Background

In 2004, 10.8 million people took North American cruise vacations, and cruising is expected to continue to gain popularity, with an estimated 20.7 million cruise travelers in 2010 (1). Since 1980, the North American cruise industry, which makes up the majority of the global cruise market, has experienced an average annual passenger growth rate of 8.1%. Cruise capacity also increased by 450% over the same period, with 225,714 beds available in 2004. U.S. ports handle about 75% of global embarkations, and 77% of the passengers are U.S. residents (2). The North American cruise industry has had overall passenger occupancies at full capacity in recent years, with top destinations being the Caribbean, the Mediterranean, Alaska, Europe, and the west coast of Mexico. Cruise itineraries are ever expanding to include continents and areas not easily accessible by other means of travel, permitting travelers to visit multiple global destinations in the comfort typically offered by cruise ships (1).

Cruise ships and all ocean-going vessels engaged in international commerce fly flags of registry, which are required for operation in international waters (3). Cruise lines often choose to register either in their country of ownership or ship production or in countries that provide open maritime registration, or “Flags of Convenience.” Ships are most often registered in the United Kingdom, Liberia, Panama, Norway, the Netherlands, the Bahamas, and the United States. Flag registry states provide comprehensive maritime expertise and administrative services, require annual safety inspections before issuance of a passenger vessel certificate, and monitor vessel compliance with international maritime laws, as well as flag state standards. The World Health Organization’s International Health Regulations stipulate health and sanitation requirements for international conveyances. In the United States, the U.S. Coast Guard enforces maritime safety requirements, and CDC has regulatory responsibilities for sanitation and public health on cruise ships bound for a U.S. port from a foreign port (3).

Today’s large cruise ships can serve as a gathering place for the global community, where passengers and crew from around the world bring together a diversity of cultures, as well as medical and immunization backgrounds and health risk behaviors (4,5). Cruise voyages can last from several hours (e.g., gambling cruises) to several months (e.g., around-the-world and semester-at-sea cruises); however, the average duration of cruise travel is about 7 days (1). This time period permits ample opportunity for passengers and crew to come into repeated and prolonged contact through shared activities, such as games and dining, and through resources such as food and water, resulting in opportunities for exposure and transmission of communicable diseases (4,5). In addition, as cruise ships make multiple port stops, where differences may exist in sanitation standards and disease exposure risks, embarking passengers and crew can import and spread communicable diseases onboard. Detecting and preventing infectious diseases acquired during cruises are important not only to protect the health of cruise travelers but to avoid global dissemination of diseases in home communities through disembarking passengers and crew members (5).

CDC's Vessel Sanitation Program (VSP) and Quarantine Stations

In 1975, in response to several large gastrointestinal disease outbreaks on cruise ships, CDC established the VSP, a joint cooperative program with the cruise industry, to achieve a high level of sanitation and minimize the risk of gastrointestinal (GI) disease on cruise ships (6). The VSP encourages the cruise industry to establish and maintain a comprehensive sanitation program, including surveillance for acute gastroenteritis (AGE). The VSP staff conducts biannual, unannounced sanitation inspections on U.S.-bound cruise ships with international itineraries carrying 13 or more passengers. The VSP also engages in the design and construction of new ships, as well as retrofitting older ones to enhance facilities and provisions that promote shipboard sanitation and public health (6).

The VSP shipboard sanitation inspections cover the following areas of public health interest: 1) water supply storage, distribution, disinfection and protection; 2) spas and pools disinfection and filtration; 3) food handling, including storage, preparation, and service; 4) potential for contamination of food, water and ice; 5) personal hygiene and sanitation practices of crew; 6) general cleanliness and condition of the ship, and 7) ship training programs in environmental and public health practices. An inspection score of 86 or higher (out of 100) indicates an acceptable level of sanitation. In general, the higher the score, the higher the level of sanitation, but this score does not reflect the risk of acquiring gastrointestinal disease. The VSP could recommend or require that a cruise ship not sail if sanitation deficiencies could pose a public health threat. The VSP posts most recent sanitation scores and reports for specific cruise ships on its website: http://www.cdc.gov/nceh/vsp (6).

