Recommendations for Cruise Lines to Help Reduce Risk of Measles Transmission

Measles is a serious and highly contagious disease. Since late 2018, the World Health Organization has reported a resurgence in measles cases worldwide. This global trend coincides with declining measles vaccination rates in many countries, which may be contributing to the spread of the disease. In 2019, CDC reported the greatest number of measles cases since measles was declared eliminated in the United States in 2000.

Purpose

CDC created these recommendations specifically for cruise ship clinicians and captains, and cruise line medical directors to help reduce the risk of measles introduction and transmission on cruise ships.

These recommendations can help protect passengers, crew, visiting corporate staff, and communities ashore when someone on board is suspected of being sick with measles. These recommendations include ensuring cruise line staff are protected against measles and encouraging passengers to get vaccinated prior to boarding if they are not immune to measles.

CDC also is providing contingency recommendations for detecting, managing, and reporting suspected measles cases on cruise ships destined for US ports, and managing exposed passengers and crew.

Broader CDC guidance on managing and reporting sick travelers aboard ships is available on the Maritime Resources webpage.

Key points

• Travelers (both passengers and crew) can avoid becoming infected and prevent the spread of measles by being fully vaccinated against measles (2 doses for international travelers at least 28 days apart, at least 2 weeks before travel), or by having other evidence of immunity against measles.
• Travelers (both passengers and crew) should not board a ship if they are sick, and measles is suspected.
• Cruise ship crew members should be vigilant for onboard travelers sick with fever and rash or other signs of measles (see “Measles disease” box). Take steps to minimize onboard transmission, as outlined below.
• Cruise ship medical staff who suspect measles in a traveler should report the illness to CDC as soon as possible before arrival at a US port.

Recommendations for Measles Prevention

Cruise lines should consider implementing policies that incorporate the following recommendations.

Measles education and awareness

a. Among crews

Cruise lines should ensure their crew members are aware of the

• Global risk of measles during international travel
• Signs and symptoms that may indicate a sick traveler has measles
• Strategies the ship’s medical staff can take to reduce the risk of onboard measles transmission
• Requirement for the cruise ship’s medical unit to report a traveler with suspected or known measles to CDC
• Benefits of vaccination
  • Recommend employees who don‘t have presumptive evidence of immunity to be fully vaccinated against measles
  • For international travel, adults are considered fully vaccinated when they have record of receiving two doses of measles-containing vaccine at least 28 days apart
• Importance of not working on a ship while sick with fever, especially if a rash is present

Cruise lines should also review their sick leave polices and communicate them to employees.

b. Among passengers

Cruise lines should consider communication strategies to encourage passengers to

• Be fully vaccinated against measles before travel, or have other evidence of measles immunity.
• Delay travel if they are sick with fever and a rash. Passengers who have a measles diagnosis must not travel until a doctor clears them for travel.

Cruise lines can help sick travelers delay travel

People should not travel if they have a fever and a rash or have a measles diagnosis, until a doctor clears them for travel. Health officials may also ask travelers who were exposed to measles and are not immune to delay travel until they are no longer at risk of becoming infectious. Travelers are more likely to comply in delaying travel for public health reasons if cruise lines allow passengers to modify their itineraries when they are known or suspected to have measles, or if public health officials have advised them to delay travel.

Immunity to measles among crew

Cruise lines should consider ensuring all ship crew and other employees who may travel internationally have presumptive evidence of immunity to measles.

• Maintain documentation of immune status of all employees.
• To the extent possible, minimize barriers to crew vaccination, for example, by ensuring adequate stock of MMR in ships’ medical centers and by offering MMR vaccines to employees.

Diagnostic laboratory testing needed

Laboratory confirmation should be sought for all suspected cases. Upon receiving a report from the ship’s medical staff of suspect measles in a passenger or crew member, the CDC Port Health Station with jurisdiction for the next US port of entry will inquire if measles virus testing is feasible in the vicinity of the port. If testing is feasible, the Port Health Station will work with the ship, state or local health department, and other health partners to ensure proper specimen collection and transport to the testing laboratory. If necessary, arrangements may be made for testing in another location.

Detecting measles-specific IgM antibody in serum and measles RNA by real-time polymerase chain reaction (RT-PCR) in respiratory specimens (throat or nasopharyngeal swab samples) are the most common methods for confirming measles infection. Urine samples may also contain virus (detectable by RT-PCR). When feasible to do so, collecting both respiratory and urine samples, in addition to serum, can increase the likelihood of detecting measles virus.

The Council of State and Territorial Epidemiologists’ case definitions for measles are available online. 

Presumptive evidence of immunity to measles

Acceptable presumptive evidence of immunity to measles includes at least one of the following:

• Written documentation of adequate vaccination:
  • 1 or more doses of a measles-containing vaccine administered on or after the first birthday for preschool-age children and adults not at high risk
  • 2 doses of measles-containing vaccine for school-age children and adults at high risk, which includes college students, healthcare personnel, and international travelers
• Laboratory evidence of immunity
• Laboratory confirmation of measles
• Birth in the United States before 1957

Managing travelers with known or suspected measles

Because cruise ships typically do not have onboard diagnostic capability for measles, activities to control transmission of possible measles on the ship need to start before the laboratory results are known. There is no specific antiviral therapy for measles. Immunoglobulin is not indicated for the treatment of patients with suspected or confirmed cases of measles. Supportive medical care helps relieve symptoms and address complications.

Instruct crew members and passengers to take these actions if they develop signs or symptoms of measles:

• Self-isolate in their cabins with the door closed.
• Call the ship’s medical unit and arrange for medical evaluation, possibly in their cabins to avoid exposing others.
  • Crew members should notify their supervisor and report their illness to the ship’s medical unit, according to shipboard protocols.

