ARCHIVED - Statement on Cruise Ship Travel

Canada Communicable Disease Report
Volume 31 • ACS-8
15 October 2005

An Advisory Committee Statement (ACS)

Committee to Advise on Tropical Medicine and Travel (CATMAT)*?

PDF Version
24 Pages - 348 KB

Preamble

The Committee to Advise on Tropical Medicine and Travel (CATMAT) provides the Public Health Agency of Canada (PHAC) with ongoing and timely medical, scientific, and public health advice relating to tropical infectious disease and health risks associated with international travel. PHAC acknowledges that the advice and recommendations set out in this statement are based upon the best current available scientific knowledge and medical practices, and is disseminating this document for information purposes to both travellers and the medical community caring for travellers.

Persons administering or using drugs, vaccines, or other products should also be aware of the contents of the product monograph(s) or other similarly approved standards or instructions for use. Recommendations for use and other information set out herein may differ from that set out in the product monograph(s) or other similarly approved standards or instructions for use by the licensed manufacturer(s). Manufacturers have sought approval and provided evidence as to the safety and efficacy of their products only when used in accordance with the product monographs or other similarly approved standards or instructions for use.

Introduction

Cruises pose a potentially important public health challenge. Their popularity has increased tremendously in the past 10 years. Cruise passenger traffic in Canada tripled from 221,000 arrivals in 1990 to 636,000 in 2000. In 2003, Statistics Canada reported that there were 728,000 international cruise arrivals to the east and west coasts of Canada with 563,000 arrivals in the west and 165,000 arrivals in the east. Worldwide, the number of passengers increased from fewer than 1. 5 million in 1980 to almost 6. 9 million in 2000^(1,2).

The size of individual cruise ships is also steadily increasing, many carrying up to 3,000 passengers and 1,500 crew members⁽³⁾. Time lines between cruises are typically tight, leaving little room for public health interventions. Most cruises last 7 to 10 days, at the end of which the ship docks in port, unloads its passengers, is cleaned and restocked, and receives a new complement of passengers, all in a single day.

Passengers tend to originate from affluent countries with low rates of diseases such as hepatitis A and tuberculosis. While some cruises attract primarily an elderly population in various states of health, many cruises have become popular with middle-aged and young adults, and passengers now often include children and pregnant women. Passengers on so-called "singles" cruises may incur particular risk for acquisition of sexually transmitted diseases (STDs). Because many crew members come from the developing world, they are at greater risk of harboring infections such as tuberculosis and hepatitis B, and have greater likelihood of susceptibility to diseases such as rubella.

Epidemiology of illness and injury on cruises

No international body regulates the practice of medicine at sea, and the quality of care varies widely⁽⁴⁾. The specific needs of a cruise ship medical service are influenced by variables such as ship size, itinerary, anticipated patient mix, anticipated number of patient visits, etc. Consensus-based guidelines for the practice of medicine on cruise liners exist, but their implementation depends upon each individual cruise line⁽⁵⁾. The guidelines of the American College of Emergency Physicians can be accessed at www.acep.org. In collaboration with the cruise ship industry, Health Canada operates a voluntary compliance inspection program of cruise vessels that visit Canadian ports in order to limit the introduction of communicable diseases into Canada⁽⁶⁾.

Rates of medical problems on board cruise ships have been reported in three recent case series^(4,7,8). The most common diagnosis in passengers was respiratory illness (26% to 29%). Contact dermatitis was more common among crew members⁽⁴⁾. Injuries, most frequently sprains, and superficial wounds and contusions accounted for a significant proportion of ship-board medical visits (10% to 18%)^(7,8). All types of gastrointestinal (GI) illness accounted for 9% to 16% of visits. Although much of the cruise ship medical literature focuses on infectious gastroentteritis, rates among passengers were actually quite low, at
< 3% and 4%, and most cases occurred in persons who had eaten off ship^(4,8). The rate of seasickness (8%) was reported in only one study⁽⁷⁾. From 3% to 11% of shipboard consultations were urgent or emergent, a finding considered significant by all authors. Passengers with conditions requiring air evacuation were more likely to be older (> 59 years)⁽⁹⁾. The rate of medical consultation on cruises was higher than that on shore⁽⁴⁾. Although crew members were usually significantly younger than passengers, they tended to make proportionately more medical visits^(4,8).

