Respiratory infections in large passenger vessels

Introduction:
Respiratory tract infections are commonly documented on all passenger ship types, and attack rates in past outbreaks have affected as much as one-third of the onboard population^1-4. This systematic review aimed to understand risk factors, transmission dynamics and effectiveness of control measures for respiratory infections on large passenger ships.

Methods:
Conducted according to PRISMA 2020, peer-reviewed articles reporting human infectious disease events linked to passenger ships and seaports worldwide were eligible. Respiratory events were defined as: COVID-19 or other respiratory disease (excluding Legionnaire’s disease) described as a case, cluster or outbreak. Articles had to describe infection frequency with at least one case laboratory-confirmed. PubMed, Scopus and Cochrane Library were searched from January 2000 – March 2023.

Results:
The review identified 96 eligible publications. We analyzed 32 COVID-19 events among 32 ships (27 cruise, 2 river cruise, 2 expedition, 1 ferry) on 43 voyages (25 single voyage, 5 events on consecutive voyages) linked to 794 hospitalizations and 56 deaths^5-41. Presumed outbreak sources included: ill/incubating crew embarking and infected travelers continuing in subsequent voyages. A total of 31 studies reported control measures. We analyzed 13 influenza events (5 single voyage, 4 events on consecutive voyages) linked to 100 hospitalizations and 2 deaths^2,42-53. Presumed outbreak sources were most commonly infected incubating/ill traveler embarking; 5 events reported person-to-person transmission and 10 events reported control measures.

Conclusions:
Presumed outbreak sources highlight the importance of continuing control measures after an outbreak voyage, emphasizing surveillance of travellers continuing on subsequent voyages. Strength of evidence for risk factors varies, but demonstrates the need for strict compliance with individual isolation, supported by behavioural interventions. Defining effectiveness of individual measures is challenging; a multi-layered approach for measure implementation is recommended.

ACKNOWLEDGEMENTS

We would like to thank the HEALTHY SAILING project consortium.

CONFLICTS OF INTEREST

None declared.

FUNDING

HEALTHY SAILING project has received funding from the European Union’s Horizon Europe Framework Programme (HORIZON) under Grant Agreement number 101069764. Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Climate, Infrastructure and Environment Executive Agency (CINEA). Neither the European Union nor the granting authority can be held responsible for them. This work was funded by UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee [grant number 10040786], [grant number 10040720]. This work has received funding from the Swiss State Secretariat for Education, Research and Innovation (SERI).

ETHICAL APPROVAL AND INFORMED CONSENT

Ethical approval and informed consent were not required for this study.

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