Don't eat raw freshwater fish or shrimp such as yusheng (鱼生), sashimi, raw-fish congee or drunken shrimp; if you have often eaten them, get checked once for liver flukes, and if found, take praziquantel as your doctor says

Cost

Not eating raw fish costs nothing; the hard part is breaking a taste of many years and turning it down at group meals. If you have often eaten it, go to a hospital for one stool test for eggs, and the cost varies by place. If found, take praziquantel at the dose your doctor prescribes, usually for 1 to 2 days.

What you get

Clonorchis sinensis is commonly called the liver fluke. The International Agency for Research on Cancer (IARC), part of the World Health Organization, met in 2009 and concluded that long-term infection with it causes cancer in humans. It causes bile duct cancer and is listed as Group 1. The 1994 evaluation had given only Group 2A (probably carcinogenic). Pooling published studies, people infected with liver flukes had about 4.8 times the risk of bile duct cancer. As reported: relative risk 4.8 (95% CI 2.8–8.4, the plausible range). This number also counts another liver fluke in Southeast Asia. In the same paper, hepatitis B was 2.6 times and hepatitis C 1.8 times, and the liver fluke was the strongest of the three. Another paper pooled 36 studies. In case-control studies, bile duct cancer was about 4.37 times (OR 4.37, 2.84–6.72). In follow-up studies it was about 10.43 times (RR 10.43, 2.90–37.47). Cholangitis and cholecystitis were about 7.80 times (RR 7.80). Gallstones were about 2.42 times (RR 2.42). Hepatocellular carcinoma was about 4.69 times (OR 4.69). No significant link was seen with cirrhosis. The heavier the infection, the more of these diseases. In a national survey in 2014 to 2015, the infection rate was 0.47%, about 6,000,000 (600万) people. The four provinces with an infection rate over 1% were Guangdong, Guangxi, Heilongjiang and Jilin. Estimated from 2016 to 2021 surveillance data, the 2020 national rate was about 0.67%, about 9,460,000 (946万) people. Of that, Guangxi was about 8.92% and Guangdong about 2.99%. In 2024, 15 departments including the National Disease Control and Prevention Administration (国家疾控局) issued a prevention and treatment program. It took the average infection rate at surveillance sites in 2018 to 2022 as the baseline. Guangxi was 8.75%, Jilin 4.38%, Heilongjiang 3.16% and Guangdong 2.95%. The China National Center for Food Safety Risk Assessment (国家食品安全风险评估中心) advised in 2026 that seasonings such as liquor, vinegar and wasabi cannot effectively kill liver flukes. Freezing has to be at minus 20℃ or lower for at least 7 days straight. Heating has to bring the center of the food to at least 70℃ and hold it for at least 10 minutes. The International Agency for Research on Cancer also states that pickled or smoked freshwater fish can still transmit it. For treatment, a 2022 pooled analysis covered 26 trials and 3340 people. The World Health Organization's recommended praziquantel regimen is 25 milligrams per kilogram of body weight each time, 3 times a day, for 2 days. The predicted cure rate for Clonorchis sinensis is 98.5% (85.4%–99.9%).

Notes

The risk numbers above all come from case-control and follow-up studies, with no assigned comparison groups. No study has directly compared whether “testing and then treating” means fewer bile duct cancers. Bile duct cancer is rare to begin with, so although the multiple is high, the extra risk to any one person is not large. The evidence grade is therefore B. About 4.8 times compares infected with uninfected people; it is not how much disease this practice prevents, so the size of the benefit was set at medium on judgment, the same way as §2.46 (throw out moldy food, the whole bag). Guangdong's Center for Disease Control says liver flukes can live in the human body for 20 to 30 years. Mild infections often have no symptoms, so people who often eat raw fish shouldn't wait until they feel unwell to be checked. A stool test for eggs is the way to confirm; ultrasound, CT and blood tests can only assist. Praziquantel must be dosed by a doctor according to body weight and how heavy the infection is. The Institute of Parasitic Diseases (寄生虫病所) states that where cysticercosis exists, the history should be asked about before using a high dose. If you are cured and go back to eating raw fish, you will be infected again. Keep the knife and cutting board for raw fish separate from those for cooked food. The parasites common in raw saltwater fish sashimi are others, such as Anisakis; the Hong Kong Centre for Food Safety advises buying from licensed shops, and that older people, children and pregnant women should not eat raw fish. Infection in children affects their growth. Hepatitis B and hepatitis C also harm the liver and cause cancer; see §1.14 (get the hepatitis B two-and-a-half tests) and §1.45 (get one hepatitis C antibody test). The beneficiary of this item is mainly you and the family who eat with you.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans (2012). Opisthorchis viverrini and Clonorchis sinensis. In: Biological Agents. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 100B, 341-370. https://publications.iarc.who.int/119
2. Shin HR, Oh JK, Masuyer E, 等 (2010). Epidemiology of cholangiocarcinoma: an update focusing on risk factors. Cancer Science, 101(3), 579-585. https://doi.org/10.1111/j.1349-7006.2009.01458.x
3. Xia J, Jiang SC, Peng HJ (2015). Association between liver fluke infection and hepatobiliary pathological changes: a systematic review and meta-analysis. PLoS ONE, 10(7), e0132673. https://doi.org/10.1371/journal.pone.0132673
4. Qian MB, Chen J, Bergquist R, 等 (2019). Neglected tropical diseases in the People's Republic of China: progress towards elimination. Infectious Diseases of Poverty, 8, 86. https://doi.org/10.1186/s40249-019-0599-4
5. Qian MB, Huang JL, Wang L, 等 (2025). Clonorchiasis in China: geospatial modeling of the population infected and at risk, based on national surveillance. Journal of Infection, 91(1), 106528. https://doi.org/10.1016/j.jinf.2025.106528
6. 国家疾控局等 15 部门 (2024). 关于印发全国包虫病等重点寄生虫病综合防治实施方案（2024—2030 年）的通知，附表 7. https://www.gov.cn/zhengce/zhengceku/202405/content_6950309.htm
7. 国家食品安全风险评估中心 (2026). 关于慎食淡水生鲜食品预防肝吸虫病的风险提示（重庆市疾病预防控制中心转载）. https://www.cqcdc.org/index.php?a=shows&catid=179&id=3861
8. Qian MB, Patel C, Palmeirim MS, 等 (2022). Efficacy of drugs against clonorchiasis and opisthorchiasis: a systematic review and network meta-analysis. The Lancet Microbe, 3(8), e616-e624. https://doi.org/10.1016/S2666-5247(22)00026-X
9. 中国疾病预防控制中心寄生虫病预防控制所 (2020). 华支睾吸虫病（肝吸虫病）防治知识（广东省疾病预防控制中心转载）. https://cdcp.gd.gov.cn/jkjy/jkzt/jscbfz/content/post_3439516.html
10. 广东省疾病预防控制中心 (2023). 吃鱼生没余生？警惕潜伏在鱼生中的“凶手”肝吸虫！ https://cdcp.gd.gov.cn/jkjy/jkts/content/post_4274108.html
11. 香港食物安全中心. 淡水鱼刺身的食物安全. https://www.cfs.gov.hk/sc_chi/multimedia/multimedia_pub/multimedia_pub_fsf_148_01.html

Translated from the Chinese original. Original book, section 2, tip 47. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer