The phone rang in the middle of the night. "John, do you know what time it is?" "Sorry but I feel terrible and wanted to know if you're okay." When we arrived at Urgencias the duty doctor knew exactly what to do when he learnt we had eaten ceviche earlier. After a period of observation he extracted the anisakis parasites from John's stomach by endoscope. We were having coffee a few hours later, he none the worse for the experience and lucky to have found a doctor who was on the ball.
There are two main dangers that can make the ingesting of this fish parasite dangerous: if the person is allergic or if the doctor does not act quickly. The anisakis worm lives in fish, so a human host is a cul-de-sac and it dies as it tries to penetrate the stomach wall. Immediate extraction, before it passes into the intestine, is the best solution. So, while John was lucky with his prompt examination, many people are not, and can spend months undergoing medical treatment as a result of infection. There are no reported deaths.
Probably the unhappiest aspect is that people affected, even briefly, swear off fish for life. This is like giving up driving because you have an accident. The chances of history repeating itself are exactly the same as if you had never experienced it. Anyone may be affected the next time they eat fish, regardless.
Official guidelines recommend (and compel in the case of restaurants) the fish to be deep frozen for five days, although cooking at very high temperatures allegedly has the same effect. It is unlikely a restaurant will serve sushi, sashimi, ceviche, anchovies in vinegar, salmon roe, smoked fish, etc, that were not frozen adequately beforehand. But look at the numbers. In Spain there are no more than 150 reported cases annually, compared with Japan's 1,000. Other Mediterranean countries have almost zero cases, and most of Spain's occur on the Atlantic coasts, leading to the conclusion that for the average Costa resident or visitor, the chances of becoming a victim are remote. A week later John and I were eating lubina a la sal in the same restaurant.