Infection rate among close contacts of patients with coronavirus disease in Japan: a descriptive study and literature review
Article Category: Original article
Online veröffentlicht: 09. Okt. 2023
Seitenbereich: 115 - 123
DOI: https://doi.org/10.2478/abm-2023-0051
Schlüsselwörter
© 2023 Osamu Yamamura et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.
Background
In Japan, on April 20, 2020, the definition of a close contact regarding coronavirus disease (COVID-19) was changed from a long-term contact time to a specified contact time of 15 min and from a contact distance of 2 m to 1 m.
Objectives
We aimed to determine the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rate among close contacts of patients with COVID-19 and determine the impact of the infection on transmission among close contacts.
Methods
The numbers of SARS-CoV-2 tests, SARS-CoV-2-positive cases, and close contacts of patients with COVID-19 were assessed between March 2020 and February 2021 in Fukui Prefecture, Japan. The study period was subdivided into 3 periods. The second and third period contained data with the changed definition of close contact.
Results
Overall, 32,238 SARS-CoV-2 tests were performed. There were 545 patients with COVID-19 and 1487 close contacts, of whom 267 tested positive. The highest infection rate occurred in period 3. Distance, protective measures, and contact time with COVID-19 patients influenced the increased infection rate. The infection rate showed a rising trend from 11.1% in period 1 to 19.2% and 20.0% in periods 2 and 3, respectively (Cochran–Armitage test;
Conclusions
Female sex is a risk factor for transmission by close contacts. The rate of infection among close contacts may be associated with contact time, contact distance, and protective measures.