Guidance for Cruise Ships on Influenza-like Illness (ILI) Management

Outbreaks of influenza and other respiratory viral diseases can occur at any time of the year among cruise ship passengers. Early detection, prevention, and control of influenza are important, not only to protect the health of travelers on cruise ships, but also to avoid spread of disease into home communities by disembarking sick passengers and crew members.

Purpose

This document provides guidance for cruise ships originating from, or stopping in, the United States to help prevent, diagnose, and medically manage influenza-like illness (ILI). This guidance to cruise ship clinics will be updated as needed. The US Centers for Disease Control and Prevention (CDC) recognizes that cruise ships travel worldwide, necessitating awareness of, and responsiveness to, local jurisdictional requirements. Cruise ship management and medical staff need to be flexible in identifying and caring for people with ILI. The healthcare provider’s assessment of a patient’s clinical presentation and underlying risk factors is always an essential part of decisions about the need for further medical evaluation, testing, and treatment.

This document also provides guidance for preventing spread of ILI during and after a voyage, including personal protective measures for crew members and control of outbreaks.

Reducing the Spread of Influenza

Commercial maritime travel is characterized by the movement of large numbers of people in closed and semi-closed settings. Like other close-contact environments, these settings can facilitate the transmission of influenza viruses and other respiratory viruses from person to person through droplet spread or potentially through contact with contaminated surfaces.

CDC recommends that efforts to reduce the spread of influenza and other respiratory diseases on cruise ships focus on encouraging crew members and passengers to

• Get vaccinated annually for influenza
• Postpone travel when sick
• Take everyday steps to protect themselves and others while traveling

Specific management should include early identification and isolation of crew members and passengers with ILI, encouraging good respiratory hygiene and cough etiquette, use of influenza antiviral medications for treatment of people with suspected or confirmed influenza, and use of antiviral chemoprophylaxis during influenza outbreaks, if indicated, for high-risk people exposed to influenza.

Influenza Vaccination of Crew and Passengers

CDC recommends that all people 6 months of age and older be vaccinated each year with the influenza vaccine.

Crew members should be vaccinated yearly. Vaccination of passengers, especially those at high risk for influenza complications, is recommended at least 2 weeks before cruise ship travel, if influenza vaccine is available and the person has not already been vaccinated with the current year’s vaccine. For more information on influenza vaccine recommendations, see Seasonal Influenza Vaccination Resources for Health Professionals.

Managing Passengers and Crew with Influenza-like Illness

Signs and symptoms of influenza include acute onset of some or all of these signs and symptoms: fever or feeling feverish, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache, fatigue (tiredness), and sometimes diarrhea or vomiting. Fever (a temperature of 100°F [37.8°C] or higher) will not always be present in people with influenza, especially not in elderly or immunosuppressed people. Cruise ship medical personnel should consider someone to have a fever if the sick person feels warm to the touch, gives a history of feeling feverish, or has an actual measured temperature of 100°F (37.8°C) or higher. Because the signs and symptoms of influenza are not specific and most people who have a respiratory illness are not tested for influenza, ILI has been defined for surveillance purposes as an illness with fever or feverishness plus either cough or sore throat in the absence of another diagnosis.

Sick people should be advised to seek health care if they are at high risk of developing severe illness from influenza or if they are concerned about their illness. People with underlying chronic medical conditions can experience exacerbation of those conditionsexternal icon with influenza.

Respiratory Hygiene and Cough Etiquette

People with ILI should be advised of the importance of covering coughs and sneezes with a tissue. Used tissues should be disposed of immediately in a disposable container (e.g., plastic bag) or a washable trash can. Passengers and crew members should be reminded to wash their hands often with soap and water, especially after coughing or sneezing. If soap and water are not available, they can use an alcohol-based hand sanitizer.

Managing Passengers or Crew with ILI upon Boarding and While Onboard

Any passenger who has ILI at the time of embarkation should be advised not to travel until at least 24 hours after resolution of fever without the use of fever-reducing medications (e.g., acetaminophen, ibuprofen, paracetamol). Aspirin should not be used to treat influenza signs or symptoms in children or adolescents younger than 19 years of age because of the risk of Reye syndrome.

