Nowcasting and forecasting the potential domestic and international spread of the 2019-nCoV outbreak originating in Wuhan, China: a modelling study

Abstract

Background Since Dec 31, 2019, the Chinese city of Wuhan has reported an outbreak of atypical pneumonia caused by the 2019 novel coronavirus (2019-nCoV). Cases have been exported to other Chinese cities, as well as internationally, threatening to trigger a global outbreak. Here, we provide an estimate of the size of the epidemic in Wuhan on the basis of the number of cases exported from Wuhan to cities outside mainland China and forecast the extent of the domestic and global public health risks of epidemics, accounting for social and non-pharmaceutical prevention interventions.Methods We used data from Dec 31, 2019, to Jan 28, 2020, on the number of cases exported from Wuhan internationally (known days of symptom onset from Dec 25, 2019, to Jan 19, 2020) to infer the number of infections in Wuhan from Dec 1, 2019, to Jan 25, 2020. Cases exported domestically were then estimated. We forecasted the national and global spread of 2019-nCoV, accounting for the effect of the metropolitan-wide quarantine of Wuhan and surrounding cities, which began Jan 23-24, 2020. We used data on monthly flight bookings from the Official Aviation Guide and data on human mobility across more than 300 prefecture-level cities in mainland China from the Tencent database. Data on confirmed cases were obtained from the reports published by the Chinese Center for Disease Control and Prevention. Serial interval estimates were based on previous studies of severe acute respiratory syndrome coronavirus (SARS-CoV). A susceptible-exposed-infectious-recovered metapopulation model was used to simulate the epidemics across all major cities in China. The basic reproductive number was estimated using Markov Chain Monte Carlo methods and presented using the resulting posterior mean and 95% credibile interval (CrI). FindingsIn our baseline scenario, we estimated that the basic reproductive number for 2019-nCoV was 2·68 (95% CrI 2·47-2·86) and that 75 815 individuals (95% CrI 37 304-130 330) have been infected in Wuhan as of Jan 25, 2020. The epidemic doubling time was 6·4 days (95% CrI 5·8-7·1). We estimated that in the baseline scenario, Chongqing, Beijing, Shanghai, Guangzhou, and Shenzhen had imported 461 (95% CrI 227-805), 113 (57-193), 98 (49-168), 111 (56-191), and 80 (40-139) infections from Wuhan, respectively. If the transmissibility of 2019-nCoV were similar everywhere domestically and over time, we inferred that epidemics are already growing exponentially in multiple major cities of China with a lag time behind the Wuhan outbreak of about 1-2 weeks.Interpretation Given that 2019-nCoV is no longer contained within Wuhan, other major Chinese cities are probably sustaining localised outbreaks. Large cities overseas with close transport links to China could also become outbreak epicentres, unless substantial public health interventions at both the population and personal levels are implemented immediately. Independent self-sustaining outbreaks in major cities globally could become inevitable because of substantial exportation of presymptomatic case...

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease-2019 (COVID-19): The epidemic and the challenges

“…Based on observations of data from the early outbreak in mainland China from 10-24 January 2020, the trend of an increasing incidence largely follows exponential growth, and the mean basic reproduction number ( R 0 ) was estimated to range from 2.24 [95% confidence interval (CI) 1.96-2.55] to 3.58 (95% CI 2.89-4.39), associated with two-to eight-fold increases in the reporting rate [11] . Another estimation based on data from 31 December 2019 to 28 January 2020 suggested similar findings, with the R 0 for COVID-19 being 2.68 [95% credible interval (CrI) 2.47-2.86] and the epidemic doubling time being 6.4 days (95% CrI 5.8-7.1 days) [29] . The current estimate of the mean incubation period for COVID-19 is 6.4 days, ranging from 2.1 days to 11.1 days (2.5th to 97.5th percentile) [30] , with potential asymptomatic transmission.…”

Review of the 2019 novel coronavirus (SARS-CoV-2) based on current evidence

“…The estimation of R 0 varies among different research teams and is updated as more information is exposed. Wu, JT, Leung et al of York University estimated the R 0 of novel coronavirus to be 2.47-2.86 [11] using the SEIR model. Majumder of Boston Children's Hospital and his colleagues adjusted R 0 to be 2.0-3.3 using the IDEA model [12].…”

Characteristics of COVID-19 infection in Beijing

“…If not insulated for medical observation, they would not seek health care or visit hospital and cannot be found in the special period, and will spread to the other close contacts. [15][16] Therefore, to identify and control the non-pneumonia and asymptomatic cases are the important measures to prevent transmission on the COVID-19. The age of patients was from 6 months to 94-year-old, the majority of patients were young adults (77.4%), there was no significant difference between male and female in our study, population was generally susceptible.…”