Sick crew members suspected of having measles should remain isolated in their cabins with the door closed or the ship’s medical unit in designated single-patient isolation rooms, as ordered by medical staff according to shipboard protocols.

An isolation room with negative air pressure capacity (also known as an airborne infection isolation room) is preferred for any patient with known or suspected measles. If that is not available, a cabin without other occupants can be used— away from other cabins to the extent possible and with the door closed. Place a facemask on the patient if tolerated, particularly when not in an isolation room or when being moved. If a facemask is not available, ask the sick person to cover their mouth and nose with tissues when coughing. After the patient leaves the room, it should remain vacant for at least two hours, because measles can survive in the air for up to two hours.

Isolate crew members and passengers while infectious (that is, for 4 days after the beginning of the rash, with rash onset as Day 0). On Day 5, no movement restrictions are necessary.

Minimize other passengers’ and cabin crew’s contact with the sick person. While infectious, the sick person should not share space with any infants or people who may have a weakened immune system, or pregnant women without known immunity to measles. If possible, designate one crew member with presumptive evidence of immunity to measles to serve the sick person. Cruise lines should be aware of employees’ measles immunity status. See CDC’s vaccine recommendations for healthcare personnel [PDF – 48 pages].

Regardless of immune status, all ship medical staff should wear gloves and respiratory protection at least as protective as a NIOSH certified N-95 respirator[1] when entering the isolation room of a sick traveler suspected of having measles. Because of the low but possible risk of vaccine failure in healthcare professionals exposed to infected patients, all medical staff should use respiratory protection when caring for patients with known or suspected measles. See CDC guidance on transmission-based precautions.

[1] Respirator use must be in the context of a complete respiratory protection program including medical clearance, fit testing, and training. Refer to Appendix B in the Interim Infection Prevention and Control Recommendations for Measles in Healthcare Settings for more information about respirators

Managing sick travelers upon disembarkation

Unless they are critically ill, ensure sick travelers who are in the infectious period disembark the ship last if they have suspected measles to reduce possibility of exposing others. The sick person should wear a facemask, if tolerated, during disembarkation. For those patients requiring transfer to a hospital, the cruise ship should notify emergency medical services and the admitting medical facility before arrival, and arrange for medical transportation to the facility with infection control precautions in place. The CDC Port Health Station will notify port partners and the local health department that a traveler with suspected measles will disembark to help coordinate transportation to the medical facility for evaluation and management.

Movement of travelers with suspected measles to any location other than a hospital, such as a private home or hotel, should be coordinated in advance with the local health department. Notify the CDC Port Health Station of any person with suspected measles who intends to travel by commercial airline or other public means after disembarkation.

Managing travelers after possible exposure

For suspected or confirmed measles cases, the CDC Port Health Station of jurisdiction can provide specific recommendations about identifying contacts, assessing for measles immunity, providing post-exposure prophylaxis to susceptible contacts, and performing surveillance for additional cases. Notify the CDC Port Health Station of any susceptible contacts who intend to travel by commercial airline or other public means after disembarkation.

Vaccine and immune globulin as post-exposure prophylaxis

Post-exposure prophylaxis (PEP) with MMR vaccine administered within 72 hours of initial exposure, or immune globulin (IG) within 6 days of exposure, may provide protection or modify the clinical course of disease among susceptible exposed contacts. The decision to administer vaccine or IG depends on several factors. These factors include the degree of clinical suspicion for measles in the source patient (or availability of laboratory confirmation), risk factors for more severe disease in exposed and susceptible persons, epidemiologic information about the intensity and duration of the exposure, contraindications to vaccination among exposed people, and the ship’s vaccine and IG supplies.

IG is recommended for people at risk of severe illness and complications from measles or when vaccine is contraindicated. This includes infants younger than 12 months, pregnant women without evidence of measles immunity, and persons with immunocompromising conditions. For infants aged 6 through 11 months, MMR vaccine can be given in place of IG, if administered within 72 hours of exposure. Do not administer MMR vaccine and IG simultaneously, as this practice invalidates the vaccine. CDC has posted more detailed guidance about PEP for measles.

People who receive PEP should still be monitored for signs and symptoms consistent with measles. Persons who received MMR should be monitored for 1 incubation period (21 days), and persons who received IG should be monitored for 28 days (due to possible prolongation of the incubation period), after the last possible exposure.

Exclusion of nonimmune exposed crew

Cruise lines should consider establishing a policy to exclude exposed crew members who are not healthcare personnel from working near passengers or other crew members if the exposed crew member

• has no presumptive evidence of measles immunity, and
• did not receive PEP (vaccine or IG) during the recommended time frames.

Exclusion is recommended starting on Day 5 after the first possible exposure through Day 21 after the last possible exposure.

Exclude shipboard healthcare personnel without evidence of immunity from duty from Day 5 after first exposure to Day 21 after last exposure, regardless of PEP.

Reporting suspected cases of measles

The US Code of Federal Regulations (CFR) Title 42, Part 71 requires ship captains to report all deaths and certain illnesses to the CDC Port Health Station at or nearest the next US port of arrival. Report deaths and certain illnesses—including fever and rash—before arrival at the next port or as soon as recognized.

The Maritime Conveyance Illness or Death Investigation Form [PDF – 4 pages] is the preferred method of reporting suspect cases of measles to CDC. Ships may submit this form by email, fax, or phone. See instructions on CDC’s webpage: Reporting Death or Illness on Ships.

CDC assistance

CDC can help cruise lines in their response to measles cases or an outbreak aboard a ship. You may contact the closest CDC Port Health Station, or email CDC’s Maritime Activity at maritimeadmin@cdc.gov.