岡山県における新型コロナウイルス感染症流行の疫学的特徴

Abstract

This article describes the epidemiological characteristics of coronavirus disease 2019 (COVID-19) observed in Okayama Prefecture. An epidemiological survey was performed using records from the Okayama Prefecture website and data from the newspaper Sanyo Shimbun (digital version). Infected patients were categorized into two groups: 25 patients infected during the first wave and 116 infected during the second wave. Notably, 52％ of the patients in the former group were aged ≥50 years and 66％ in the latter group were aged 20-49 years. The percentages of Okayama City residents among the infected patients were 65％ and 73％, respectively. Three clusters were identified during the second wave. The interval (mean±SD) between the polymerase chain reaction (PCR) assay results for the index case and those for the cases of secondary infection was 0.8±0.8 days (n = 6 for the cases of secondary infection) during the first wave and 2.0±1.4 days (n = 62 for the cases of secondary infection) during the second wave. As of August 24, the percentage of cumulative infected cases (7.5/100,000 patients) in Okayama Prefecture was lower than that the national level (49.3/100,000 patients). These results indicate that Okayama Prefecture has controlled the COVID-19 pandemic relatively well, primarily through the consistent implementation of public health measures, such as early case identification, careful contact tracing, and prompt PCR testing. Strict enforcement of the aforementioned measures is important to prevent or offset the effects of the third wave of COVID-19 that is expected during the influenza epidemic season.