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I make sushi often, and i never use sushi-grade fish...i simply buy fresh fish from the market. I know the requisites of frozen for 20 hours etc., but I know for sure there are many restaurants in europe that certainly do not (exclusively) use frozen fish. Moreover, I ate sushi often in the years I lived in Thailand, and well...pretty sure they use non frozen either. Never a problem, but, I realise that this does not prove anything..

Does anyone have an idea of the size of the risk, i.e. the incidence of parasite infection after eating non-frozen fish raw? I am asking after research..i cannot really find it.

These articles were informative, but no info on size of risks: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3374688/ http://cid.oxfordjournals.org/content/41/9/1297.full

This study gives a bit more information: http://cmr.asm.org/content/23/2/399.full

"During 1973 to 2006, 188 outbreaks of seafood-associated infections, causing 4,020 illnesses, 161 hospitalizations, and 11 deaths, were reported to the Food-Borne Disease Outbreak Surveillance System. Most of these seafood-associated outbreaks (143 [76.1%]) were due to a bacterial agent; 40 (21.3%) outbreaks had a viral etiology, and 5 (2.6%) had a parasitic cause (Table 1)"

Now, considering this is not concentrating on raw fish only, but all fish consumption, I would say the chances of getting sick from eating raw fish with a parasite are microscopically tiny? Agreed?

Is there someone who could get me this report: this seems to be the basis of the safety measures

American Gastroenterological Association. 2000. Determination of the incidence of gastrointestinal parasitic infections from the consumption of raw seafood in the U.S. [Report under FDA Contract 223-97-2328 with Life Sciences Research Office, American Society for Nutritional Sciences]. AGA, Bethesda, MD.

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I have no idea what the risks are, but years ago, when I wasn't feeling well, I had some blood tests done, and they found something swimming in there. Of course, I not only had sushi, but also Ethiopian food. (raw beef). So it's possible that it wasn't caused by the sushi, but I'm still going to assume that there's some risk, even if it's low. – Joe Jan 16 at 19:21
    
Sorry to hear that, but this sort of anecdotical one-person story is really not what I am after... unless I can have say 1000 sushi eaters and 1000 non sushi eaters and compare...is there way to do this here? – Marc Luxen Jan 16 at 20:03

As I explained in another question recently, there is no meaningful answer to this. There is no way to make the prediction "you have a X percent chance of infection per parasite infested meal". Instead of predicting it mathematically, we could feed people infected fish and measure it, but as far as I am aware, no ethical board will approve that experiment.

Also note that beside the type of study you found (listing every single type of infection), there are also studies which take a more epidemiological point of view. They still don't attempt to give the kind of number you requested. That's another good sign that this answer does not exist - if it did, I'd expect these experts to have found it and incorporated it in their articles.

The best you can have is circumstantial data. For example, Phan et al. 1 sampled the incidence of trematodes in fish from a certain river. You can try extrapolating a chance that a parasite is present in your fish, although of course this depends on region where the fish was caught and on treatments applied during raising (e.g. preventive medicine or food type in fish farms) and after catching (freezing the fish). I am not aware of a resource which covers parasite incidence in all types of fish, but single studies can give you a starting point. The fish investigated in Phan's study for example had trematode infestation rates between 50% and 80% for the different species (and they did not look for other types of parasite).

Another statistic you can use: the prevalence of fish transmitted infections in countries where raw fish consumption is common. That's again not a reflection of your own personal risk, just a data point. One such statistic is for example:

An estimated 20% of immigrants from southeast Asia to Europe or North America have fish borne trematode infections. In highly endemic areas, such as northeast Thailand, the prevalence of O. viverrini may reach 90% 2


A source which won't give you a numeric answer, but classifies risk as "significant" or "not" is published by the FDA. But as a consumer, you will probably not have the information needed to find out if you fall into the "not significant" category, or the equipment to do the processing recommended for unsafe fish. It is a government regulation, Fish and fishery products hazards and control guidance, chapter 53. Still, if you're looking for actual cooking practices beside the exact information you requested, it's probably interesting for you.

1 Phan VT, Ersbøll AK, Bui TQ, Nguyen HT, Murrell D, Dalsgaard A. Fish-Borne Zoonotic Trematodes in Cultured and Wild-Caught Freshwater Fish from the Red River Delta, Vietnam. Vector Borne and Zoonotic Diseases. 2010;10(9):861-866. doi:10.1089/vbz.2009.0134.

2 Deardorff, Thomas L. "Epidemiology of marine fish-borne parasitic zoonoses." Southeast Asian J Trop Med Public Health 22.suppl (1991): 146-149.

3 FDA. Fish and Fishery Products Hazards and Controls Guidance. Gainesville 2011.

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I know it's more of a related question, but is there a meaningful answer in the context of sushi-grade fish or sushi restaurants? Seems a little more possible to study, and a little more reasonable for agencies to care about. – Jefromi Jan 16 at 18:52
    
@Jefromi see cooking.stackexchange.com/questions/723/…. "sushi grade" is a marketing term. The procedures for making fish sufficiently safe for the FDA are outlined in the regulation I mentioned. They are more of the "if there is more than zero chance of parasite, freeze and then eat the fish including the now-dead parasite" kind. They don't care to put a number to the chance of getting ill after eating unsafe fish. – rumtscho Jan 16 at 18:58
    
Thanks for this excellent answer. Iam still digesting and thinking, will come back to that.I am not so much concerned about my personal safety, but more about the rationale behind those safety measures. In the EU, and even more in the US, we have become risk-avoiding to the extreme, for which we pay a high price in terms of money, time, and freedom. If eating raw fish result in one in million consuption in a perfectly treatable infection, those measures are over the top. If it results in 1 in 1000 in a life threatening infection, they are not. And I just dont have the knowledge to decide.. – Marc Luxen Jan 17 at 9:05
    
updated the information in the question. Would love to hear your opinion.. – Marc Luxen Jan 17 at 20:23

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