Epidemiological characteristics of COVID-19 clusters in Hainan, China

To analyze the epidemiological characteristics of coronavirus disease 2019 (COVID-19) clusters in Hainan, and to provide a basis for the prevention and control of disease clusters. Descriptive epidemiology was used to retrospectively analyze the characteristics of disease clusters in 168 cases of COVID-19. Of the 168 COVID-19 cases, 99 (58.93%) comprised 29 clusters, 22 (75.86%) of which were imported and included 63 cases (63.64%), while 7 clusters (24.14%) were local and included 36 cases (36.36%). Of the cluster cases, 49 were men (49.49%) and 50 were women (50.50%), the median age was 52 years, and the maximum number of cases from 41 to 60 was at 37 years (37.37%). There were 67 first generation cases (67.68%), 28 (28.28%) second generation, and 4 (4.04%) third generation. Of the clusters, 68.97% occurred from January 31 to February 7, with the highest peak on February 6. The local disease clusters occurred with a time lag. The 2 cities with the most reported incidents were Sanya (10 cases, 34.48%) and Haikou (5 cases, 17.24%). Family clusters were most frequent, with 18 clusters (62.07%) involving 62 cases (62.63%), followed by social clusters, with 3 clusters (10.34%). The most complex clusters involved 3 cluster types (family, travel, and community). There was a statistically significant difference in the infectivity of the imported clusters versus the local clusters, with imported clusters being lower (Z = -2.851, P = .004). The infectivity of all cases or family members was highest in Haikou and lowest in Sanya. The infectivity of all cases with an incubation period of <= 7 days was 1.53 +/- 1.01, in which the infectivity of family members was 1.29 +/- 1.10. The infectivity of all cases with an incubation period of <= 14 days was 1.89 +/- 1.23, in which the infectivity of family members was 1.43 +/- 1.37. COVID-19 clusters in Hainan mainly occurred in families, and local clusters had high infectivity. Therefore, key populations and regions should be monitored, and targeted preventive measures should be carried out to provide a reference for the prevention and control of disease clusters.