By Bara Vaida and Mary Otto
Cancer is a set of diseases characterized by abnormal cell growth triggered by a genetic defect. Researchers know that genetic defects that cause cancer can be inherited, or the defects can be caused by environmental factors, such as smoking, and exposure to radiation. Infectious agents, such as viruses, bacteria and parasites, also can increase a person’s risk of developing cancer.
Though the full reasons why some pathogens may increase cancer risks aren’t fully understood, researchers believe they either contribute to genetic changes in cells or inhibit the body’s ability to fight cancer. Globally, infectious diseases are linked to about 12 percent of cancers, according to a Lancet Global Health article last December.
The 12 percent figure is based on 2018 data, which showed that of the 18.1 million new cases of cancer that year, about 2.2 million were attributable to infection.
There are almost a dozen infectious pathogens known to be human carcinogens, according to the National Cancer Institute. They include:
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The bacteria Helicobacter pylori (gastric cancer)
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Hepatitis B and C viruses (liver cancer)
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Epstein-Barr virus (Burkitt’s lymphoma, nasopharyngeal carcinoma, Hodgkin lymphoma)
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Human immunodeficiency virus type 1 (Kaposi sarcoma, non-Hodgkin lymphoma, cervical cancer)
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Streptococcus bovis (colorectal cancer)
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Schistosoma hematobium (bladder cancer)
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The parasite Opisthorchis viverrini (liver bile duct cancer)
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Human papillomavirus (HPV)
HPV is considered the most prevalent sexually transmitted oncovirus (the term for viruses known to cause cancer) in the U.S. There are an estimated 14 million new HPV infections each year. While most of them clear up on their own, some infections persist and progress to precancerous lesions and, eventually, cancer.
Annually, about 44,000 new cases of HPV-associated cancer occur in the U.S., according to federal data. These cancers are found in the same parts of the body as the virus: the cervix, vagina, vulva, penis, anus, rectum, mouth and throat. Overall, research has identified HPV as the probable cause of about 34,800 of these cancers.
HPV has long been linked to cervical cancer — there are an estimated 12,000 new cases a year and 4,000 deaths. There are even more HPV-associated cancers of the mouth and throat — oropharyngeal cancers.
Oropharyngeal squamous cell carcinoma (SCC) now easily surpasses cervical cancer as the most common HPV-associated cancer in the U.S., researchers confirmed in 2018, the CDC said.
There are vaccines to prevent hepatitis and HPV and antibiotics to treat Helicobacter pylori. If deployed broadly, vaccines and antibiotics could reduce new cancer cases in the future.
For more than a decade, HPV vaccination had been recommended for 11- to 12-year-old girls and young women up to age 26 not previously vaccinated. Since 2009, the vaccine also has been recommended for males ages 9 to 26.
But only around half of teens are getting the HPV vaccine, in part because physicians haven’t been recommending it. The CDC is pushing health care providers to recommend the vaccine, especially because it lowers cancer risks.
In late 2018, the US Food and Drug Administration approved the expanded use of the current HPV vaccine Gardasil 9, to include women and men ages 27 to 45.
Story ideas
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Find patient stories of those who have developed cancer from HPV and weren’t vaccinated. Check out some of these cases on the CDC website.
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Talk to doctors’ groups about why some health providers aren’t recommending the HPV vaccine
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How has the anti-vaccine movement impacted the ability to vaccinate individuals against these cancer-causing pathogens? Look into state legislative efforts to block HPV vaccination efforts
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Since antibiotics can eliminate H. pylori, how is rising antibiotic resistance impacting treatment? Is the bacteria developing resistance?
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With the rise of the opioid epidemic, might there be more cases of Hepatitis B and C and HIV? And could that mean more cancer cases down the road?
Articles
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Global burden of cancer attributable to infections in 2018: a worldwide incidence analysis: The Lancet Global Health, December 2019.
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How some viruses cause cancer: Verywell Health, November 2019.
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CDC: 92 percent of HPV-caused cancer could be prevented by vaccine: UPI.com, August 2019.
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Tips on reporting on the changing nature of HPV-related cancers: AHCJ, January 2019.
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7 viruses that cause cancer: MD Anderson, August 2018.
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Here’s how viruses inactivate the immune system causing cancer: ScienceDaily, March 2018.
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Vaccines that can prevent cancers: Manila Bulletin, February 2018.
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Human papillomavirus in cervical cancer and oropharyngeal cancer: One cause, two diseases: Cancer, June 2017.
CDC and data
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Reporters may find this CDC data visualization tool useful in localizing and personalizing stories on this topic. The tool provides state-by-state, gender-specific data for newly diagnosed HPV-associated oropharyngeal cancers, as well as HPV-associated cervical, vulval, vaginal, anal, rectal and penile cancers.
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In this chart, the agency offers a useful breakdown of data on HPV-related cancers by type, patient age and race.
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In addition to HPV-associated cancer statistics, the CDC also offers federal surveillance data on the prevalence of HPV and other sexually transmitted diseases.
Patient stories
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The voices of patient-advocates are augmenting awareness about the rise in HPV-related oropharyngeal cancers among men. When actor Michael Douglas told the Guardian newspaper that HPV, transmitted through oral sex, was responsible for his throat cancer, the news stirred tremendous controversy. It challenged taboos about discussing the sexual link to oropharyngeal cancers.
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What men should know about cancer that spreads through oral sex: Washington Post, April 2017
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Biotech executive and author Michael D. Becker used his personal story to bring attention to the toll of oral cancer-related HPV. Becker, who died of the disease in 2019 at age 50, believed the HPV vaccine would have saved him, Matthew Herper reported for STAT.
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In a Miami Herald feature, reporter Shayne Benowitz recounted the efforts of a local patient-advocate Jason Mendelsohn, who has used his treatment journey, to inform others about the disease.
Sources
Sharon Kuss-Duerkop, Ph.D., virology research instructor, University of Colorado Denver – Anschutz Medical Campus; a leading researcher on how infectious pathogens can cause cancer: sharon.duerkop@cuanschutz or 303-724-4224.
Researcher specializing in HPV and HPV vaccines., M.D., a scientist at the World Health Organization’s International Agency for Research on Cancer, and expert in the infectious disease connection to cancer: demartelc@iarc.fr.
Mona Saraiya, M.D., MPH, medical officer and team lead at the CDC’s Division of Cancer Prevention and Control’s Epidemiology and Applied Research Branch and an expert on HPV. The media contact is 404-639-3286.
Harrys Torres, M.D., associate professor of infectious diseases, MD Anderson Cancer Center, and an expert on cancer and infectious disease agents: HTorres@mdanderson.orgphone or 713-745-6839.
John T Schiller, Ph.D., deputy chief, Laboratory of Cellular Oncology, Center for Cancer Research at the National Cancer Institute, and a researcher specializing in HPV and HPV vaccines: schillej@mail.nih.gov or 240-760-7944.
