REPORT / INTERNATIONAL NEWS

On July 12, 2011, a New York City man sat down at a Manhattan restaurant and made what seemed like a healthy dinner choice: grouper.

The man was physically fit and just the day before had gone for a two-mile swim.

But hours after his meal, he could barely walk.

It turned out his grouper was contaminated by a colorless, odorless, tasteless toxin that can cause a type of fish poisoning called ciguatera and can produce symptoms that include dizziness, vomiting and cramps. He was one of 28 New Yorkers to fall ill from ciguatera between August 2010 and July 2011 — more cases than had been reported in the entire preceding decade in the city, according to a report released on Thursday by the Centers for Disease Control and Prevention.

The reason for the spike is not exactly clear, the report said, but “it might reflect changing sources and diversity of fish species marketed� in the city and elsewhere.

The report highlights the detective work done by city agencies to trace the cause of the outbreaks and stem any further spread.

The toxins that lead to ciguatera are most commonly found in coral reef fish like barracuda, grouper, snapper, amberjack and surgeonfish. But it is not easy to identify contaminated fish before they are consumed.

Testing fish for the presence of the toxin before it reaches the market is not feasible, according to the report, and there is no rapid field test that inspectors can use once the fish is being sold in restaurants or stores.

The report focuses on six outbreaks and one individual case reported to New York health authorities in 2010 and 2011. In those cases, the symptoms experienced by the victims were varied, including gastrointestinal, cardiovascular and neurological problems.

Investigators did not release the names of patients, vendors and fish distributors. Because the toxin is not easily detectable, there was no suggestion any of the vendors that sold toxic fish did anything wrong.

The first case was reported on Aug. 6, 2010, when a 16-year-old girl and her 47-year-old mother went to a hospital emergency room after experiencing diarrhea, lightheadedness and perioral tingling — which is a “pins and needles� feeling around the mouth and lips. They had eaten barracuda bought at a Queens fish market.

Hours later, the report said, an additional four relatives, “who had eaten the same fish, reported tingling in their extremities.�

The victims were experiencing dizziness, headache, faintness and vomiting, and doctors struggled to figure out what was causing the symptoms.

Since all the victims ate barracuda bought from the same market, the doctors suspected the fish as being the most likely culprit. They alerted the city’s Poison Control Center, which alerted the city’s health department.

Samples of the barracuda were collected from the patients’ home and the fish market, and sales of barracuda at the market were ordered suspended.

Tests performed at a federal Food and Drug Administration laboratory confirmed the presence of ciguatera.

Over the next month, an additional seven cases of ciguatera were reported and traced to barracuda bought from fish markets in three boroughs and one restaurant.

The next outbreak was reported on Nov. 19, 2010, when 11 people from three families fell ill after eating fish that was bought at a Queens supermarket that was labeled grouper.

The final outbreaks in the report occurred on July 12, 2011, when an additional four people fell ill after eating grouper at a Manhattan restaurant. The majority of patients with ciguatera experience symptoms within 6 to 48 hours, and essentially, the report said, patients are treated according to the best care practices for each symptom.