Epidemiology and Clinical Outcomes of Coronavirus Disease 2019 (COVID-19)  Patients in Northwestern China Who Had History of Exposure in Wuhan City: The Departure Time-Orginated Pinpoint Surveillance

Abstract

Background: For low-risk areas, it was vital to the management of coronavirus disease 2019 (COVID-19) patients who had history of exposure in epicenter, however, most of them could not provide the clear exposure time. So this study was designed to predict the progression of COVID-19 by using the definite departure time as original observation point.

Methods: In this retrospective study,all cases were selected from the northwest regions with the lowest population density in China to reduce the possibility of secondary exposure. As our study endpoints,we defined the incubation period as from the date of departure of Wuhan City to the date of symptom onset or the date of confirmed time(just for asymptomatic patients), the confirmed time was defined as the interval of symptom onset to the positive results (samples from the respiratory tract). Both of them were estimated by fitting a Weibull distribution on the departure date and symptom onset. The difference among the variables were analyzed.

Findings: 139 patients (98 were residents and 41 patients were travellers) were finally enrolled, about 10.1% patients (14 patients) were absent of symptom during their disease course. We estimated the median incubation period was 4.0 days (interquartile intervals, 2.0 to 8.0), the 95th percentile of the distribution was 15 days. Moreover, about 75.2% symptomatic patients had onset of symptoms within a week (94/125), however, 5.6% patients (7 patients) experienced symptoms two weeks after leaving,for one patient developed after 23.0 days. Furthermore,we explored the issue about the optimal detection time after the symptom onset,the estimation median interval from symptom onset to final diagnosis was 4.0 days (interquartile intervals,2.0 to 6.0),the 95th percentile of the distribution was 12.0 days. Further analysis showed that old patients were detected positive result later than young (5.0 days vs 4.0 days,P=0.028). Finally,the median hospitalization time was 16.0 days, ranged from 3.0 days to 45.0 days. Univariate analysis showed that age (P=0.021) and severity status (P=0.001) were correlated significantly with hospitalization time.

Interpretation: This retrospective study showed the median incubation period of COVID-19 was 4.0 days after they leaved outbreak area,the median interval from symptom onset to final diagnosis was also 4.0 days. Approximately 5.6% patients experienced symptoms two weeks after leaving Wuhan City, so the quarantine period of two weeks need to be prolonged.It was worth noting that 10.1% asymptomatic patients were detected positive results on the samples from the respiratory tract, so they should not be ignored.

Funding Statement: 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).

Declaration of Interests: 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.