Clusters of COVID‐19 in long‐term care hospitals and facilities – Japan, Jan 15‐May 9, 2020

Iritani, Osamu; Okuno, Tazuo; Hama, Daisuke; Kane, Asami; Kodera, Kumie; Morigaki, Kozue; Terai, Toshio; Maeno, Norie; Morimoto, Shigeto

AIM: To clarify the association of cluster number and size of coronavirus disease 2019 (COVID‐19) in long‐term care (LTC) hospitals/facilities, general medical/welfare facilities, and non‐medical/welfare facilities, with morbidity and mortality in 47 prefectures during Jan 15 ‐ May 9, 2020 in Japan. METHODS: Information on COVID‐19 clusters (n >2) and morbidity and mortality of COVID‐19 was collected. RESULTS: A total of 381 clusters with 3,786 infected cases were collected, accounting for 23.9% of 15,852 cumulated cases on May 9, 2020. Although the cluster number (/10(7) subjects) in LTC hospitals/facilities was significantly smaller compared to those in the other two groups, the cluster size in LTC hospitals/facilities was significantly larger than that in non‐medical/welfare facilities. Cluster numbers in general medical/welfare facilities and in non‐medical/welfare facilities were significantly positively correlated with morbidity (/10(5)), indicating relatively early identification of clusters in these facilities. Unlike in these facilities, cluster size in LTC hospitals/facilities was significantly positively correlated with morbidity, indicating that clusters in LCT hospitals/facilities were finally identified after already having grown to a large size in areas where infection was prevalent. Multivariate logistic regression analysis revealed that both cluster number and cluster size only in LTC hospitals/facilities were independently associated with higher mortality (> median: 0.64/10(5) subjects) after adjustment. CONCLUSIONS: Preventive efforts against COVID‐19 outbreaks even at the early phase of the epidemic are critically important in LTC hospitals/facilities, since both larger number and size of cluster only in LTC hospitals/facilities were independently linked to higher mortality in prefectures in Japan. <248 words>