Health Canada - Workplace Health and Public Safety
Programme

Health Canada's Cruise Ship Inspection Program (CSIP) was derived from and harmonized with the Vessel Sanitation Program (VSP) of the US-based Centers for Disease Control and Prevention (CDC) in 1998. The CDC developed and implemented the comprehensive VSP following shipboard outbreaks of shigellosis and typhoid in the early 1970s as a cooperative activity with the cruise ship industry^(10,11). Canada's CSIP focuses its activities on vessels with a foreign itinerary that carry 13 or more passengers and call at a Canadian port. The primary activities of the CSIP include comprehensive inspection and consultations with respect to water quality, food safety and environmental sanitation, surveillance of GI illness, and outbreak investigations on vessels⁽¹²⁾.

On a volunteer basis, cruise ships maintain GI surveillance data and make the information available for review by CSIP during inspections and outbreak investigations. Vessels must submit routine GI disease surveillance reports to CSIP between 24 and 30 hours before the expected arrival at a Canadian port. A reportable case of illness on a cruise ship is defined as (a) three or more episodes of loose stools in a 24-hour period, or (b) vomiting and one additional symptom (one or more episodes of loose stools in a 24-hour period or abdominal cramps, headache, muscle aches or fever) that has been reported to designated staff by a passenger or crew member. Nausea is excluded from the GI illness case definition in order to prevent the inclusion of cases of seasickness. Reportable GI cases also apply to crew members with onset of symptoms up to 3 days before boarding the vessel⁽⁶⁾.

Vessels must submit an immediate report to CSIP at any time during a cruise (including travel between two Canadian ports) when the cumulative percentage of GI cases reaches 2% among passengers or 2% among crew, and the vessel is within 15 days of expected arrival at a Canadian port. CSIP may conduct further investigations and/or implement control measures, depending on the number of affected passengers or crew and the severity and type of illness observed. Because some cruises routinely alternate between Canadian and US ports (e. g. Vancouver and Alaska), CSIP may request the involvement of the CDC's VSP in outbreak investigations⁽⁶⁾.

CSIP also performs unannounced inspections of all cruise ships at least once a year. Sanitation scores are assigned (passing score > 85%), and these are published on the CSIP Website at http://www.hc-sc.gc.ca/hl-vs/travel-voyage/general/inspection/cruise_ship-navires_croissieres_e.html. The VSP inspection scores can be accessed on the CDC Website at www.cdc.gov/nceh/vsp/default.htm.

The VSP has been evaluated in descriptive epidemiological studies during five periods from 1975 to 2000⁽¹³⁾. The success of the program in reducing the frequency of diarrheal disease outbreaks is illustrated in Table 1. In collaboration with the cruise ship industry, the VSP improved sanitary engineering and operational procedures aboard cruise ships, resulting in a significant increase in median ship sanitation scores over the past decade. When the VSP began, none of the ships passed inspection. By 1978, 50% had achieved passing scores⁽¹¹⁾. These improvements have resulted in a marked reduction in outbreak frequency to 3. 7 per 1,000 cruises in 2003⁽¹⁴⁾. Foods most commonly implicated in outbreaks were seafood, eggs, potato and chicken salads, and ice cream or creamy desserts. On-board outbreaks due to seafood and eggs were reduced by one-third between 1986 and 1993 with thorough cooking of shellfish and use of pasteurized eggs⁽¹⁰⁾.

Specific risks

1. Food and water-borne illness

A. Infectious diarrhea

Although travellers' diarrhea afflicts 20% to 50% of land-based travellers to developing countries, the incidence is generally much lower on cruises, while still higher than that of the nontravelling US population^(4,7,8,11). Like other travellers, cruise passengers do not always choose to seek medical care, and this results in undetected cases. Merson et al. found that the incidence of diarrhea, as reported by questionnaire, was at least four times higher than that recorded in the medical logs⁽¹¹⁾.

Outbreaks of GI disease on cruise ships over the last decade have been linked to noroviruses, enterotoxigenic Escherichia coli or "unknown" causes⁽¹⁴⁾. A list of diarrheal outbreaks reported on cruise ships since 1994 is available on the VSP website at http://www. cdc. gov/nceh/vsp/surv/gllist. htm.

