Cruise ship travel presents a unique combination of health concerns. Travelers from diverse regions brought together in often crowded, semi-enclosed environments onboard ships can facilitate the spread of person-to-person, foodborne, or waterborne diseases. Outbreaks on ships can be sustained for multiple voyages by transmission among crew members who remain onboard or by persistent environmental contamination. Port visits can expose travelers to local vectorborne diseases. The remote location of the travelers at sea means that they may need to rely on the medical capabilities and supplies available onboard the ship for extended periods of time, and cruise travelers and their physicians should be aware of ships’ medical limitations and prepare accordingly. Certain groups, such as pregnant women, the elderly, or those with chronic health conditions or who are immunocompromised, require special consideration when considering cruise travel.
CRUISE SHIP MEDICAL CAPABILITIES
Medical facilities on cruise ships can vary widely depending on ship size, itinerary, length of cruise, and passenger demographics. Generally, shipboard medical clinics can provide medical care comparable to that of ambulatory care centers. Although no agency officially regulates medical practice aboard cruise ships, consensus-based guidelines for cruise ship medical facilities were published by the American College of Emergency Physicians (ACEP) in 1995 and most recently updated in 2013. ACEP guidelines, which are followed by most major cruise lines, state that the cruise ship medical facilities should maintain the following minimum capabilities:
- Provide emergency medical care for passengers and crew
- Stabilize patients and initiate reasonable diagnostic and therapeutic interventions
- Facilitate the evacuation of seriously ill or injured patients
ILLNESSES AND INJURY ABOARD CRUISE SHIPS
Cruise ship medical clinics deal with a wide variety of illnesses and injuries. Approximately 3%–11% of conditions reported to cruise ship infirmaries are urgent or an emergency. Approximately 95% of illnesses are treated or managed onboard, and 5% require evacuation and shoreside consultation for medical, surgical, or dental problems. Roughly half of the passengers who seek medical care are older than 65 years of age. Most infirmary visits are due to acute illnesses, of which respiratory illnesses (19%–29%); seasickness (10%–25%); injuries from slips, trips, or falls (12%–18%); and gastrointestinal (GI) illness (9%–10%) are the most frequently reported diagnoses. Death rates for cruise ship passengers, most often from cardiovascular events, ranging from 0.6 to 9.8 deaths per million passenger-nights.
The most frequently reported cruise ship outbreaks involve respiratory infections, GI infections (norovirus), and vaccine-preventable diseases other than influenza, such as varicella (chickenpox). To reduce the risk of onboard introduction of communicable diseases by embarking passengers, ships may conduct medical screening during embarkation to identify ill passengers, preventing them from boarding or requiring isolation if they are allowed to board.
The following measures should be encouraged to limit the introduction and spread of communicable diseases on cruise ships:
- Passengers and their clinicians should consult CDC’s Travelers’ Health website before travel for updates on outbreaks and travel health notices.
- Passengers ill with communicable diseases before a voyage should delay travel until they are no longer contagious.
- Passengers who become ill during the voyage should seek care in the ship’s infirmary to receive clinical management, facilitate infection control measures, and maximize reporting of potential public health events.
SPECIFIC HEALTH RISKS
From 2008 through 2014, rates of GI illness among passengers on voyages lasting 3–21 days decreased from 27.2 to 22.3 cases per 100,000 travel days. Despite this decrease, GI illness outbreaks continue to occur.
More than 90% of GI outbreaks with a confirmed cause are due to norovirus. Characteristics of norovirus that facilitate outbreaks are a low infective dose, easy person-to-person transmissibility, prolonged viral shedding, no long-term immunity, and the organism’s ability to survive routine cleaning procedures. From 2010 through 2015, 8–16 outbreaks of norovirus infections occurred on cruise ships each year. GI outbreaks on cruise ships from food and water sources have also been associated with Salmonella spp., enterotoxigenic Escherichia coli, Shigella spp., Vibrio spp., Staphylococcus aureus, Clostridium perfringens, Cyclospora cayetanensis, and hepatitis A and E viruses.
To protect themselves from infections and reduce the spread of GI illnesses on cruise ships, passengers should be counseled on the following:
- Passengers should wash their hands with soap and water often, especially before eating and after using the restroom.
- Passengers who develop a GI illness, even if symptoms are mild, should promptly call the ship’s medical center (or the ship’s master, if no medical center exists) and follow cruise ship guidance regarding isolation and other infection control measures.
Respiratory illnesses are the most common medical complaint, and influenza is the most commonly reported vaccine-preventable illness on cruise ships. Since passengers and crew originate from all regions of the world, shipboard outbreaks of influenza A and B can occur year-round, and travelers on cruise ships can be exposed to strains circulating in different parts of the world. Using the 2008–2011 surveillance data, CDC found a mean rate of influenza-like illness (defined as temperature ≥100°F plus cough or sore throat) of 0.065 cases per 1,000 person-nights, without a detectable seasonal pattern.
Given the cruise ship environment, population, and variable medical capabilities, the following measures are recommended year-round to protect travelers from influenza:
- Clinicians should provide cruise travelers, particularly those at high risk for influenza complications, with the current seasonal influenza vaccine (if available) ≥2 weeks before travel.
- Passengers at high risk for influenza complications should discuss antiviral treatment and chemoprophylaxis with their health care provider before travel.
- Passengers should practice good respiratory hygiene and cough etiquette.
- Passengers should report their respiratory illness to the infirmary promptly and follow isolation recommendations if indicated.
