Global Health & Medicine 2022;4(3):192-196.

A low proportion of asymptomatic COVID-19 patients with the Delta variant infection by viral transmission through household contact at the time of confirmation in Ibaraki, Japan

Ogata T, Tanaka T, Irie F, Nozawa Y, Noguchi E, Seo K, Tanaka E

Abstract

We conducted a study to investigate the proportion of patients with asymptomatic coronavirus disease 2019 (COVID-19) infected with the Delta variant compared with those infected with the wild-type strain at the time of confirmation. A total of 504 patients with confirmed severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2) infection by viral transmission through household contact in Ibaraki, Japan were included. The proportion of asymptomatic COVID-19 patients at the time of confirmation was compared between patients infected with L452R mutation strain from June to September 2021 and those infected with the wild-type strain from November 2020 to January 2021, and was found to be 14.2% and 28.8%, respectively (relative risk, 0.49; 95% confidence interval, 0.35-0.70). The proportion of asymptomatic COVID-19 patients by viral transmission through household contact was lower among the Delta variant than those among the wild-type strain at the time of confirmation. It might contribute to attenuation of transmission.

KEYWORDS: Delta variant, coronavirus disease 2019 (COVID-19), asymptomatic, Japan

DOI: 10.35772/ghm.2021.01116

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