Effect of Public Health Intervention for COVID-19 Spread in Northwestern China: A High-Volume Research from Low Density Population Regions

Background: Public health interventions presented effectiveness in controlling coronavirus infected disease 2019(COVID-19),most studies focused on the outbreak area or the high density population regions,but the related study in low density population areas was limited. So we designed this study to research the effect of public health intervention of COVID-19 in Northwestern China with low density population. Methods: From January 21st to March 11st 2020, all patients diagnosed with novel coronavirus pneumonia(NCP) in Northwestern China with a lower population density were retrospectively reviewed.Categorical variables were summarized as numbers and percentages,the ration between the local cases(no history of leaving Northwestern China) and imported cases can represent the contagious of COVID-19 virus. Hospitalization time was assessed as well. Findings: A total of 617 COVID-19 patients were reported in Northwestern China,the morbidity and mortality were 0.000005 and 0.011, respectively,further analysis showed that the morbidity was inversely proportional to population density and distance from Wuhan City. In this study, 473 confirmed cases were enrolled to be analyzed, for these patients, 248 patients were local cases and 225 patients were imported cases, the ration between them was 1.1. When the public health interventions performed, we found that four days after Wuhan City shutdown, the number of newly increased imported patients reached to peak with 22 cases, about 76.9% of imported cases (173/225) were diagnosed within 10 days of the closure of Wuhan City. To more powerfully prevent and control the COVID-19 spread, strictly countermeasures designed and approved by local authorities were performed. Four days after implement of controlled measures, the number of imported and local patients had significantly decreased, no newly confirmed patient occurred after 19 days hard work. Moreover, asymptomatic suspicious cases underwent nucleic acid testing, about 17.3% patients(82 cases) were detected positive results, they were healthy carriers, all of them were detected during the period of quarantine or medical observation. We also found that infants or children (less than 12 years) did not belong to a disease-exempt population,15 infants or children (3.25)were diagnoses with COVID-19. Finally,the median hospitalization time was 16.0 days,rang from 2.0 days to 43.0 days, further analysis showed that the following variables were correlated significantly with hospitalization time: age(P=0.03) and severity status(P<0.001). Interpretation: Both morbidity and mortality rate of COVID-19 patients in Northwestern China were lower than that of the national average of China,it might attributed to low population density and far away from epicenter.The public health interventions,as well as the management of asymptomatic patients and children,showing significance in controlling the outbreak.The hospitalization time of patients were associated with their age and severity status. Funding Statement: We declared that we have no conflicts of interest,the opinions expressed by authors contributing to this journal do not necessarily reflect the opinions of the Centers for Disease Control and Prevention or the institutions with which the authors are affiliated. Declaration of Interests: This research was supported by grants from the Wu Jieping Medical Foundation (320.6750.17527) and Provincial Key R&D Program of Shaanxi Province(2017ZDCXL-SF-01-04-01).