Although it is not a common cause of respiratory illness on cruise ships, Legionnaires’ disease is a treatable infection that can result in severe pneumonia leading to death. More than 20% of all Legionnaires’ disease cases reported to CDC are travel-associated. Clusters of Legionnaires’ disease associated with hotel or cruise ship travel are difficult to identify because travelers often disperse from the source of infection before symptoms begin. A total of 83 ship-associated cases of Legionnaires’ disease were reported in the literature from 1977 through 2012. The cases involved outbreaks on 8 ships, with a median of 4 cases per outbreak (range, 2–50 cases); 6 cases resulted in death.
In general, Legionnaires’ disease is not transmitted person to person but is contracted by inhaling or aspirating warm, aerosolized water contaminated with Legionella organisms. Person-to-person transmission may be possible in rare cases. Contaminated ships’ hot tubs are the most commonly implicated sources of shipboard Legionella outbreaks; potable water supply systems have also been implicated. Improvements in ship design and standardization of water disinfection have reduced the risk of Legionella growth and colonization.
Most cruise ships have health care personnel who can perform Legionella urine antigen testing. People with suspected Legionnaires’ disease require prompt antibiotic treatment.
In evaluating cruise travelers for Legionnaires’ disease, clinicians should do the following:
- Obtain a thorough travel history of all destinations from 10 days before symptom onset (to assist in the identification of the potential source of exposure).
- Collect urine for antigen testing.
- Culture lower respiratory secretions on selective media, which is essential to identify the species or serogroup.
- Inform CDC of any travel-associated Legionnaires’ disease cases by sending an email to firstname.lastname@example.org. Cases of Legionnaires’ disease should be quickly reported to public health officials in order to determine if there are links to previously reported clusters and to stop potential clusters and new outbreaks.
Vaccine-Preventable Diseases (VPDs)
Although most cruise ship passengers are from countries with routine vaccination programs (such as the United States and Canada), many crew members originate from developing countries with low immunization rates. Outbreaks of measles, rubella, meningococcal disease and, most commonly, varicella have been reported on cruise ships. Preventive measures to reduce the spread of VPDs onboard cruise ships should be followed:
- Crew members should have documented proof of immunity to VPDs.
- Passengers, especially older passengers (>65 years of age) and immunocompromised people, should be up-to-date with routine vaccinations before travel, as well as any required or recommended vaccinations specific for their destinations.
- Women of childbearing age should be immune to varicella and rubella before cruise ship travel.
Cruise ship port visits may include countries where vector-borne diseases such as malaria, dengue, yellow fever, Japanese encephalitis, and Zika are endemic. New diseases might surface in unexpected locations. For example, chikungunya was reported in late 2013 for the first time in the Caribbean (with subsequent spread throughout the Caribbean and numerous North, Central, and South American countries and territories). Zika virus was first reported in Brazil in 2015 and subsequently spread across the Caribbean and Latin America. See Chapter 3 for additional information on specific vector-borne diseases.
Passengers should follow recommendations for avoiding mosquito bites and vector-borne infections:
- Use an effective insect repellent.
- Treat clothing and gear with permethrin or purchase permethrin-treated items.
- While indoors, remain in well-screened or air-conditioned areas.
- When outdoors, wear long-sleeved shirts, long pants, boots, and hats.
- Obtain yellow fever vaccination if recommended or required.
- Take antimalarial chemoprophylaxis if needed.
Other Health Concerns
Stresses of cruise ship travel include varying weather and environmental conditions, as well as unaccustomed changes in diet and physical activity. Foreign travel may increase the likelihood of risk-taking behaviors such as alcohol misuse, drug use, and unsafe sex. In spite of modern stabilizer systems, seasickness is a common complaint (affecting up to one-fourth of travelers). Cruise lines may not allow women to board after the 24th week of pregnancy, and pregnant women should contact the cruise line for specific policies and recommendations before booking.
PREVENTIVE MEASURES FOR CRUISE SHIP TRAVELERS
Cruise ship travelers often have complex itineraries due to multiple, short port visits. Although most of these port visits do not include overnight stays off the cruise ship, some trips have options for travelers to venture off the ship for ≥1 night. Therefore, cruise ship travelers may be uncertain about potential exposures and which antimicrobial prophylaxis, immunizations, and preventive measures should be considered. Box 6-01 summarizes recommendations for cruise travelers and clinicians advising cruise travelers in pretravel preparation and healthy behaviors during travel. Travelers with special medical needs, such as wheelchairs, oxygen tanks, or dialysis, should inform their cruise line before traveling. Travelers with health conditions should carry a written summary of essential health information (electrocardiogram, chest radiograph, if abnormal, blood type, chronic conditions, allergies, treating physician contact information, and medication list) that would facilitate their care during a medical emergency. In addition, all prospective cruise travelers should verify coverage with their health insurance carriers and, if not included, consider purchasing additional insurance to cover medical evacuation and health services in foreign countries
REPORTING ILLNESS AFTER TRAVEL
Travelers who become ill after returning home should inform their health care providers of where they have traveled. Clinicians should report suspected communicable diseases in recently returned cruise ship travelers to public health authorities:
- Report GI illnesses related to cruise ship travel to the CDC VSP by calling 800-CDC-INFO (800-232-4636) or by visiting www.cdc.gov and clicking on “Contact CDC-INFO” in the bottom right-hand corner.
- Inform CDC of any travel-associated Legionnaires’ disease cases by sending an e-mail to email@example.com.
- Report communicable diseases to their local public health authorities. Health departments should notify the CDC quarantine station of the jurisdiction for communicable diseases of public health concern during travel.
Source: Centers for Disease Control and Prevention: wwwnc.cdc.gov