Passengers with ILI who nonetheless decide to board, as well as passengers who become sick with ILI en route, should remain isolated in their cabins or quarters (with the exception of clinic visits, if needed), until at least 24 hours after resolution of fever without the use of fever-reducing medications.

Crew members with ILI should take the following actions:

• Notify their supervisors.
• Report to the infirmary for medical evaluation, according to shipboard protocols.
• Remain isolated in their cabins or quarters until at least 24 hours after resolution of fever without the use of fever-reducing medications.
• Continue to practice respiratory hygiene, cough etiquette, and hand hygiene after returning to work, because respiratory viruses can continue to be shed for several days after fever resolves.

Passengers and crew members who are in a high-risk group for complications from influenza or who are experiencing severe illness should seek medical care as soon as possible and be evaluated for possible influenza testing and antiviral treatment.

While temporarily in common areas, passengers and crew members with ILI should be encouraged to remain as far away from others as possible (at least 6 feet), and either wear face masks or cover their mouths and noses with a tissue.

Managing Passengers or Crew with ILI upon Disembarkation

A disembarking cruise ship passenger or crew member who has ILI or who has had fever within the 24 hours before disembarking should be advised to take the same precautions: to stay inside home or hotel in the city of disembarkation and to refrain from further travel until at least 24 hours after he or she is free of fever without the use of fever-reducing medications.

If a passenger or crew member with ILI is taken to a healthcare facility off the ship, the facility should be informed before arrival.

Managing Passengers and Crew Following Exposure to a Person with ILI

Passengers and crew members who may have been exposed to a person suspected of having influenza should monitor their health for 4 to 5 days after the exposure. Passengers and crew members who develop ILI while still on board should notify the shipboard infirmary immediately and remain isolated in their cabins or quarters until at least 24 hours after resolution of fever without the use of fever-reducing medications. Sick travelers should be advised to seek healthcare if they are at high risk of developing severe illness from influenza or if they are concerned about their illness.

Medical Evaluation and Management

For more information, read updated resources for clinicians and guidance on the medical evaluation and management of people with influenza, available on CDC’s influenza website.

Influenza Diagnostic Tests

CDC’s influenza website also includes recommendations for the clinical use of influenza diagnostic tests, information on available tests, specimen collection, and guidance on interpretation of influenza testing results. Respiratory specimens should ideally be collected within 3 to 4 days of illness onset. The Infectious Diseases Society of Americaexternal icon recommends use of rapid influenza molecular assays in outpatients with suspected influenza and provides recommendations for respiratory specimen collection and influenza testing.

Healthcare providers should understand the advantages and limitations of influenza tests, and proper interpretation of negative results of rapid influenza diagnostic tests (antigen detection tests). Rapid influenza diagnostic tests without an analyzer device have low to moderate sensitivity compared with RT-PCR, and false negative results can occur frequently. Rapid influenza diagnostic tests that use a digital analyzer reader device have moderately high sensitivity compared with RT-PCR, but false negative results can still occur. Negative rapid influenza diagnostic test results do not exclude a diagnosis of influenza; clinical diagnosis of influenza should be considered; however, positive test results are useful to establish a diagnosis of influenza and to provide evidence of influenza in passengers and crew members aboard ships.

Use of Antiviral Treatment and Chemoprophylaxis for People at High Risk for Complications

Early antiviral treatment with neuraminidase inhibitors (oral oseltamivir, inhaled zanamivir or IV peramivir) is recommended for people with suspected or confirmed influenza who have severe illness or are at high risk for influenza complications, including people with asthma, diabetes, and heart disease.

Baloxavir marboxil is a new antiviral medication with a different mechanism of action from the neuraminidase inhibitors, and is approved for early treatment of uncomplicated influenza in people aged 12 years and older. A single oral dose of baloxavir is equivalent to 5 days of twice daily oral oseltamivir; however, baloxavir is not recommended for pregnant women, lactating mothers, or people with severe influenza, including hospitalized patients, because of the lack of data in these groups. Antiviral treatment recommendations are available.

