Influenza on West Coast Cruise Ships and Land-based Tours in Alaska and the Yukon Territory

Updated: July 26, 1999

Current Situation

Health Canada and provincial/territorial public health authorities are continuing surveillance for reports of influenza and influenza-like illnesses (ILI) on west coast cruise ships and land-based tours in Alaska and the Yukon Territory, and are collaborating on control measures (see Recommendations, below). Most cruise ship operators have also instituted surveillance and influenza prevention and treatment programs.

Reports of respiratory illness continue to be primarily associated with groups of tourists sharing transportation and accommodation on overland tours in the region. After touring inland, some ill travellers are boarding cruise ships contributing to limited spread among other cruise passengers and crew members. No increases in influenza and ILI have been detected in the general populations of Alaska, British Columbia or the Yukon.

To date the viral strain of influenza currently circulating among tourists in all three jurisdictions appears to be A/Sydney/5/97 (H3N2)-like. This strain is covered by the 1998-99 influenza vaccine formulation as well as the 1999-2000 formulation.

Background

The risk of exposure to influenza during travel depends on the time of year, destination and type of travel (e.g., large, organized tourist groups). In the tropics, influenza can occur throughout the year. In temperate regions of the Southern Hemisphere, most activity occurs from April through September. In the Northern Hemisphere, influenza generally occurs from November through March.

Several factors may account for the emergence and spread of influenza and ILI early this summer. First, there has been an increasing volume of travellers from all over the world who visit this region, particularly on board cruise ships sailing the west coast, often in conjunction with land-based tours (by bus or train) in Alaska, British Columbia and the Yukon Territory.

Immunity to the strains of influenza virus covered by the vaccine-administered in the late fall or early winter - probably wanes after 4-6 months, which means that some vaccinated persons likely are susceptible again the following summer. Vaccinated persons remain susceptible to the influenza strains not covered by the vaccine, and to non-influenza organisms that cause ILI.

Another important factor is that on cruise ships, and on bus or train tours, large numbers of people co-exist in relatively confined spaces, which may facilitate the transmission of influenza and other respiratory organisms.

Finally, the demographic profile of the tourists may facilitate influenza transmission. Compared to the general population, there is usually a higher proportion of older adults travelling on cruise ships. While many may have had the influenza vaccine, the risk of serious complications from influenza infection is greater in a senior population.

Certain persons are at high risk for developing serious complications from influenza infection. The National Advisory Committee on Immunization (NACI) defines "people at high risk" as: people 65 years or older; adults and children with chronic cardiac or pulmonary disorders [e.g., cystic fibrosis and asthma] severe enough to require regular medical follow-up or hospital care; people of any age who are residents of nursing homes and other chronic care facilities; adults and children with chronic conditions such as diabetes and other metabolic diseases, cancer, immunodeficiency, immunosuppression, kidney disease, and certain blood disorders; children and adolescents with conditions treated for long periods with aspirin; persons infected with HIV; and people at high risk of influenza complications who are travelling to areas where influenza is likely to be circulating.

The cruise ship industry - following advice by Canadian and US public health authorities - has recognized in recent years the importance of reducing the risk of spread of influenza, for example, by having the ships' crews and hospitality staff vaccinated. The industry has also established ongoing surveillance and is prepared to provide appropriate measures to reduce the severity of illness among both passengers and crew.

Recommendations

To date, there continues to be no evidence of widespread transmission in the general population in Alaska, British Columbia or the Yukon Territory. Thus, Health Canada, British Columbia and the Yukon Territory public health authorities do not recommend influenza vaccination for the general population.

For persons travelling to Alaska or the Yukon Territory by any means of transportation, Health Canada does not recommend any specific precautions for the average traveller in good health at this time.

However, the aforementioned high-risk persons who are planning to travel to these areas should consult their personal physicians to assess their individual risk prior to travel. These are the same groups of persons for whom a routine annual "flu shot" is strongly recommended prior to the winter peak "flu" season.

Additional recommendations include:

• High-risk persons who did receive an influenza vaccine for the 1998-99 flu season will have waning levels of protection at present and should be offered revaccination with the 1998-99 vaccine. The current NACI Statement on Influenza Vaccination for the 1999-2000 Season acknowledges that "there is insufficient evidence at this time to advise in favour of or against routine re-immunization of travellers who were immunized in the fall, and who are subsequently travelling to regions where influenza may be circulating in the late spring and summer." Nevertheless, in the absence of specific evidence to the contrary, the benefits of revaccination may outweigh any disadvantages.
• Influenza vaccine should be administered at least 2 weeks before travel is undertaken since protective antibody levels require this amount of time to develop.
• Because the 1998-99 influenza season ends in March-April, only a limited supply of influenza vaccine is available. Canadians who are at high risk and plan to travel on cruise ships and/or take land-based tours to Alaska or the Yukon Territory should consult with their physicians or local public health authorities to obtain the vaccine.
• Persons who receive the 1998-99 influenza vaccine should be advised that it will not provide full protection for the coming 1999-00 influenza season and that revaccination will be required in the Fall.
• Target groups for influenza and pneumococcal vaccination overlap considerably. Health care providers should take the opportunity to administer pneumococcal vaccine to eligible persons (if they have not been vaccinated in the past 5 years) during the same visit at which influenza vaccine is given.
• As part of the pre-travel assessment of individuals at high risk of influenza complications, physicians should consider prescribing the antiviral medication amantadine that the travellers can take with them should they develop ILI symptoms. However, travellers who develop such symptoms are strongly encouraged to first consult a health care provider associated with the tour package, cruise ship, or local community. Amantadine is only effective against influenza A, which may be diagnosed by rapid-antigen detection kits. Guidelines for the dosage of amantadine can be found in NACI's Statement on Influenza Vaccination for the 1999-2000 Season, Canada Communicable Disease Report (1 June 1999), 25 (ACS-2): 1-13. This can be accessed electronically at : http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/99vol25/25sup/acs2.html