U.S. Federal Quarantine Regulations require that, 24 hours before arrival at a U.S port, vessels notify public health authorities of onboard incidents of death, diarrhea (defined as at least 3 stools in a 24-hour period), and certain febrile syndromes of public health significance (6,7). The VSP receives reports of AGE and may respond with an epidemiologic and environmental investigation if at least 3% of passengers and/or crew members seek medical attention for AGE, or if an unusual GI illness occurs (6). Surveillance and response for reports of onboard deaths and febrile syndromes of public health concern are conducted by CDC Quarantine Stations, located at major U.S. ports of entry and land border crossings and administered by the Division of Global Migration and Quarantine in Atlanta (7).

Cruise Ship Medical Facilities

In 2000, the Cruise Ship and Maritime Medicine Section of the American College of Emergency Physicians (ACEP) published ACEP Health Care Guidelines on Cruise Ship Medical Facilities, a consensus report on appropriate facilities and staffing able to provide basic medical and emergency services aboard cruise ships, within the recognized limitations of the offshore environment (8). These guidelines include provisions for medical facility design on cruise ships, including guidelines for an isolation room to manage communicable diseases, diagnostic and emergency medical equipment, formulary, staff number and qualifications, and a health, hygiene and safety program for medical personnel (8). Large cruise lines that operate in the United States or are members of the International Council for Cruise Lines (ICCL) meet or exceed the ACEP guideline standards. Medical facilities on ICCL member vessels can be equated to community urgent care centers, with the ability to perform basic diagnostics such as blood chemistries, complete blood counts, urinalyses, chest x-rays, and EKGs (3,9). An estimated 95% of illnesses seen in cruise ship medical facilities can be treated onboard; however, passengers with serious problems such as myocardial infarction or cerebrovascular accidents need to be transferred to shoreside hospitals after stabilization (10). Cruise travelers should note that ACEP guidelines for large cruise lines may not be followed by smaller ships or those run by independent operators; on such ships there may be no medical provisions onboard. Cruise ship travelers with chronic diseases or those who may require comprehensive medical care during travel should consult with their health-care providers and notify the cruise line of special needs before travel (9).

Transmission of Illness on Cruise Ships

Heightened disease surveillance efforts by cruise lines in cooperation with public health authorities and awareness among cruise ship travelers have led to the detection of illnesses of potential public health significance that might otherwise have gone unnoticed. Communicable diseases occurring onboard cruise ships reflect similar onshore events, but transmission risk may be enhanced by the crowded, semi-enclosed cruise ship environment, with increased opportunities for interpersonal interactions (4,5,11). In addition, an estimated one-third of cruise travelers are senior citizens who, along with travelers with underlying chronic health problems, are at increased risk of morbidity from infectious agents such as Influenza viruses and Legionella (11-13). A study of cruise ship medical logs showed that over half of infirmary visits are made by passengers over the age of 65; the most common diagnosis is respiratory tract infection, followed by injuries, nervous system (e.g., seasickness) (see Chapter 6) and GI illness (10). In recent years, outbreaks of norovirus and influenza (see Chapter 4) have posed particular public health challenges (11-15). Outbreaks of influenza A and influenza B can occur among cruise ship passengers and crew year-round worldwide. Previous outbreaks have resulted due to importation of influenza from a community in which it was circulating, with subsequent sustained person-to-person spread on cruise ships (11,12). The low infective dose of norovirus, combined with its easy person-to-person transmissibility and ability to survive routine cleaning procedures, has led to large, consecutive cruise outbreaks (14). Other causes of GI illness clusters on cruise ships have included contaminated food or water due to Salmonella spp., enterotoxigenic Escherichia coli, Shigella spp., Vibrio spp., Staphylococcus aureus, Clostridium perfringens, Cyclospora sp., and Trichinella spiralis (5). The estimated likelihood of contracting gastroenteritis on an average 7-day cruise is less than 1%, and GI illness accounts for fewer than 10% of passenger infirmary visits (15).