While there has been an overall decrease in the incidence of infectious diarrhea on cruise ships, frequent outbreaks caused by food and water contamination on ship continue, and there has been a recent 13% to 29% increase in the proportion of gastroenteritis cases caused by the Norovirus , commonly called the Norwalk virus^(15-21). The Norovirus is very hardy, capable of surviving on practically all surfaces, including door handles, sinks, railings and glassware. The closed living environment aboard a ship and the possibility of aerosol transmission can significantly increase the risk of viral gastroenteritis⁽²²⁾. When the environmental contamination is too great on a cruise ship, both the CSIP and VSP can request that the ship be removed from service to break the cycle.

Bacteria account for about 39% of cases, with enterotoxigenic E. coli (ETEC) as the leading cause⁽⁴⁾. Three recent outbreaks of ETEC were associated with consumption of ice on board ship⁽²³⁾.

The source of a fourth outbreak, reported in 2002, is not available⁽²⁴⁾. Shigella and Salmonella outbreaks have also been reported^(24,25).

Passengers should be advised to practise good personal hygiene
(e. g. hand washing), especially after using the bathroom and before handling food, as hand washing is the single most important procedure for preventing infections⁽²⁶⁾. As well, passengers, especially those who intend to eat off-ship or who take cruises originating in developing countries, should follow safe food and water practices, as outlined in the CATMAT Statement on travellers' diarrhea (2001)⁽²⁷⁾.

B. Populations at special risk of infectious diarrhea

The elderly may be at increased risk of viral gastroenteritis because of immunologic changes associated with age (e. g. loss of specific antibodies, decreases in cellular immunity, and chronic diseases). The elderly, children and those with underlying medical conditions might be at increased risk of complications because of volume depletion and electrolyte disturbances. Drugs that reduce gastric acidity (e. g. antacids, H2-blockers, proton pump inhibitors) can markedly increase susceptibility to gastrointestinal pathogens, and diuretics can increase the risk of an adverse outcome in what might otherwise be a mild diarrheal episode⁽²⁷⁾.

Few studies have assessed the role of viral agents causing gastroenteritis in people with HIV/AIDS. People with HIV/AIDS are, however, at increased risk of diarrhea caused by bacteria (e. g. Salmonella , atypical Mycobacteria ) and protozoa, especially Cryptosporidium parvum⁽²⁸⁾. Protease inhibitors, taken by many people with HIV/AIDS, can also cause chronic diarrhea. This drug-induced diarrhea can mimic and mask infectious diarrhea, thereby increasing the potential for transmission to others.

C. Hepatitis A

Hepatitis A is an acute, self-limited viral disease transmitted by the fecal-oral route. Disease may be sporadic or epidemic. It is a potential risk to cruise travellers through contaminated food or water. The incidence of hepatitis A varies widely from country to country and is inversely proportional to the general level of hygiene. Adults from developing countries are often immune, and those from affluent countries are commonly susceptible. Exposure may occur on board ship or on related land-based tours. The long incubation period, 14 to 56 days, usually results in symptoms occurring well after the cruise. The incidence of hepatitis A acquired on board ship is unknown, but it is presumed to be low. The entire trip, cruise and land, must be assessed as a whole to ascertain hepatitis A risk.

A single dose of hepatitis A vaccine provides up to 1 year's protection, and a booster dose provides immunity for at least 10 to 20 years. Several killed inactivated hepatitis A vaccines are licensed in Canada. They are all safe and effective and are considered to be interchangeable⁽²⁹⁾. Indications for vaccination should be assessed individually as for any other trip or contact.

2. Respiratory infections, rubella and tuberculosis

Aspects of the cruise ship environment that lend themselves to the spread of serious respiratory and airborne infections include the following:

• the demographic characteristics of passengers and crew, including susceptible elderly passengers from multiple places of origin;
• common ventilation system for a large population; and
• special facilities such as spas, pools and buffet-misting devices that generate aerosols.

A. Influenza and influenza-like illness (ILI)

Since 1997, there have been seven reports of influenza outbreaks on board cruise ships in the northern hemisphere. Most have been due to influenza A and have occurred during the summer or early autumn, before any annual influenza program implemented in the northern hemisphere; people who were vaccinated in the previous ?flu season may not have had sufficient protection. Several have represented the first introductions of southern hemisphere strains to the northern hemisphere(30,31). In 2002, Australia reported a large outbreak of influenza A and B on a cruise ship travelling between Sydney, Australia, and Noumea, New Caledonia. This outbreak coincided with the peak influenza period in Sydney(32).

