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Indiana Epidemiology Newsletter
Karen S. Gordon
ISDH Field Epidemiologist, District 10
Historically, the Ohio River has served as a primary transportation route for settlers and commerce, as farmers and manufacturers sent goods and crops on flatboats and barges downstream to the Mississippi River and eventually on to New Orleans. Today, the Ohio River continues to serve as a major artery for transporting bulk items such as coal and grain. However, the transport of people diminished with the arrival of railroads, improved highways, and air travel. Passenger transport along the river today is largely recreational aboard paddlewheel steamships. Marketing directors and visitor bureaus are trying to entice the ships to stop at their docks so the passengers can take arranged tours or side trips to benefit local businesses and attractions. River communities might consider the possibility of the passenger-laden boats bringing something with them other than the urge to shop. The city of Evansville and the Vanderburgh County Health Department learned this lesson when they received surprise guests in October 2006.
On October 20, 2006, news media reported that a riverboat had made an unscheduled stop in Owensboro, Kentucky, to send ill passengers to the hospital. The vessel continued on to its planned docking in Henderson, Kentucky, later that same evening, where additional sick passengers were transported to the local hospital. Henderson is served by the Green River District (KY) Health Department, and an epidemiologist and environmental director boarded the boat on Friday evening and accompanied passengers from Henderson to Paducah.
On October 22, 2006, a Vanderburgh County Health Department (VCHD) environmental health specialist notified the communicable disease director that, on October 21, approximately 150 passengers and crew of the affected riverboat were taken to an Evansville area hotel. The local fire department contacted the VCHD due to the increased requests for ambulance transport. Passengers who disembarked at Henderson included those in the same travel party as persons who had been hospitalized and anyone else who voluntarily wanted to end the cruise. After arrival at the hotel, some people became ill with vomiting and diarrhea.
The communicable disease director notified the health officer, the executive director, the ISDH district field epidemiologist, and the Indiana State Department of Health (ISDH) duty officer. The VCHD decision team met that afternoon and contacted Kentucky health officials and the Centers for Disease Control and Prevention (CDC). (The CDC had been unaware that riverboat passengers disembarking in Indiana had become ill.)
A team of four staff members from the VCHD and the ISDH district field epidemiologist arrived at the hotel with go-kits that included appropriate personal protective equipment (PPE) and needed materials. Since communication difficulties prevented using the CDC questionnaire, the team used a generic gastrointestinal survey tool. This decision proved good, as several guests went home the following morning, and the opportunity to interview them would have been lost.
Hotel staff gave the response team a printout of the roster of riverboat guests staying at the hotel. Four response team members went door-to-door to interview passengers and collect a stool sample if the individual was currently having diarrhea. Forty questionnaires were completed and forwarded to the CDC. The other member of the response team inspected the food service area and closed the pool. The ISDH Laboratories analyzed the stool specimens, which tested positive for norovirus by PCR. Through combined efforts, Indiana health officials were first to confirm the outbreak agent.
Control measures at the hotel included:
Self-isolation of sick or recovering passengers or crew to their hotel rooms (the hotel had already issued a written request to do this and encouraged use of room service)
Using disposable plates and eating utensils for room service and keeping trays in rooms
Providing plastic bags for soiled laundry and calling for immediate pick-up of laundry and room-service trays
Closing and superchlorinating the pool and hot tub and draining and disinfecting ice machines
Frequently disinfecting commonly touched surfaces throughout the hotel
Terminally cleaning the rooms of sick guests after checkout and leaving rooms vacant as long as possible
Excluding ill staff from work until 72 hours after symptoms stopped
Encouraging everyone to wash hands frequently with soap and water for at least 20 seconds
The VCHD conducted active surveillance by contacting hotel staff daily, Monday through Friday, for nearly three weeks (72 hours after cessation of symptoms in last reported case).
On October 26, VCHD staff met with the Vanderburgh County Emergency Management Agency (EMA), the hotel manager, and EMA and EMS officials from Henderson, Kentucky. The incident commander on the scene Friday evening when the riverboat first docked in Henderson reported that the captain and the cruise director would not follow some precautions and that the information coming from the boat was not consistent with information in the command center. It was unclear who had authority at the scene and whether that differed when the ship was on the river or when it was docked. The hotel manager reported no prior knowledge of the arrival of riverboat passengers. They came by bus to the hotel on October 21. According to the hotel manager, the cruise company decided to lodge the disembarked passengers in Evansville to facilitate flights out of the Evansville airport.
