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COVID-19 in Americans aboard the Diamond Princess cruise ship

Our take —

This study consisted of follow-up interviews with US citizens, residents, and non-US partners of US citizens or residents who were on board the Diamond Princess cruise ship, and genome sequencing of available specimens from US passengers. This study also leveraged PCR-RT testing results for SARS-CoV-2 conducted by Japanese health authorities and the global database of genome sequences for SARS-CoV-2 through March 20, 2020. Phylogenetic analysis showed that the SARS-CoV-2 genome sequences from study participants clustered around early genomic sequences from China, and that all genomic sequences from study participants carried a G11083T mutation which was identical to the presumed index case on the Diamond Princess. Findings from this study suggest the Diamond princess outbreak was linked to a single index case.

Study design

Cross-Sectional

Study population and setting

This study was a cross-sectional survey conducted among US citizens, residents, and non-US partners of US citizens or residents) who were passengers on the Diamond Princess cruise ship. After a passenger was diagnosed with SARS-CoV-2 on February 1, 2020, passengers and crew were quarantined on the cruise ship from February 3 to February 16, 2020. PCR-RT testing for SARS-CoV-2 was conducted by Japanese health authorities. Of 3,711 persons onboard, 437 were categorized as US passengers. These passengers were interviewed between February 28 to March 18, 2020, and the survey response rate was 229/437 (52%). Available samples from American passengers who tested positive in the United States (n=28) were used to conduct whole genome sequencing for SARS-CoV-2. This study leveraged the global database of SARS-CoV-2 genome sequences available before March 20, 2020 to build a phylogenetic tree with the samples from this study.

Summary of Main Findings

The overall attack rate for SARS-Cov-2 among US passengers and crew, 26% (114/437). Among US passengers and crew, 229 individuals responded to the survey. Of participants, 28.8% (66/229) had a SARS-CoV-2-positive RT-PCR results of which, 21% (14/66) reported no symptoms while on the cruise ship. Phylogenetic analysis showed that the SARS-CoV-2 genome sequences from study participants clustered around early genomic sequences from China. All genomic sequences from US study participants carried a G11083T mutation which was identical to the presumed index case on the Diamond Princess.

Study Strengths

While previous analyses of the Diamond Princess outbreak have been published, this study leveraged a small set of samples from study participants and the global genomic database for SARS-CoV-2 to assess the evolutionary relationships of the SARS-Cov-2 strains among US passengers and crew members of the COVID-19 outbreak on the Diamond Princess cruise ship.

Limitations

The survey response rate for study participants was low (52%) and may be subject to selection bias. Participants who responded to the study survey were more likely to be symptomatic and SARS-CoV-2 positive, which may introduce bias in the results. Notably, interviews were conducted 2-5 weeks after the quarantine and the results may be subject to recall bias. Additionally, the same size for genomic sequencing was small, and these 28 samples may not represent the other participants who tested positive for SARS-CoV-2.

Value added

This study leveraged new and existing genomic sequences among those who were on board of the Diamond Princess cruise ship to understand the evolutionary relationships of the SARS-Cov-2 strains among a small set of passengers.

This review was posted on: 9 October 2020