The first Shigella illness involving a guest of the Doubletree Hotel was reported to the Colorado Department of Public Health and Environment (CDPHE) on September 9, 2003. Interviews with other persons confirmed that multiple people had been ill during or following their stay at the hotel. On September 11, CDPHE notified the Foodborne and Diarrheal Diseases Branch of the federal Centers for Disease Control and Prevention (CDC) of a cluster of diarrheal illness among guests of the hotel. On September 12, CDC staff left Atlanta for Denver, to assist the CDPHE and Tri-County Health Department in their investigation of the outbreak. See CDC Investigation Report, dated September 13, 2004.
A comprehensive questionnaire was developed, guest lists were obtained, and interviews conducted as part of the outbreak study. Two separate large groups of hotel guests were identified. One group consisted of a wedding party, and the second consisted of a World War II veterans reunion, with attendees from a number of different states. Members of both groups, as well as a random sample of hotel guests, were contacted and interviewed.
For purposes of the investigation study: “A case was defined as a person with gastrointestinal illness characterized by three or more episodes of diarrhea in a twenty-four hour period or having both fever and abdominal cramps since staying at or attending an event at Hotel A [the Doubletree Hotel] during the exposure period from September 4 to September 7.”
A statistical analysis was conducted of risk factors, exposures, symptoms and attack rates. Ill persons were instructed to seek medical care and to test stool cultures. An investigation was conducted of the hotel kitchen and staff food handlers. 132 persons were interviewed as part of the study.
Laboratory testing ultimately identified ten culture-confirmed cases of Shigella sonnei infections, three of whom were foodhandlers working in the kitchen during the outbreak. An investigation of the hotel kitchen was conducted on September 15, finding no violations. On September 17, the hotel manager agreed to voluntarily close the kitchen and food facilities, due to a “potential Shigella outbreak”; the kitchen was reopened on September 18.
Once the investigation was concluded, the report identified the following critical outbreak findings:
- an outbreak of Shigella sonnei had occurred among guests and employees of the hotel;
- epidemiologic and environmental evidence implicated the honeydew melon served at the breakfast buffet;
- there was no evidence of hotel staff contaminating the honeydew melon;
- contamination likely occurred during the period of September 4-7, and likely occurred over a period of a few days;
- some practices by the kitchen food handlers were not optimal; and
- the honeydew melons were traced back to two farms in California, but the investigation was inconclusive as to the possible source of contamination at those farms.
The CDC report, in part, also recommended that the hotel adopt the following procedures: hotel food handlers should not prepare or serve food if ill; preparation of raw fruits should minimize contamination from the peel or rind; employees should be trained to monitor food temperatures; employees should wash their hands thoroughly; and food service training should be required of restaurant staff.