Crew members have, on occasion, been reservoirs of infection, effectively bridging viruses from cruise to cruise on the same ship. Control measures - cohorting of sick individuals, vaccination, and anti-viral prophylaxis - have had mixed results^(33-36).

Predeparture influenza immunization for prevention of the disease in high-risk travellers should be considered. There is insufficient evidence at this time to advise in favour of, or against, routine reimmunization of travellers or crews who were immunized in the fall and who are subsequently travelling to regions where influenza may be circulating in the late spring and summer months⁽³⁷⁾. A study in which individuals were given a second dose of influenza vaccine 12 weeks after the first dose suggests that revaccination is ineffective⁽³⁸⁾.

Amantadine, which is protective against influenza A, and oseltamivir, which is protective against both influenza A and B, are approved in Canada for the prophylaxis of influenza in certain settings. Recommendations for the appropriate use of these products can be found in the National Advisory Committee on Immunization (NACI) Statement on influenza vaccination published each year in the CCDR⁽³⁹⁾. Cruise ship travellers at high risk should consider carrying a supply of amantadine or oseltamivir for postexposure prophylaxis in the event of an influenza outbreak during their cruise⁽³⁷⁾.

Pneumococcal vaccine reduces the incidence of bacteremic pneumococcal pneumonia in susceptible populations. Vaccination with either the 7-valent, conjugated vaccine or the 23-valent, polysaccharide vaccine (or both) is routinely recommended for those at high risk of invasive pneumococcal disease. The planning of a cruise can be an excellent opportunity to ensure appropriate pneumococcal vaccination of the elderly (> 60 to 65 years of age depending on the province/territory). It may also reduce the frequency of complications of influenza and lower respiratory tract infections resembling influenza⁽⁴⁰⁾.

B. Legionella

Over 100 cases of legionnaires' disease have been linked to ships, most cases occurring on cruise ships. Ten patients are known to have died. Most of the cases have been reported in travellers> 50 years of age. Several sources for these infections have been identified, including spas, air handling units, and potable water⁽⁴¹⁾.

The last ship outbreak of Legionella reported in the Americas was in 1994. Improvements in vessel construction standards and recently imposed controls on potable water, air quality, and spas and pools should reduce the risk of legionnaires' disease⁽⁴²⁾. Although no vaccine is available, antibiotic treatment is usually effective⁽⁴³⁾.

Legionella must be considered in the differential diagnosis of acute febrile illness, bronchitis or pneumonia in someone currently taking, or who has recently completed, a cruise.

C. Rubella

To date, outbreaks of rubella have been limited to crew members on cruise ships. In 1997, two clusters of rubella infections were reported on commercial cruise ships. In one outbreak, 16 of 385 crew (4%) aboard ship were infected; half were asymptomatic. Seven percent of the crew were found to be susceptible but remained uninfected. No passengers were infected in either outbreak(44).

Many crew members of cruise ships are from countries without routine rubella vaccination programs. Because of the risk of congenital rubella syndrome, women of childbearing age - especially those who are currently, or wish to become, pregnant - should be assessed for their rubella immunity status before they travel on cruise ships and offered rubella-containing vaccine (MMR), if not pregnant⁽⁴⁴⁾.

D. Tuberculosis

Although the demographic features of cruise ships suggests a risk of tuberculosis spread among crew and passengers, no such spread has been documented to date. Experience from airline travel suggests limited transmission of tuberculosis in public transportation settings and then only to close contacts⁽⁴⁵⁾.

E. Severe acute respiratory syndrome (SARS)

Although there have been no reported cases of SARS associated with cruise travel, cruise ships bring together large numbers of people from afar and thus could serve to amplify the spread of a communicable disease such as SARS. Other respiratory infections, such as influenza and legionnaires' disease, have certainly been issues on cruises.

Information regarding the approach to the management of SARS on cruise ships can be accessed through the Public Health Agency of Canada at www. phac-aspc. gc. ca.

