Cancer

Viruses and other infections that cause cancer, and why every adult should get hepatitis B and C screening

About 1 in 8 cancers worldwide are caused by viruses and other infections. Hepatitis B and C screening is the step every US adult is advised to take once.

Published

October 5, 2026

Read time

8 min read

Medically reviewed by

Rhonda Collins, FNP-C

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About 1 in 8 new cancers worldwide are caused by an infection, according to a study published by the World Health Organization’s cancer agency in September 2026. Five infections, four viruses and one bacterium, account for almost all of them. For most US adults, the clearest single step is one you may not have taken yet: a one-time blood test for hepatitis B and hepatitis C, which the CDC advises for every adult aged 18 and older.

Hepatitis C is curable. Hepatitis B can be managed with treatment and monitoring, and prevented by vaccine. Many people with either infection do not know they have it, which is why the test matters.

The new estimate: 2.3 million infection-caused cancers a year

The International Agency for Research on Cancer (IARC) estimates that about 2.3 million new cancer cases worldwide in 2024, about 12% of all new cases, were caused by infections. The figures come from a study by Rumgay and colleagues published in The Lancet Oncology on 28 September 2026, and are summarized in IARC press release No. 387.

The study looked at 12 infectious agents known to cause cancer in humans. Five of them account for almost all infection-caused cancers, per the IARC release:

The burden is uneven. More than three quarters of infection-related cancers occurred in low- and middle-income countries, and Eastern Asia alone accounted for 42%, largely driven by H. pylori and hepatitis B, according to the IARC release.

Which cancers each infection is linked to

The US National Cancer Institute summarizes the cancers each of these infections can cause in its overview of infectious agents and cancer:

• H. pylori: noncardia gastric cancer (a type of stomach cancer) and gastric MALT lymphoma, a lymphoma of the stomach lining.
• HPV: nearly all cervical cancers, most anal cancers, and many oropharyngeal (throat), vaginal, vulvar, and penile cancers.
• Hepatitis B and hepatitis C: liver cancer, after long-term (chronic) infection.
• EBV: certain lymphomas and cancers of the nose and throat. The IARC release adds that EBV also contributes to a proportion of gastric cancers, one reason it now ranks ahead of hepatitis C.

Why most of these cancers are considered preventable

IARC states that most infection-related cancers can already be prevented with well-established public health measures. The release lists them:

• vaccination against HPV and hepatitis B;
• testing and treatment for H. pylori and viral hepatitis;
• HIV prevention and care;
• screening programs for HPV-related cancers.

None of these works by itself. A test only helps when a positive result leads to treatment, monitoring, or vaccination. For EBV, IARC notes that effective vaccines are not yet available.

For a US adult, two of these tools are already part of routine care for everyone: a one-time hepatitis B test and a one-time hepatitis C test.

Hepatitis B and C testing: what the CDC recommends for every adult

The CDC recommends that all adults aged 18 and older be tested for hepatitis B and hepatitis C at least once in their lifetime, whether or not they have symptoms or known risk factors.

The reason is simple: these infections are often silent. According to the CDC, more than half of people with hepatitis B and nearly one in three people with hepatitis C are unaware of their infection. About 75% to 85% of people with hepatitis C have no symptoms, the CDC notes.

The hepatitis B triple panel, in plain language

The CDC’s 2023 hepatitis B recommendation calls for a triple panel: three blood markers read together.

• Hepatitis B surface antigen (HBsAg): a piece of the virus itself. A positive result means the virus is in your blood now.
• Hepatitis B surface antibody (anti-HBs): the antibody your immune system makes after vaccination or after clearing the virus. It points to immunity.
• Total hepatitis B core antibody (total anti-HBc): an antibody made only after contact with the actual virus, never from the vaccine. It shows a current or past infection.

Reading the three together is what separates an active infection from a past one, and both from vaccine protection.

The hepatitis C test: antibody first, then RNA

Hepatitis C testing starts with an antibody test. If the antibody is reactive, a second test looks for the virus’s genetic material (HCV RNA). Antibodies can stay after the infection has cleared, so only the RNA test shows whether the virus is still there.