Legionnaires’ disease has led to pneumonia outbreaks on multiple, consecutive cruises. Passengers typically develop symptoms only upon completion of travel, resulting in delayed detection and continuous transmission (13). Additionally, since cruise travel typically involves stays in hotels as well as multiple environmental exposures during port stops, it is usually difficult to link a cruise ship with infection; however, contamination of ships’ whirlpool spas and potable water supply systems have most commonly been implicated sources (5,13). Clusters of rubella and varicella have been investigated on cruises originating in the U.S. and have highlighted the potential of global dissemination of vaccine-preventable diseases through cruise travel. During one investigation, 11% of the crew was shown to be infected with or susceptible to rubella, and 33% of passengers onboard were women of childbearing age, a high-risk group for congenital rubella syndrome if infected during pregnancy (5). Isolated cases of measles, hepatitis A, typhoid, tuberculosis, meningococcal meningitis have been reported and investigated (unpublished data, CDC Miami Quarantine Station).

Travelers who suspect that they have become ill with a communicable disease during cruise travel should contact the VSP (for GI illness); for other illnesses contact the nearest CDC Quarantine Stations http://www.cdc.gov/ncidod/dq/quarantine_stations.htm or call CDC/DGMQ at 866-694-4867 (6,7).

Injury and Other Health Considerations for Cruise Ship Travel

Injuries are one of the most common reasons for passengers to seek medical care on cruise ships, accounting for about 18% of passenger infirmary visits (10). As a result of climatic variations, environmental exposure to pollutants, changes in diet and physical activity levels and an increased level of stress due to being in an unfamiliar environment, the cruise ship traveler may be subject to exacerbation of existing chronic health conditions (9). A prospective cruise ship traveler with health conditions that might increase his or her potential for injury or illness should consult his or her health-care provider before embarking on a cruise (see Chapter 9). Special cruises are now available for travelers who have certain medical conditions, including those on dialysis (9).

Preventive Health for Cruise Ship Travelers

Due to multiple port visits and potential exposures, cruise ship travelers may be uncertain about which prevention medications, immunizations and behaviors are appropriate for them and for their itineraries (16). In general, travelers should inform the cruise line of special medical needs, such as wheelchair access, oxygen tank, dialysis, etc, in advance of travel (9). Adequate medical insurance coverage for receiving health care overseas and medical evacuation should be ensured (9). Four to six weeks before travel, cruise travelers should consult a health-care provider who can give guidance on appropriate chemoprophylaxis, immunizations, and health behaviors based on a complete review of the health status of the traveler, duration of travel, countries to be visited, and shoreside activities (16,17). Clinicians should provide travelers with 1) destination-specific recommended and required vaccines (e.g., yellow fever), as well as prevention medication (e.g. malaria chemoprophylaxis) if needed; 2) routinely recommended age- and medical condition-specific immunizations, such as MMR and influenza vaccines, if not up to-date; 3) appropriate options for motion sickness based on the individual’s medical history and current medications (see Chapter 6) and 4) a written summary of their medical history, including pertinent diagnostic data such as EKG and chest x-ray, to facilitate overseas medical care, should it be required (9,16,17). Among cruise ship passengers and crew members, risk of exposure to infectious diseases is difficult to quantify because of the broad spectrum of cruise ship experiences and limited data. Travelers should be given guidance on good health habits and disease prevention practices during travel including adequate 1) hand hygiene (i.e., washing hands for at least 20 seconds with soap and water) (http://www.cdc.gov/nceh/vsp/pub/CruisingTips/cruisingtips.htm) or if soap and water are unavailable, using an alcohol-based product containing more than 60% alcohol (18) 2) respiratory hygiene such as using tissue to cover coughs and sneezes (http://www.cdc.gov/flu/protect/covercough.htm); 3) food and water intake precautions (i.e., eating foods that are thoroughly cooked and of appropriate temperate) (see Chapter 2); and 4) mosquito prevention (i.e., using DEET-containing repellents, bed nets, and clothing that provides more coverage over exposed areas of the body (see Chapter 2) (17). Health-care providers can contribute to healthy environments on cruise ships by questioning ill returned travelers (see Chapter 2) about recent cruise vacations and promptly reporting any suspected communicable disease to public health authorities (16).

References

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2. The Cruise Industry 2004 Economic Summary [internet]. Arlington (Virginia): International Council of Cruise Lines (US); [date unknown]-[cited 20 June 2006]. Available from: http://www.iccl.org/resources/economicstudies.cfm.
3. Cruise Industry FAQ [internet]. Arlington (Virginia): International Council of Cruise Lines (US); [date unknown]-[cited 20 June 2006]. Available from http://www.iccl.org/faq/imi.cfm.
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KIREN MITRUKA