3. Mosquito-borne diseases

A. Malaria

Malaria is a mosquito-borne, protozoan disease that is widespread in tropical and subtropical countries. Malaria is transmitted by Anopheles mosquitoes, which generally bite between dusk and dawn. The practice of ocean-going cruise ships to sail at night and be in port during the day lessens the passengers' exposure to land-based mosquitoes. The risk of malaria on ocean cruises in tropical African waters and the Indian subcontinent is uncertain but is likely to be significant. There is minimal risk on cruises visiting urban centres elsewhere in Asia. Some risk probably exists on cruises along the west coast of South America (Ecuador and Peru north of Lima). Except for Haiti and the Dominican Republic, there is no known risk of malaria on Caribbean cruises^(46,47).

There is risk of malaria on Amazon cruises and those on African rivers in malaria-endemic areas. Antimalarial prophylaxis is not recommended for cruises on the Yangtze River in China, nor is there a risk on Nile River cruises^(46,47).

B. Dengue fever

Dengue fever is a cosmopolitan, viral illness transmitted by day-biting mosquitoes. It is widespread in tropical and subtropical climates. There are no data on cruise-associated infection. Protection involves on-board mosquito control and, at an individual level, personal protective measures. Travellers should be advised to use personal protective measures on land-based tours should the local disease situation warrant it⁽⁴⁸⁾.

C. Yellow fever

Yellow fever is a mosquito-borne viral illness, endemic in tropical South America and Africa. There is no risk in Asia, on Caribbean cruises or in the Panama Canal Zone, but risk exists on Amazon cruises, on river cruises in endemic areas in Africa, and in some urban areas in endemic zones of Africa and South America.

Yellow fever vaccination is the only immunization that may be demanded by a country under the World Health Organization's International Health Regulations. Yellow fever vaccination must be considered in both medical and regulatory contexts.

Yellow fever vaccine, the mainstay of prevention against the disease, is a live virus vaccine. Revaccination is recommended every 10 years, though there may be lifelong protection after a single dose. The vaccine is absolutely or relatively contraindicated in infants < 9 months, in persons with known anaphylaxis to hens' eggs, pregnant women and in the immunocompromised⁽⁴⁹⁾. Since 1996, 23 global cases of viscerotropic disease associated with yellow fever vaccine have been reported, with 14 fatalities. Risk appears to be highest in persons> 65 years of age and in persons with thymus dysfunction^(49-52). No cases have occurred in Canada⁽⁵³⁾.

National policies regarding yellow fever vaccine may require vaccination of all incoming travellers or only of those coming from an endemic or infected area. For example, in theory, cruise travellers stopping in certain Caribbean countries after prior visits to northern South America would require yellow fever vaccine.

Anecdotal evidence suggests that there is inconsistency of enforcement of these regulations.

D. STDs

The rate of casual sex (i. e. sex with a previously unknown partner) during short-term travel is at least 5% to 9%^(54-56) ,and travel-acquired STDs are common^(57,58). No studies specific to cruise travel and STDs were found.

Objectively identifiable risk factors for travellers in general include male sex, single status, solo travel and a history of casual sex^(55,56,58). In a recent Canadian study, 40% of travellers who had had casual sex abroad had planned to do so before departure, and only 69% used condoms⁽⁵⁴⁾. Young women are more likely to have casual sex with fellow travellers than with locals, but they are less likely to use condoms⁽⁵⁵⁾.

Studies have reported that knowledge about the risk of HIV and AIDS had no significant effect on risk behaviour during travel^(55,56). Counseling regarding prevention of STDs, including HIV, offers travellers the opportunity of informed choice and may set the stage for more effective interventions.

The only vaccine-preventable STD is hepatitis B. Pretravel planning provides a good opportunity for health professionals to offer hepatitis B vaccination to those who wish to be protected⁽⁴⁹⁾.

4. Non-infectious illness

A. Seasickness

Naus , the ancient Greek word for ship, has given rise to the modern term "nausea". Long the bane of seafarers, motion sickness is most intense when acceleration is in a direction perpendicular to the body and is most frequent with up and down motion (e.g. riding a swell). Incidence peaks among those between 3 and 12 years of age and is 1.7 times higher in females than in males⁽⁵⁹⁾.

Although popular belief and cruise ship brochures favour the theory that central cabin location reduces seasickness, studies have not consistently supported this claim. A recent study reported no association between motion sickness and cabin location on a very rough Antarctic voyage⁽⁶⁰⁾.

