ABSTRACT
The Diamond Princess (DP) cruise ship was put under quarantine offshore Yokohama, Japan, after a passenger who disembarked in Hong Kong was confirmed as a COVID-19 case. We performed whole genome sequencing of SARS-CoV-2 directly from PCR-positive clinical specimens and conducted a haplotype network analysis of the outbreak. All tested isolates exhibited a transversion at G11083T, suggesting that SARS-CoV-2 dissemination on the DP originated from a single introduction event before the quarantine started. Although further spreading might have been prevented by quarantine, some progeny clusters were linked to transmission through mass-gathering events in the recreational areas and direct transmission among passengers who shared cabins during the quarantine. This study demonstrates the usefulness of haplotype network analysis in identifying potential infection routes. One Sentence SummaryGenome-based tracing of SARS-CoV-2 infections among passengers and crews in Diamond Princess cruise ship during the quarantine
ABSTRACT
Seasonal influenza virus causes acute respiratory tract infections, which can be severe in children and the elderly. At present, rapid influenza diagnostic tests (RIDTs) are popular at clinical sites because they enable early diagnosis and avoid unnecessary use of antibiotics; in addition, high risk patients with underlying disease can be given antiviral drugs. However, the sensitivity and specificity of some of those tests are relatively poor. To overcome these problems, nucleic acid-based molecular point-of-care tests have been developed; however, they are significantly more expensive than RIDTs. Previously, the authors developed real-time reverse transcription loop-mediated isothermal amplification (rRT-LAMP) assays using a quenching primer to detect influenza viruses. However, the assay is limited to laboratory use because it requires a nucleic acid purification step and preparation of reaction mixtures on ice. Therefore, the authors developed and validated direct rRT-LAMP assays that require no nucleic acid purification steps using commercial RNA isolation kits, and no storage and handling of reagents on ice. These assays can be performed within 10-30 min and require only mixing a clinical specimen with extraction reagent followed by addition of a lyophilized detection reagent. The established assay showed high sensitivity and specificity when validated using 310 clinical specimens. Thus, the assay is a powerful tool for molecular diagnosis of seasonal influenza virus infection in the clinic.
