CDC Boards Cruise Ship to Investigate Potential Norovirus Outbreak

Royal Caribbean’s 138,000 ton cruise ship, Explorer of the Seas, left the port of Bayonne, New Jersey on January 21, 2014, beginning a ten-day itinerary that included stops at several islands in the Caribbean.  A few days into the voyage, passengers became ill at an alarming rate. Staff from the Centers for Disease Control (CDC) were flown to St. Thomas, U.S. Virgin Islands, where they boarded the ship to investigate the illness outbreak. By January 29, 2014, the Explorer was back in Bayonne, two days earlier than the scheduled return date. As of that date, the CDC reported, over 20 percent of the passengers and more than 4 percent of the crew had become ill with a sickness that has yet to be identified, but is suspected to be Norovirus, an extremely contagious virus that causes acute gastroenteritis (GI). While cruise ship Norovirus and other similar outbreaks have become quite common in the recent years, the onset of infection on the Explorer is the largest documented case of widespread sickness on a cruise ship in two decades.

Norovirus

Norovirus is both the most common cause of acute GI and the most common catalyst for foodborne disease outbreaks in the United States. According to the CDC, each year Norovirus causes 19 to 21 million illnesses, results in hospitalization for 56,000 to 71,000 of its victims, and is even reported to cause death in 570 to 800 cases. Most often, Norovirus causes vomiting, stomach cramping, nausea, and diarrhea. The virus spreads quickly and easily through human contact with those infected and the consumption of infected food and water, as well as contact with infected surfaces and objects. According to CDC data, over 90 percent of diarrheal disease outbreaks on cruise ships are caused by the Norovirus.

Vessel Sanitation Program

The Vessel Sanitation Program (VSP), which is part of the National Center for Environmental Health’s Division of Emergency and Environmental Health Services and which is authorized to operate pursuant to 42 U.S.C. section 264, assists the cruise ship industry in preventing and stopping the spread of GI illnesses on cruise ships. The VSP is carried out through: 1) periodic and unannounced inspections of vessels; 2) monitoring illnesses and investigating outbreaks; 3) providing training for cruise ship employees; and 4) providing health education and current public health information to the cruise industry. Ships must pay annual fees inspection fees based on vessel size as part of the VSP.

CDC Evaluation of the Explorer

The CDC report on the Explorer incident stated that of the 3071 passengers and 1166 crew members aboard, 634 passengers and 54 crew members reported experiencing illness, predominantly in the form of vomiting and diarrhea. In response to the record-breaking outbreak the CDC outlined a six point plan of action for the Explorer during the affected itinerary which included: 1) increased cleaning and disinfection procedures; 2) communicating the existence of the outbreak with passengers through announcements that encourage case reporting; 3) the collection of stool samples from infected passengers and crew, which were submitted to the CDC lab; 4) the execution of multiple, daily reports to the VSP; 5) adding crew members during the ten-day voyage to assist with the execution of the CDC plan; and 6) consultation with the CDC in regard to the next scheduled itinerary of the Explorer, scheduled on January 31, 2014 as well as the disembarkation of infected patients from the ship.

Implications

In addition to the cause of the illness, other questions remain as well. Many have raised issues regarding the reliability of the official number of sick passengers, as some claim the number was even higher than the CDC data suggests. Accounts of the cruise reported by CNN quoted passengers who believed that many of the sick travelers did not bother to report their illness, while others would not admit they were infected for fear of being quarantined to their cabins. Further, because Norovirus lives in the system for several days after an individual has recovered, passengers raised concerns about spreading it beyond the confines of the ship after disembarkation. The CDC recommends the practice of proper hygiene, refraining from preparing food during illness, and the disinfection of contaminated surfaces to prevent the spread of Norovirus.