Motion sickness can be reduced in many people by preventive antinauseants. Those recommended are summarized in Table 2.

While many of the agents are not recommended in children < 2 years, it is rare for children of this age to experience motion sickness⁽⁵⁹⁾. The scopolamine patch is contraindicated in persons with glaucoma and should be avoided in the young, the elderly, during pregnancy, and when there is urinary or pyloric obstruction⁽⁵⁹⁾. Alcohol can intensify the side effects of all these medications. No antiemetic has been shown to be entirely safe during pregnancy⁽⁶¹⁾. Preventive antiemetics should only be used in pregnancy in consultation with an expert on the use of drugs in pregnancy.

B. Mal de debarquement syndrome (MDD)

Mal de debarquement syndrome (MDD) or disembarkation sickness is a relatively rare syndrome that usually follows a sea voyage but can also occur after extended train travel or motion in a slowly revolving room. Symptoms, which occur only after the voyage, include sensations of rocking and swaying and, usually, imbalance. They can persist for a month and up to several years (mean 3.5 years). By contrast, land-sickness (postmotion vertigo) typically lasts < 48 hours⁽⁶²⁾.

MDD usually affects women between 40 and 50 years of age. The cause is uncertain. Symptoms do not respond to treatment with medication active against seasickness or dizziness. Benzodiazepines seem to be the most useful treatment, perhaps because of their vestibular suppressant action. No methods of prevention are known⁽²⁾.

Recommendations

Table 3 presents evidence-based medicine categories for the strength and quality of the evidence for the recommendations that follow (refer to Tables 4 and 5).

References

1. McDougall L. Canada benefiting from cruising boom. Statistics Canada. Travel-log 2001;20:2.

2. International travel survey Ottawa: Statistics Canada, 8 September, 2004.

3. Hill CD. Capabilities and limitations of cruise ship physicians. Abstract. Symposium S6.3: Cruise Ship Health: 6^th Conference of the International Society of Travel Medicine 1999, June 6-10, Montreal, Canada.

4. Dahl E. Anatomyofaworldcruise. J Travel Med 1999;6:168-71.

5. American College of Emergency Physicians. Health care guidelines for cruise ship medical facilities. Reaffirmed Oct. 2001. (www.acep.org). Accessed from internet August 21, 2005.

6. Health Canada. Cruise ship inspection program administrative guide. Workplace Health and Public Safety Programme, Public Health Bureau. Ottawa: Health Canada, April 2004.

7. DiGiovanna T, Rosen T, Forsett R et al. Shipboard medicine: a new niche for emergency medicine. Ann Emerg Med 1992;21:12.

8. Peake DE, Gray CL, Ludwig MR et al. Descriptive epidemiology of injury and illness among cruise ship passengers.AnnEmerg Med 1999;33:1.

9. Prina DL, Orazi UN, Weber E. Evaluation of emergency air evacuation of critically ill patients from cruise ships. J Travel Med 2001;8:285-91.

10. Koo D, Maloney K, Tauxe R. Epidemiology of diarrheal disease outbreaks on cruise ships, 1986 through 1993. JAMA 1996;275(7):545-47.

11. Addiss DG, Yashuk JC, Clapp DE et al. Outbreaks of diarrhoeal illness on passenger cruise ships, 1975-85. Epidemiol Infect 1989;103:63-72.

12. Health Canada. Workplace Health Public Safety Program annual report: gastrointestinal illness surveillance system for cruise ships. Ottawa: Health Canada, 2001.

13. Cramer EH, Gu DX, Durbin RE, & Vessel Sanitation Program Environmental Health Inspection Team. Diarrheal disease on cruise ships, 1990/2000: the impact of environmental health programs. Am J Prev Med 2003;24(3):227-33.

14. Lawrence DN. Outbreaks of gastrointestinal diseases on cruise ships: lessons from three decades of progress. Curr Infect Dis Rep 2004;6:115-23.

15. Kim DK, Harper DA, Hill TA et al. Trends in outbreaks of gastroenteritis on board passenger vessels: a public health threat by small round-structured viruses. Abstract. Symposium S6.1: Cruise Ship Health: 6th Conference of the International Society of Travel Medicine 1999. June 6-10, Montreal, Canada.

16. Gunn RA, Terranova WA, Greenberg HB et al. Norwalk virus gastroenteritis aboard a cruise ship: an outbreak on five consecutive cruises. Am J Epidemiol 1980;112(6):820-27.

