The short answer
Liver flukes are parasites caught from raw or undercooked freshwater fish. Long-term infection is linked to bile-duct cancer, mainly in parts of Asia. Cooking fish thoroughly prevents infection.
Liver flukes is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by eating raw or undercooked freshwater fish in affected regions.
It is most strongly linked to bile-duct cancer (cholangiocarcinoma).
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
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The full explanation.
The simple version
Liver flukes are small parasitic worms. People can pick them up by eating raw or undercooked freshwater fish. Over many years, infection can inflame the bile ducts and lead to a cancer there. This is most common in parts of Southeast Asia and East Asia.
What liver flukes are
Two liver flukes are classified as carcinogenic to humans. They are Opisthorchis viverrini and Clonorchis sinensis. People become infected by eating raw, pickled, or undercooked freshwater fish that carries the parasite. The fluke then lives in the bile ducts.
How people are exposed
Common ways people come into contact with them:
- Eating raw, pickled, or undercooked freshwater fish in endemic regions.
- Traditional dishes made with uncooked fish.
- Repeated infection over years, which raises risk.
The cancer connection
Long-term liver-fluke infection is linked to cholangiocarcinoma. That is a cancer of the bile ducts.
IARC places liver flukes in Group 1, carcinogenic to humans. Group 1 is the strongest evidence category. It means there is enough evidence that they can cause cancer in people. IARC is the cancer agency of the World Health Organization.
Hazard is not the same as risk
Hazard and risk are easy to mix up. Calling liver flukes a carcinogen is a statement about hazard. Hazard means they can cause cancer under some conditions. That is not a statement about your personal risk. Risk depends on how much you are exposed to, for how long, and other factors. Agents that share a group can still differ hugely in the risk they pose day to day. The label answers whether something can cause cancer. It does not say how likely that is for you.
How to lower your exposure
- Cook freshwater fish thoroughly before eating it.
- Avoid raw or pickled freshwater fish in endemic areas.
- Treat known infections with medication.
If you are looking at your overall cancer risk, small, steady steps add up. To see where liver flukes sits among all the things that affect cancer risk, read our overview of cancer prevention and what raises cancer risk.
The bottom line
Liver flukes are known human carcinogens (IARC Group 1). The most useful step is knowing where exposure comes from. Take reasonable steps to reduce it, without losing sleep over a single label. Put your energy into the biggest risks you can control.
Words to know
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Common questions
Does liver flukes cause cancer?
Yes. Liver flukes is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to liver flukes?
Most exposure happens by eating raw or undercooked freshwater fish in affected regions.
Which cancers are linked to liver flukes?
It is most strongly linked to bile-duct cancer (cholangiocarcinoma).
How can I reduce my exposure to liver flukes?
The main steps are cooking freshwater fish thoroughly.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether liver flukes can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
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Last updated: 2026-08-10Next planned review: 2028-07-05
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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