The CDC also recommends hepatitis C testing during every pregnancy, and periodic testing for people with ongoing risk, such as people who inject drugs and share equipment or people on maintenance hemodialysis.

How the USPSTF recommendations differ

The US Preventive Services Task Force (USPSTF) has slightly different guidance:

• Hepatitis C: screen all adults aged 18 to 79 (2020, grade B).
• Hepatitis B: screen adolescents and adults at increased risk of infection (2020, grade B). This is a risk-based recommendation, not a universal one.

The CDC’s universal hepatitis B recommendation is broader. Following it means adults without a known risk factor get tested too.

What your hepatitis results mean, and what happens next

Hepatitis B results

The CDC interprets the triple panel in a few common patterns:

Other combinations exist and need follow-up testing to sort out. If all three markers are negative, you have never been infected and are not protected, and the CDC describes hepatitis B vaccination as the best way to prevent infection.

If you have chronic hepatitis B, several antiviral medicines are approved. They control the virus but, according to the CDC, do not cure it, so people who start treatment may need it long term. Not everyone with chronic hepatitis B needs medication. The CDC advises having your liver checked regularly, every 3 to 6 months.

Hepatitis C results

• Antibody nonreactive: no hepatitis C infection, unless you had a very recent exposure.
• Antibody reactive, RNA not detected: a past infection that has cleared.
• Antibody reactive, RNA detected: a current infection, and the CDC recommends treatment.

Hepatitis C is treated with antiviral medicines. The CDC states that treatment cures more than 95% of people in 8 to 12 weeks.

A positive hepatitis B or C result is the start of care, not the end of it. Review it with a clinician who can order the next tests and, if needed, refer you to a liver specialist.

How Mito covers the one-time screen in a single blood draw

Mito’s Hepatitis Panel (A, B, C) with Reflex Testing is a Quest Diagnostics panel (test code 6462) that covers the CDC’s one-time adult screen in one draw:

• the full hepatitis B triple panel: surface antigen (with confirmation of a positive result), surface antibody, and total core antibody;
• hepatitis C antibody, with automatic reflex to a quantitative HCV RNA test when the antibody is reactive or borderline, so you do not need a second visit to find out whether an infection is current;
• hepatitis A total antibody, which shows past infection or vaccination for hepatitis A.

One limit to know: the hepatitis B surface antibody on this panel is qualitative. It reports whether antibody is present, not a numeric level. It does not confirm a specific protective titer. If you need a documented antibody level, for example for a job or school requirement, ask for a quantitative anti-HBs test.

H. pylori and HPV in brief

H. pylori

H. pylori is the single largest infectious cause of cancer worldwide in the IARC estimate. Unlike hepatitis B and C, it is not part of a universal screening recommendation for US adults. Testing is usually done when there are symptoms of gastritis or ulcers, such as upper abdominal pain, bloating, early fullness, or nausea, or to confirm that a past infection was cleared after treatment, per MedlinePlus.

Breath and stool tests detect a current infection. A blood antibody test cannot reliably tell a past infection from a current one. Our guide on how to test for H. pylori compares the options, and Mito offers an H. pylori urea breath test.

HPV

HPV causes nearly all cervical cancers. Two tools address it:

• Vaccination. The CDC recommends HPV vaccination at ages 11 to 12 (it can start at 9), with catch-up through age 26. Some adults aged 27 to 45 who were not fully vaccinated may decide on it with their clinician.
• Cervical screening. The USPSTF recommends a Pap test every 3 years from ages 21 to 29. From 30 to 65, the options are a Pap test every 3 years, HPV testing every 5 years, or both together every 5 years. Mito offers a Pap and HPV DNA co-test.

The bottom line

Infections cause about 1 in 8 cancers worldwide, and most of those cancers can be prevented with tools that already exist. For US adults, the step that applies to everyone is a one-time hepatitis B and hepatitis C test. If you have never had one, or are not sure, a single hepatitis panel answers both questions and shows whether you are protected against hepatitis B.