Antiviral treatment also can be considered, on the basis of clinical judgment, for outpatients with uncomplicated, suspected, or confirmed influenza who are not known to be at increased risk for developing severe or complicated illness if antiviral treatment can be initiated within 48 hours of illness onset; treatment of these cases may be particularly advisable in an outbreak setting on a cruise ship.

Antiviral chemoprophylaxis can be considered for prevention of influenza in exposed people who are at high risk for complications or could be given to all contacts on a cruise ship when the outbreak threshold is met or exceeded. Additional information about antiviral chemoprophylaxis is available per the Infectious Diseases Society of Americaexternal icon guidelines.

Outbreak Control

A combination of measures can be implemented to control influenza outbreaks, including isolation and early antiviral treatment of sick people, infection control efforts, antiviral chemoprophylaxis of exposed people, crew member and passenger notifications, and active surveillance for new cases. Recommendations for controlling institutional influenza outbreaks are available per the Infectious Diseases Society of Americaexternal icon guidelines.

Preventing Influenza in Crew Members

In addition to annual influenza vaccination, the following recommendations should be followed, when possible, by crew members whose work activities involve contact with passengers and other crew members who have ILI.

• Maintain a distance of 6 feet from the sick person while interviewing, escorting, or providing other assistance.
• Keep interactions with sick people as brief as possible.
• Limit the number of people who interact with sick people. To the extent possible, the sick person should receive care and meals from a single person.
• Avoid touching your eyes, nose, and mouth.
• Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand sanitizer.
• Ask the sick person to consider wearing a face mask, and provide one, if wearing it can be tolerated.
• Provide tissues and access to soap and water and ask the sick person to:
  • Cover his or her mouth and nose with a tissue (or face mask) when coughing or sneezing.
  • Throw away used tissues immediately in a disposable container (plastic bag) or a washable trash can.
  • Wash his or her hands often with soap and water for 20 seconds.
    • If soap and water are not available, the sick person should use an alcohol-based hand sanitizer.

Reporting

CDC requests that cruise ships submit a cumulative ILI report (even if no deaths or ILI cases have occurred) preferably during the final 24 hours of the voyage or as soon as an outbreak is suspected, as described below. These reports should be made once per voyage by completing the one-page Maritime Conveyance Cumulative Influenza/Influenza-like Illness (ILI) Formpdf icon and clicking on the gray “Send Via Email” box in the top left corner.

CDC requests that cruise lines immediately report any of the following events to the CDC Quarantine Station having jurisdiction over the next US port of entry:

• Outbreaks of influenza or ILI (exceeding 1.380 cases per 1,000 traveler days) among passengers or crew members (instructions for calculating ILI threshold are available on the CDC Quarantine and Isolation website)
• Hospitalization (ashore or at sea) caused by, or suspected to be associated with, influenza or ILI onboard the vessel

In addition, CDC emphasizes that any death, including those caused by or suspected to be associated with influenza or ILI, that occurs aboard a cruise ship destined for a US port must be reported to CDC immediately. Report ILI hospitalizations or deaths by submitting an individual Maritime Conveyance Illness or Death Investigation Formpdf icon for each hospitalization or death, or report by phone.

Vessel captains may request assistance from CDC to evaluate or control influenza outbreaks as needed. If the ship will not be arriving imminently at a US seaport, CDC quarantine officials will provide guidance to cruise ship officials regarding management and isolation of the sick person or people and recommendations for other passengers and crew members. Before the ship arrives, inform the respective CDC Quarantine Station if any support is needed, including hospitalization of sick people and laboratory testing of clinical specimens.

For influenza cases requiring hospitalization, CDC quarantine officials will work with the cruise line and local and state health departments to facilitate medical transportation of the patient upon arrival. In outbreak situations, CDC staff may also help with disease control and containment measures, passenger and crew notification, surveillance activities, communicating with local public health authorities, obtaining and testing laboratory specimens, and provide additional guidance as needed.

