key: cord-0712492-8oyihpm6
authors: Aoki, Yoshihiro; Amaya Dimas, Liliana del Carmen
title: Influenza epidemic on a world cruise ship: A descriptive study
date: 2021-10-21
journal: Travel Med Infect Dis
DOI: 10.1016/j.tmaid.2021.102176
sha: a7e0dcd188cac598bc4b491e21f7ef189f043bdb
doc_id: 712492
cord_uid: 8oyihpm6

nan

The emergence of coronavirus disease (COVID-19) has shown that there is an urgent need to revise the health measures against communicable diseases on board cruise ships. Many influenza outbreaks related to cruise travel have been reported previously [1, 2] . We believe there is room to improve the current guidelines to better prevent future outbreaks of influenza on board cruise ships. We conducted a prospective cohort study analyzing the association between underlying disease and serious events on a world cruise ship [3] . Under this setting, we performed a descriptive study of influenza on board a cruise ship before the start of the COVID-19 pandemic. This study was approved by the institutional ethics committee (institutional review board number 2020-017). Of the study patients, two pediatric patients have previously been reported separately, with a discussion on a potential pediatric treatment option [4] .

The study was conducted from September to December 201X (105 days) on a world cruise ship chartered by a Japanese travel agency. Passengers stayed in cabins designated for one, two, or four passengers, using restaurants, bars, halls, a gym, and public bathrooms during the voyage. Diagnosis was made clinically or using a rapid diagnostic antigen test based on the guideline for managing influenza-like illness (ILI) on cruise ships by United States Centers for Disease Control and Prevention (CDC) [5] . Antiviral drugs were administered to all confirmed patients with influenza to avoid an outbreak. Patients were immediately isolated in dedicated cabins after a diagnosis of influenza and were prohibited from leaving the cabin 24 hours after becoming afebrile. The crews in charge of serving and cleaning the isolation cabins were removed from service to other passengers. After the initial influenza diagnosis, sanitization measures on board were strengthened. Posters and newspapers were distributed, calling attention to infection prevention measures, including wearing a mask, hand hygiene, and early consultation with a physician if symptoms were experienced. For all patients, close contacts including passengers in the same cabin were confirmed by interview in the infirmary, and a health condition check was conducted by the physician for the passengers with direct exposure.

Passengers with direct exposure to the infected patients were recommended to take antiviral prophylaxis.

Of the 1275 passengers on board (median age 64.0 years, male 38.1%), 34 confirmed influenza patients were identified (2.7%). All infections occurred within 18 days, beginning on day 78 of the voyage and ending on day 95 (Fig. 1) . The initial patient was diagnosed with influenza on day 78, one day after leaving Port Said, Egypt. The patient attended the bus tour to Cairo from the port. The median age of the patients was 67.0 (interquartile range [IQR], 30.8-72.3) years and 29.4% were male. Thirty-three patients (97.1%) were Japanese. Seventeen patients (50.0%) had at least one underlying disease; the most common were hypertension (n = 7, 20.5%), dyslipidemia (n = 7, 20.5%), and diseases treated by anticoagulants or antiplatelets (n = 4, 11.8%). Only one patient (2.9%) had been vaccinated against seasonal influenza within two months of boarding. The median duration from the first onset of symptoms to diagnosis was 13 hours (IQR, 12.3-17.4 hours). Cough was the most common clinical symptom (n = 30, 88.2%), followed by fever (n = 29, 85.3%) and malaise (n = 28, 82.4%). Only one patient (2.9%) developed dyspnea at the time of consultation. The diagnosis was made clinically in five patients (14.7%) and by rapid diagnostic antigen test in the remaining 29 patients (85.3%). All rapid diagnostic antigen test results showed influenza A.

Oseltamivir was the selected antiviral agent in 13 patients (38.2%) and laninamivir in 21 patients (61.8%). The median isolation period was 52 hours (IQR, 47.1-71.5 hours). Antibiotics were administered to two patients (5.9%) with pneumonia and one patient (2.9%) with sinusitis due to secondary bacterial complications. One patient (2.9%) who experienced a bronchial asthma attack was treated with corticosteroids. A cerebrovascular event (suspected to be a transient ischemic attack) was observed in one patient (2.9%). There were no cases with serious outcomes requiring consultation ashore or emergency disembarkation. We recommended chemoprophylaxis to 52 passengers who had been in close contact with patients, including sharing a cabin with or having direct exposure to infected patients, but only 19 passengers (36.5%) accepted the offer. Most candidates declined chemoprophylaxis due to financial concerns. Oseltamivir and laninamivir were used as the antiviral agents for chemoprophylaxis in eight (42.1%) and 11 (57.9%) patients, respectively. All patients who received chemoprophylaxis remained disease-free. Three passengers who declined chemoprophylaxis subsequently developed the disease. The detailed route of infection was unable to be identified in 28 patients (82.4%) due to the lack of an onboard contact tracing system.

In this cruise, the CDC guidance for cruise ships on ILI management was useful in advancing infection control on board with limited resources; however, the infection still spread to 2.7% of passengers. In future cruises, it will be necessary to establish a method for elucidating the route of infection and tracing all passengers with direct exposure as a routine measure for managing onboard outbreaks. Cruise companies or travel agencies may want to consider financially covering post-exposure prophylaxis to prevent future outbreaks. Treatment options for critically ill patients on board are generally limited; therefore, in addition to the aggravation of influenza, attention should be paid to the possibility of complications.

There are some limitations to this study. First, the number of cases could be underestimated because it is possible that some ill passengers did not visit the infirmary. Second, this study was conducted before the beginning of the COVID-19 pandemic; therefore, the guidelines on prevention measures need to be updated to take COVID-19 transmission into account. Finally, data regarding history of influenza vaccination was obtained immediately before boarding, and therefore the number of patients vaccinated within one year may have been higher than reported.

Influenza outbreaks remain a serious problem on cruise ships. Preventive measures, such as vaccinations before boarding, adjusting guidelines to each vessel's environment, post-exposure chemoprophylaxis, and contact tracing systems, should be used to decrease the likelihood of an outbreak, and to contain the spread of influenza if an outbreak occurs.

Perusing the potentially relevant literature and drafting the initial manuscript (YA). Critically reviewing and revising the manuscript (LDCAD). Each author listed in the manuscript has seen and approved the submission of this version of the manuscript and takes full responsibility for the manuscript.

This work was not supported by any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

The authors have no conflicts of interest to declare. The first author was employed by the Japanese travel agency that chartered the cruise ship for the cruise described in this manuscript.

Outbreaks of pandemic (H1N1) 2009 and seasonal influenza A (H3N2) on cruise ship

Influenza B outbreak on a cruise ship off the São Paulo coast, Brazil

Association between underlying disease and serious events on a world cruise ship: a prospective cohort study

Reconstitution of oseltamivir capsules for pediatric use on a long-term cruise: a treatment option

Centers for Disease Control and Prevention Guidance for cruise ships on influenzalike illness (ILI) management

We are grateful to Ms. Stephani Retno Palupi for onboard patient management. We would like to thank Editage (www.editage.jp) for English language editing.