From February 14 to May 31, 2020, the Okinawa prefecture confirmed 142 cases of coronavirus disease (COVID-19). Among them, 78 were the first cases of a household, with 174 household contacts. Of the 174 contacts, 21 contracted infection, indicating a secondary attack rate of 12.1% (95% confidence interval (CI) 7.6–17.9%). No significant differences were observed in the demographics and quantitative reverse transcription polymerase chain reaction (qRT-PCR) test results between first cases who became the source of infection to the household members or not. The secondary attack rates per various characteristics of the household members were significantly different: aged > 69 years (40.9% [95% CI 20.7–63.6%]) and those with underlying diseases (36.0% [95% CI 18.0–57.5%]). When the period from the onset to the isolation of the first household case was within 3 days, the secondary attack rate was low (4.5% [95% CI 0.1–22.8%]). Among the 21 secondary cases, 11 (52.4%) developed within 5 days from symptom onset in the first case within the same household. This indicates that secondary infection within the household occurred immediately after symptom onset in the first case. Thus, isolation of a suspected patient is a solution to reduce secondary household infections.

2020 年 2 月 14 日至 5 月 31 日，冲绳县确认了 142 例冠状病毒病（COVID-19）病例。其中，首例家庭病例78例，家庭接触者174人。在 174 名接触者中，21 人感染，表明二次发作率为 12.1%（95% 置信区间 (CI) 7.6-17.9%）。在成为家庭成员感染源与否的第一例病例之间，在人口统计学和定量逆转录聚合酶链反应 (qRT-PCR) 检测结果方面没有观察到显着差异。家庭成员不同特征的继发率存在显着差异：年龄> 69岁（40.9% [95% CI 20.7-63.6%]）和有基础疾病（36.0% [95% CI 18.0-57.5%]） . 从发病到隔离第一例家庭病例的时间在3天内，继发率较低（4.5% [95% CI 0.1-22.8%]）。在 21 例继发病例中，11 例（52.4%）在同一家庭内的第一例病例出现症状后 5 天内发生。这表明在第一例病例出现症状后立即发生了家庭内的继发感染。因此，隔离疑似患者是减少继发性家庭感染的解决方案。