17. Centers for Disease Control and Prevention. Gastroenteritis outbreaks on two Caribbean cruise ships. MMWR 1986;35(23):383-84.

18. Ho M-S, Glass RI, Monroe SS et al. Viral gastroenteritis aboard a cruise ship. Lancet 1989;(Oct 21):961-65.

19. Herwaldt BL, Lew JF, Moe CL et al. Characterization of a variant strain of Norwalk virus from a food-borne outbreak of gastroenteritis on a cruise ship from Hawaii. J Clin Microbiol 1994;32(4):861-66.

20. McEvoy M, Blake W, Brown D et al. An outbreak of viral gastroenteritis on a cruise ship. Commun Dis Rep 1996;6:R188-92.

21. Centers for Disease Control and Prevention. Outbreaks of gastroenteritis associated with noroviruses on cruise ships: United States, 2002. MMWR 2002;51(49):1112-15.

22. Centers for Disease Control and Prevention. Viral agents of gastroenteritis: public health importance and outbreak management. MMWR 1990;399:RR50:1-24.

23. Daniels NA, Neimann J, Parashar UD et al. Traveler's diarrhea at sea: three outbreaks of waterborne enterotoxigenic Escherichia coli on cruise ships. J Infect Dis 2000;181(4):1491-95.

24. Centers for Disease Control and Prevention. Cruise ship outbreaks by year. http://www.cdc.gov/nceh/vsp/surv/ outbreakslist.pdf

25. Centers for Disease Control and Prevention. Outbreak of Shigella flexneri 2a infections on a cruise ship. MMWR 1994;43(35):657.

26. Health Canada. Infection control guidelines. Hand washing, cleaning, disinfection and sterilization in health care. CCDR 1998;24(S8).

27. Committee to Advise on Tropical Medicine and Travel (CATMAT). S tatement on travellers' diarrhea. CCDR 2001;27(ACS-3):1-12.

28. Committee to Advise on Tropical Medicine and Travel (CATMAT). Statement on travellers and HIV/AIDS. CCDR 1994;20(17):147-49.

29. Committee to Advise on Tropical Medicine and Travel (CATMAT). Statement on hepatitis A vaccines for travellers. CCDR 2001;27(ACS-2):3-11.

30. Uyeki TM, Zane SB, Bodnar UR et al. Large summertime influenza A outbreak among tourists in Alaska and the Yukon Territory. Clin Infect Dis 2003;36:1095-1102.

31. Health Canada. Influenza in travelers to Alaska, the Yukon Territory, and west coast cruise ships, summer of 1999. CCDR 1999; 25(16):137-41.

32. Brotherton JM, Delpech VC, Gilbert GL et al. & Cruise Ship Outbreak Investigation Team. A large outbreak of influenza A and B on a cruise ship causing widespread morbidity. Epidemiol Infect 2003;130(2):263-71.

33. Centers for Disease Control and Prevention. Outbreak of influenza-like illness in a tour group - Alaska. MMWR 1987;36(42):697-99,704.

34. Centers for Disease Control and Prevention. Acute respiratory illness among cruise ship passengers: Asia. MMWR 1988;37:63-6.

35. Miller JM, Tam TW, Maloney S et al. Cruise ships: high-risk passengers and the global spread of new influenza viruses. Clin Infect Dis 2000;31:433-38.

36. Centers for Disease Control and Prevention. Influenza B virus outbreak on a cruise ship: Northern Europe, 2000. MMWR 2001;50(8):137-40.

37. Committee to Advise on Tropical Medicine and Travel (CATMAT). Statement on travel, influenza and prevention. CCDR 2005;31(ACS-2):1-7.

38. Buxton JA, Skowronski DM, Ng H et al. Influenza revaccination of elderly travelers: antibody response to single influenza vaccination and revaccination at 12 weeks. J Infect Dis 2001;184:188-91.

39. National Advisory Committee on Immunization (NACI). Statement on influenza vaccination for the 2005-2006 season. CCDR 2005;31(ACS-6):1-32.