For ships on international voyages, if an illness occurred on board, the Maritime Declaration of Health should be completed and sent to the competent authority, according to the 2005 International Health Regulations and the national legislation of the country of disembarkation. Before entering a seaport, cruise ships may also be required to report the ship’s previous itinerary.

Additional Recommendations

Personal Protective Equipment

Crew members and other staff who may have contact with people with ILI should be instructed in the proper use, storage, and disposal of personal protective equipment (PPE). Improper use or handling of PPE can increase disease transmission risk.

Crew members should wear impermeable, disposable gloves if they need to have direct contact with sick people or potentially contaminated surfaces, rooms, or lavatories used by sick passengers and crew members. Crew members should wash their hands with soap and water or use an alcohol-based hand sanitizer after removing gloves. Used gloves should be discarded in the trash and should not be washed or saved for reuse. Crew members should avoid touching their faces with gloved or unwashed hands.

Use of N95 respirators or face masks is not generally recommended for cruise ship crew members for general work activities. Use of face masks can be considered for cruise ship workers who cannot avoid close contact with people with ILI. Crew members who use N95 respirators should receive annual fit testing. Crew members who provide health care to passengers or other crew members (e.g., onboard nurses and physicians) should follow CDC’s prevention strategies for seasonal influenza in health care settings.

Supplies

Ships should ensure availability of conveniently located dispensers of alcohol-based hand sanitizer.  Where sinks are available, ships should ensure that supplies for handwashing (i.e., soap, disposable towels) are consistently available.

Ships should carry a sufficient quantity of PPE, such as face masks, N95 respirators, and disposable gloves, for use in controlling the spread of influenza or other diseases.

Ships should carry a sufficient quantity of medical supplies to meet day-to-day needs. Contingency plans are recommended for rapid resupply during outbreaks. Stocking oral oseltamivir and inhaled zanamivir for antiviral treatment or chemoprophylaxis of influenza virus infection is recommended.

Ships are encouraged to carry sterile viral transport media and sterile swabs to collect nasopharyngeal and nasal specimens. These optimal recommendations can be modified to reflect individual ship capabilities and characteristics.

Cleaning and Disinfection

During influenza outbreaks, in addition to routine cleaning and disinfection strategies, cruise ships may consider more frequent cleaning of commonly touched surfaces such as handrails, countertops, and doorknobs. Surfaces contaminated by the respiratory secretions of a sick person (e.g., in the sick person’s living quarters or work area, and in isolation rooms) should also be cleaned. The primary mode of influenza virus transmission is believed to be through respiratory droplets that are spread from an infected person through coughing or sneezing to a susceptible close contact within about 6 feet; therefore, widespread disinfection to control influenza outbreaks is unlikely to be effective.

