Background: First, this analysis was conducted to study a coronavirus disease 2019 (COVID-19) cluster dynamic on a cruise ship in order to allow the ship physician to anticipate the duration and importance of the contaminations. Secondly, the author tries to find out if the closed environment on board allows specific conclusions about epidemic dynamics and preventative measures.
Materials and methods: From a personal epidemiological compendium done by himself on board the author analysed different epidemic curves identified on board other ships and compared them to the epidemiologic data from the different COVID-19 contamination waves in France since 2020. All crew members were submitted to polymerase chain reaction tests on D2, D5, D8 and D15 and symptomatic cases were tested on on-board devices in the meantime. An excel file called "Log Covid" allowed for daily reporting to the ship-owner on the epidemic dynamics and the prospects on the end of crises in order to anticipate the resumption of the business in the best conditions. The jobs on board, age and geographic origin of the contaminated people were analysed, as well as their vaccination status.
Results: Out of a total of 118 crew members, 61 (52%) sailors were contaminated in 8 days. The symptoms were benign (pharyngitis, headaches, feverish state); no serious form of illness were reported. The passengers were repatriated to France at the earliest stage. The epidemic phase occurred in a 15-day window. The first 8 days corresponded to the ascending phase, then a faster phase of epidemic decrease of 7 days. Similarities emerged between the epidemic dynamics of this virus and other contaminations on cruise ships and epidemic phases on land in spite of important differences in numbers.
Conclusions: This study can allow a ship's doctor to better understand the viral dynamics in case of a COVID- 19 cluster and to anticipate the exit of the crisis. Repeated tests during the active phase of the epidemic are necessary in case of a large cluster to know where to place oneself on a typical epidemic curve. Isolation and barrier measures advised by the ship's doctor remain the only weapons that can limit its magnitude.
Keywords: COVID-19; boat; infection; maritime.