40. Pneumococcal vaccine: an emerging consensus. Editorial. Ann Intern Med 1988;108(5):757-59.

41. Rowbotham TJ. Legionellosis associated with ships: 1977-1997. Commun Dis Public Health 1998;1(3).

42. Minooee A, Rickman LS. Infectious diseases on cruise ships. Clin Infect Dis 1999;29(4):737-43.

43. Edelstein PH. Antimicrobial chemotherapy for Legionnaire's disease: a review. Clin Infect Dis 1995;21(3):S265-70.

44. Centers for Disease Control and Prevention. Rubella among crew members of commercial cruise ships: Florida, 1997. MMWR 1998;46(52):1247-50.

45. Kenyon TA, Valway SE, Ihle WW et al. Transmission of multidrug-resistant Mycobacterium tuberculosis during a long airplane flight. N Engl J Med 1996;334:933-38.

46. Health Canada. 2004 Canadian recommendations for the prevention and treatment of malaria among international travellers. CCDR 2004;30(S1).

47. Centers for Disease Control and Prevention. Health information for international travel 2001-2002. Atlanta, GA: CDC, US Department of Health and Human Services, 2001.

48. Committee to Advise on Tropical Medicine and Travel (CATMAT). Travel medicine recommendation: dengue fever and international travel. CCDR 1996;22(4):25-28.

49. Health Canada. Canadian immunization guide ,6^th ed. Ottawa: Health Canada, 2002.

50. Martin M, Weld LH, Tsai TF et al. & the GeoSentinel Yellow Fever Working Group. Advanced age as a risk factor for severe adverse events due to yellow fever vaccine. Emerg Infec Dis 2001;7(6).

51. Centers for Disease Control and Prevention. Adverse events associated with 17D-derived yellow fever vaccination: United States, 2001-2002. MMWR 2002;51(44):989-93.

52. Eidex RB. History of thymoma and yellow fever vaccination.Lancet 2004;364(9296):936.

53. Health Canada. Review of adverse events reported following use of yellow fever vaccine: Canada, 1987-2000. CCDR 2002;28(2):9-15.

54. Correia JD, Shafer RS, Patel V et al. Blood and body fluid exposure as a health risk for international travellers. J Travel Med 2001;8:263-66.

55. Gagneux OP, Blöchliger CU, Tanner M et al. Malaria and casual sex: what travelers know and how they behave. J Travel Med 1996;3(1):14-21.

56. Gehring TM, Widmer J, Kleiber D et al. Are preventive HIV interventions at airports effective? J Travel Med 1998;5(4):205-9.

57. Bavastrelli M, Midulla M, Rossi D et al. Sexually active adolescents and young adults: a high risk group for Chlamydia trachomatis infection. J Travel Med 1998;5(2):57-60.

58. Hawkes S, Hart GJ, Bletsoe E et al. Risk behavior and STD acquisition in genitourinary clinic attendees who have travelled. Genitourin Med 1995;71(6):351-54.

59. Committee to Advise on Tropical Medicine and Travel (CATMAT). Statement on motion sickness. CCDR 2003;29(ACS-11):1-12.

60. Gahlinger PM. Cabin location and the likelihood of motion sickness in cruise ship travellers. J Travel Med 2000;7:120-24.

61. Briggs GG, Freeman R, Yaffe JS. Drugs in pregnancy and lactation ,6^th ed. Philadelphia: Lippincott Williams & Wilkins, 2002.

62. Hain TC, Hanna MA, Rheinberger MA. Mal de debarquement. Arch Otolaryngol Head Neck Surg 1999;125:615-20.

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* Members: Dr. B. Ward, Dr. K. Kenneth Gamble, Dr. J. R. Salzman, Dr. P. J. Plourde, Dr. A. McCarthy, Dr. S. Kuhn, Ms. H. Birk, Dr. C. Beallor, Dr. K. L. McClean, Dr. S. Houston

Ex-Officio Members: Dr. J. Given, Dr. P. Kozarsky ,Dr. M. Parise, Dr. P. McDonald, Dr. E. Gadd, Dr. B. Dobie, Dr. M. Tepper, Dr. N. Gibson, Dr. R. Corrin

Member Emeritus: Dr. C. W. L. Jeanes.

Liaison Representatives: Dr. C. Greenaway, Dr. R. J. Birnbaum, Dr. R. Saginur, Dr. P. Teitelbaum, Dr. C. Hui

?This statement was prepared by Dr. R. Saginur and Ms. H. Birk and approved by CATMAT.