References

1. Cruise ships: high-risk passengers and the global spread of new influenza viruses.external icon
   Miller JM, Tam TW, Maloney S, Fukuda K, Cox N, Hockin J, Kertesz D, Klimov A, Cetron M.
   Clin Infect Dis. 2000 Aug;31(2):433-8.
2. Influenza B virus outbreak on a cruise ship–Northern Europe, 2000.external icon
   Centers for Disease Control and Prevention (CDC).
   MMWR Morb Mortal Wkly Rep. 2001 Mar 2;50(8):137-40.
3. Large summertime influenza A outbreak among tourists in Alaska and the Yukon Territory.external icon
   Uyeki TM, Zane SB, Bodnar UR, Fielding KL, Buxton JA, Miller JM, Beller M, Butler JC, Fukuda K, Maloney SA, Cetron MS; Alaska/Yukon Territory Respiratory Outbreak Investigation Team.
   Clin Infect Dis. 2003 May 1;36(9):1095-102.
4. Update: outbreak of influenza A infection–Alaska and the Yukon Territory, July-August 1998.external icon
   Centers for Disease Control and Prevention (CDC).
   MMWR Morb Mortal Wkly Rep. 1998 Aug 28;47(33):685-8.
5. Outbreak of influenza A infection–Alaska and the Yukon Territory, June-July 1998.external icon
   Centers for Disease Control and Prevention (CDC).
   MMWR Morb Mortal Wkly Rep. 1998 Aug 7;47(30):638.
6. Outbreak of influenza A infection among travelers–Alaska and the Yukon Territory, May-June 1999.external icon
   Centers for Disease Control and Prevention (CDC).
   MMWR Morb Mortal Wkly Rep. 1999 Jul 2;48(25):545-6, 555.
7. Update: Influenza activity — United States, 1997-98 season.external icon
   Centers for Disease Control and Prevention (CDC).
   MMWR Morb Mortal Wkly Rep. 1997 Nov 21;46(46):1094-8.
8. Acute respiratory illness among cruise-ship passengers–Asia.external icon
   Centers for Disease Control (CDC).
   MMWR Morb Mortal Wkly Rep. 1988 Feb 5;37(4):63-6.
9. Outbreak of influenza-like illness in a tour group–Alaska.external icon
   Centers for Disease Control (CDC).
   MMWR Morb Mortal Wkly Rep. 1987 Oct 30;36(42):697-8, 704.
10. Presumptive summer influenza A: an outbreak on a trans-Tasman cruise.external icon
    Ferson M, Paraskevopoulos P, Hatzi S, Yankos P, Fennell M, Condylios A.
    Commun Dis Intell. 2000 Mar 16;24(3):45-7.
11. Outbreak of 2009 pandemic influenza A (H1N1) on a Peruvian Navy ship – June-July 2009.external icon
    Centers for Disease Control and Prevention (CDC).
    MMWR Morb Mortal Wkly Rep. 2010 Feb 19;59(6):162-5.
12. Outbreak of influenza in a highly vaccinated crew of U.S. Navy ship.external icon
    Earhart KC, Beadle C, Miller LK, Pruss MW, Gray GC, Ledbetter EK, Wallace MR. Emerg Infect Dis. 2001 May-Jun;7(3): 463-5.
13. Preparedness for the prevention and control of influenza outbreaks on passenger ships in the EU: The SHIPSAN TRAINET project communication.external icon
    Mouchtouri VA, Black N, Nichols G, Paux T, Riemer T, Rjabinina J, Schlaich C, Menel Lemos C, Kremastinou J, Hadjichristodoulou C, Collective for SHIPSAN TRAINET project.
    2009 May 28;14(21):1-4.
14. The decision making process on public health measures related to passenger ships: the example of influenza pandemic 2009.external icon
    Mouchtouri VA, Bartlett CL, Jaremin B, Nichols G, Paux T, Riemer T, Black N, Varela-Martinez C, Swaan CM, Schlaich C, Rachiotis G, Kremastinou J, Hadjichristodoulou C, Collective for SHIPSAN TRAINET project. Int. Marit. Health. 2010;62(4):241-5.
15. Retrospective investigation of an influenza A/H1N1pdm outbreak in an Italian military ship cruising in the Mediterranean Sea, May-September 2009.external icon
    Tarabbo M, Lapa D, Castilletti C, Tommaselli P, Guarducci R, Lucà G, Emanuele A, Zaccaria O, La Gioia VF, Girardi E, Capobianchi MR, Ippolito G.
    PLoS ONE 6(1): e15933. doi:10.1371/journal.pone.0015933.
16. Clinical practice guidelines by the Infectious Diseases Society of America: 2018 update on diagnosis, treatment, chemoprophylaxis, and institutional outbreak management of seasonal influenzaexternal icon.
    Uyeki TM, Bernstein HH, Bradley JS, Englund JA, File TM, Fry AM, Gravenstein S, Hayden FG, Harper SA, Hirshon JM, Ison MG, Johnston BL, Knight SL, McGreer A, Riley LE, Wolfe CR, Alexander PE, Pavia AT.Clin Infect Dis. 2018 Dec 19;36(9):1095-102. doi: 10.1093/cid/ciy866. [Epub ahead of print]