Lessons from a Covid-19 outbreak on a naval aircraft carrier

1. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was shown to spread rapidly amongst the U.S.S Theodore Roosevelt crew due to close close-quarter conditions and asymptomatic infected crew members.

2. The Navy implemented procedures prior to deployment such as 14-day quarantine and viral testing for all members to reduce the risk of SARS-CoV-2 asymptomatic carriers on board.

Evidence Rating Level: 2 (Good)

Study Rundown: An outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection occurred on the U.S.S. Theodore Roosevelt, while conducting operations in the western Pacific Ocean. Upon outbreak identification, the ship was diverted to a 42-bed base hospital at the U.S. Naval Base Guam. The report detailed the findings from the U.S. Navy response and epidemiological investigation during the outbreak. Each crew member was evaluated, tested, placed into isolation or quarantine, and monitored daily during the outbreak. The study determined the infection spread was accelerated by the close-quarter conditions and the presence of asymptomatic infected crew members. Furthermore, the report outlined procedural changes to mitigate the infection spread through mandatory quarantine and universal testing of crew members. This retrospective cohort study was limited by the study population. The majority of the crew was less than 30 years of age and no member was older than 64 years of age. Therefore, the prognosis for the infection amongst the crew was not representative of the general population. Nonetheless, the report outlined the importance of a coordinated response from multiple agencies and guideline compliance to effectively reduce SARS-CoV-2 transmission.

Click to read the study in NEJM

Relevant Reading: Estimation of the reproductive number of novel coronavirus (COVID-19) and the probable outbreak size on the Diamond Princess cruise ship: a data-driven analysis

In-Depth [retrospective cohort]: This retrospective cohort study reported the naval response and epidemiological investigation of the SARS-CoV-2 outbreak on the U.S.S Theodore Roosevelt between March 23 and May 18, 2020. Thirteen days into operations, three crew members presented to the medical department with symptoms suggestive of coronavirus 2019 (Covid-19). After positive confirmatory testing by real-time reverse-transcriptase polymerase chain reaction (rRT-PCR), the ship was diverted to Naval Base Guam where confirmed Covid-19 members were placed in isolation at the base. Furthermore, members with negative Covid-19 tests and no symptoms were also quarantined. All crew members underwent Covid-19 screening and rRT-PCR testing. Overall, 1271 crew members (26.6% of the crew) tested positive for SARS-CoV-2 through the laboratory-confirmed Covid-19 test. Within this group, 572 (43.0%) remained asymptomatic, 293 (22.0%) were symptomatic, and 406 (30.5%) were presymtomatic at the time of their positive test. 978 of the 1271 crew members (76.9%) were not symptomatic at the time of their positive test. The predominant symptoms at illness onset were cough (32.8%), headache (31.0%), and altered sense of taste or smell (24.1%). The most common symptoms at any point during the illness were headache (68.0%), cough (59.5%), and nasal or sinus congestion (43.8%). Workplaces in tighter spaces such as the reactor, engineering, supply, and weapons department appeared more likely to have confirmed or suspected cases compared to open-air conditions such as the air and duck crew. After the outbreak, the Navy implemented procedures to mitigate the risk of deploying with asymptomatic carriers of SARS-CoV-2 on board by isolating new crew members from community exposure for 14 days. Naval ships reduced shore leaves at foreign ports to prevent the crew from bringing the virus on board. Finally, implementation of preventive measures such as mask use, social distancing, and strict hand hygiene all have resulted in the deployment of several ships without another serious outbreak. Taken together, the SARS-CoV-2 outbreak on the U.S.S Theodore Roosevelt was attributed to the presence of asymptomatic carriers and close-quarter conditions. However, proper public health measures and adequate testing resulted in reducing future outbreak on naval ships.

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