cancer around the world.

The CDC recommends that all adolescents get the HPV vaccine at 11 or 12 years of age. It’s also recommended for anyone who wasn’t fully vaccinated at a younger age, up to age 26.

Zanotti notes that some parents may be hesitant to give their child the HPV vaccine because HPV is associated with sexual activity.

“I tell my patients, ‘If you vaccinated your child against measles, mumps, and rubella, they’re more likely to get HPV than they are to get rubella these days, and HPV is something that causes cancer.’ It’s pretty clear-cut. If you can do something to prevent the cancer, why wouldn’t you?” Zanotti says.

Zanotti adds that while more parents are getting their sons vaccinated against HPV, this still isn’t as common as vaccination in girls.

Still, Wells cautions that the HPV vaccine doesn’t do away with the need for safer sexual practices.

“Gardasil 9 only protects against nine HPV types, including the four higher-risk viruses,” says Wells. “There are actually hundreds of different HPV strains out there. So while the vaccine covers the most dangerous and most common ones, it’s not a shield against every single type.”

That’s why Wells encourages people to still practice safe sex.

“Even though your cancer risk is significantly lower with the vaccine, there are other HPV strains — and of course, other STDs — that you could be exposed to,” Wells says. “And for people with a uterus, it’s also vital to protect against unintended pregnancy if that’s a concern. Safe sex offers a whole range of protections — not just against HPV, but for your overall sexual health.”

• HPV types 16 and 18 are considered higher risk. They pass between people during sexual activity and can lead to cell changes in the cervix, vagina, vulva, and anus that may become cancerous. However, most people clear HPV long before it causes health problems.
• The Gardasil 9 vaccine protects against the highest-risk types of HPV, as well as some other types, and it is highly effective.
• People with HIV or other conditions that affect the immune system may have a higher risk of cancer developing and may also benefit from anal testing.
• Screening can help doctors identify and remove cells with HPV-linked changes from the cervix and other areas that are concerning. Speak to a healthcare professional about cervical screening and whether you’re a candidate for HPV testing in different areas.