Funding for this research was provided by:
shipping company Hamburg Süd “COLUMBUS” Ship management
Received: 8 August 2017
Accepted: 20 February 2018
First Online: 27 February 2018
Ethics approval and consent to participate
: The study protocol was approved by the Ethics committee of Medical Association Hamburg and conducted according to the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.
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