On April 26, 2013, the Southern Nevada Health District (SNHD), Office of Epidemiology (OOE) received reports of gastrointestinal illness from 8 independent groups of patrons of Firefly on Paradise or the adjacent affiliated restaurant Dragonfly on Paradise (Firefly) located at 3900 Paradise Road, Las Vegas, NV 89109. All patrons from these groups ate at the restaurant during April 21-24, 2013. Ill patrons reported symptoms of diarrhea and/or vomiting after they consumed food from Firefly restaurant, and many sought medical care for their illness. In response to these illness reports, the SNHD initiated an investigation.

On April 26, 2013, the SNHD performed investigative inspections and closed Firefly and Dragonfly restaurants to minimize ongoing risk of illness.

A probable case is defined as illness in a person who consumed food served by Firefly restaurant during April 21-26, 2013, experienced diarrhea (defined as ≥ 3 bouts of loose stools) and/or ≥ 1 episodes of vomiting during a 7-day period after eating, and reported the illness to SNHD no later than end of day May 13, 2013 (midnight). The case definition for confirmed cases is a positive Salmonella stool culture.

The epidemic curve as of May 20, 2013 is presented in the figure below and shows a total of 294 people whose illnesses met the case definition (73 confirmed and 221 probable cases). All identified ill persons ate at Firefly during April 21 through April 26, 2013. Illness onset dates occurred within the April 22 to May 1, 2013 time frame.

From various surveillance data sources, we have received reports of illness from restaurant patrons who normally reside in 27 states and 2 foreign countries (Canada and United Kingdom) who ate at Firefly during their visits to Las Vegas.

Of the 21 food items that were analyzed, one item, cooked chorizo (a type of sausage), tested positive for Salmonella. Culture and PFGE-pattern results of the Salmonella isolate obtained from the cooked chorizo matched those of the outbreak strain.

Initially, SNHD and OOE attempted to trace back some food products that either arrived raw to the restaurant or were served uncooked to patrons to try to identify how a food could have become contaminated at its source or during delivery, storage or preparation. However, in light of the laboratory result that the outbreak strain of Salmonella was isolated from the cooked chorizo, trace-back efforts have been redirected at the chorizo products due to a small possibility that raw chorizo was contaminated prior to arriving at Firefly.

As of May 20, 2013 at least 290 patrons and 4 employees who consumed food and/or drinks at Firefly restaurant during April 21-26, 2013 have been identified to be confirmed or probable cases of Salmonella infection. No illness has been reported among staff or patrons of the other Firefly restaurants located in Clark County (Firefly Westside and Firefly on Eastern). The rate of cases being reported to SNHD has declined significantly with no evidence of any disease transmission after the closure of the restaurant on April 26, 2013. It is possible that the number of cases will change slightly over the next weeks as the last laboratory results arrive that either identify new confirmed cases, or eliminate probable cases from our count should they fail to have PFGE patterns matching the outbreak strain.

No concurrent cases of salmonellosis having a PFGE pattern matching the outbreak strain have been identified in the U.S. other than those linked to the Firefly on Paradise restaurant.

It is likely that the outbreak was due to local cross-contamination in the restaurant’s kitchen and not from a contaminated commercial food.