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Emerg Infect Dis
. 2022 Jun 16;28(8).
doi: 10.3201/eid2808.220420. Online ahead of print.
Transmissibility of SARS-CoV-2 B.1.1.214 and Alpha Variants during 4 COVID-19 Waves, Kyoto, Japan, January 2020-June 2021
Yasufumi Matsumura, Miki Nagao, Masaki Yamamoto, Yasuhiro Tsuchido, Taro Noguchi, Koh Shinohara, Satomi Yukawa, Hiromi Inoue, Takeshi Ikeda
- PMID: 35710464
- DOI: 10.3201/eid2808.220420
Abstract
Household transmission is a primary source of SARS-CoV-2 spread. We used COVID-19 epidemiologic investigation data and viral genome analysis data collected in the city of Kyoto, Japan, during January 2020-June 2021 to evaluate the effects of different settings and viral strains on SARS-CoV-2 transmission. Epidemiologic investigations of 5,061 COVID-19 cases found that the most common category for close contact was within households (35.3%); this category also had the highest reverse transcription PCR positivity. The prevalent viral lineage shifted from B.1.1.214 in the third wave to the Alpha variant in the fourth wave. The proportion of secondary cases associated with households also increased from the third to fourth waves (27% vs. 29%). Among 564 contacts from 206 households, Alpha variant was significantly associated with household transmission (odds ratio 1.52, 95% CI 1.06-2.18) compared with B.1.1.214. Public health interventions targeting household contacts and specific variants could help control SARS-CoV-2 transmission.
Keywords: COVID-19; Japan; SARS; SARS-CoV-2; contact tracing; coronavirus; coronavirus disease; epidemiology; household contact; respiratory infections; severe acute respiratory syndrome coronavirus 2; viral genome; viruses; zoonoses.