Vanderburgh County health officials responded within the target timeframe from the time they became aware of the public health threat. However, they were notified 24 hours after the threat arrived. The major points for improvement described in the after-action report included:
Lack of awareness of the Kentucky hospital and health department to notify Vanderburgh County health officials of transfer of persons exposed to an outbreak
Lack of awareness of an Indiana hospital to notify the VCHD of a request from a hotel to triage sick guests
Limited knowledge or lack of awareness at hospitals and in the hospitality industry of large-scale gastrointestinal outbreak control measures
These weaknesses were corrected by establishing an after-hours notification system (which was already under way), adding contact numbers for neighboring state and local agencies to the communication plan, and clarifying control measures and communication methods with central dispatch, hospitals, emergency response agencies, transportation agencies, hotels, cleaning companies and public health agencies of all five states involved in the outbreak (see below). Although no media arrived at the hotel while the response team was conducting interviews, it would have been beneficial to have a designated public information officer on site.
The incident involving passengers who stayed at a Vanderburgh County hotel was actually part of a larger norovirus outbreak that extended across multiple cruises of the same riverboat.
The CDC Vessel Sanitation Program investigates international cruise ship outbreaks when 3 percent of the passengers become ill. Ships without an international itinerary, such as domestic riverboats, fall under the authority of the Food and Drug Administration (FDA). Officially, the level of illness did not exceed 3 percent before the cruise left on October 18. This 7-day cruise originated in Pittsburgh with dockings scheduled in Cincinnati, Ohio; Louisville, Henderson, and Paducah, Kentucky; and Cape Girardeau, St. Louis, and Hannibal, Missouri.
On October 19, the CDC received a report from a passenger onboard the ship from October 14-18 who stated that passengers and crew members were ill. The next day, the riverboat company reported 30 passengers were ill, which exceeded 5 percent of the passengers. A CDC team, led by Dr. Anadi Sheth, met the riverboat in Paducah on October 22. The CDC team found that the vessel had two dining areas, three public bathrooms, a pool (which was closed), and no clinic or health care providers onboard. The crew had separate living and dining quarters. Many passengers were elderly, there was opportunity for frequent contact, and isolating ill passengers was difficult. Public restrooms were closed. Hand sanitizer was available at the front desk, dining area, elevators, and along handrails. Since the FDA inspection showed no violations, the ship was allowed to continue its journey. Illnesses continued, so there was an early termination of the cruise in Cape Girardeau, Missouri. Ill passengers were either hospitalized or sent to hotels, and well passengers were bused to St. Louis for lodging. An action plan was prepared for the next cruise. The crew docked the riverboat at St. Louis, where it was cleaned and inspected by the FDA. Passengers embarking were given an educational presentation about the illness. A nurse and FDA representatives were onboard when the boat left on October 24. Again, reports of ill passengers and crew surfaced, and the CDC team met the ship in Hannibal. The FDA issued a stop-sail order, all non-essential crew members were removed, and the next cruise was canceled. A new action plan was developed, and no illness was reported on the subsequent cruise.
Seventeen passengers from three consecutive cruises tested positive for the same strain of norovirus, a new variant known as GII.4. According to the CDC, during the cruise with passengers diverted to Vanderburgh County, 52 percent of the passengers and 18 percent of the crew members became ill (43% of total ship population). According to Dr. Sheth, secondary cases were noted in 9 hotel employees, 5 public health responders, 2 health care workers, 3 cruise company employees, and 2 other individuals. No secondary cases arose among the VCHD or ISDH district staff.
Several conclusions were made during the investigation. The source of the initial infection was unknown. Infection was most likely transmitted person to person, and several secondary cases were identified. Transmission continued despite cleaning and isolation measures, demonstrating the environmental hardiness of norovirus (see below). Guidelines, similar to those for ocean-going vessels, are needed for outbreak reporting and control on domestic ships.
Norovirus is the most common cause of acute infectious gastroenteritis. Studies show that common settings for norovirus outbreaks include restaurants and catered meals (36%), long-term care facilities (23%), schools (13%), and vacation settings or cruise ships (10%). Person-to-person transmission among closed populations is common. The incubation period is usually between 24 and 48 hours, and symptoms, which generally last 24 to 60 hours, include sudden onset of vomiting, watery non-bloody diarrhea, abdominal cramps, and nausea. Recovery is usually complete but there is a risk of dehydration. Noroviruses are highly contagious, and as few as 10 viral particles may be sufficient to cause infection. Noroviruses are transmitted primarily through the fecal-oral route, either by consumption of fecally contaminated food or water or by direct person-to-person contact. Environmental and fomite contamination may also serve as a source of infection. Several modes of transmission may occur during outbreaks.
On May 18, 2007, the FDA Office of Regulatory Affairs awarded the Group Recognition Cross-Cutting Award to a group of 53 federal, state, and local health officials, including Denise Cory of the Vanderburgh County Health Department, for their successful coordination during outbreak investigation. Agencies recognized included the CDC, Coast Guard, FDA, and the state health departments of Illinois, Indiana, Kentucky, Missouri, and Ohio.
Denise Cory, Director of Communicable Disease Control, Vanderburgh County Health Department, provided background information and a summary of the VCHD after-action report.