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March 22, 2019

Preliminary assessment of the international spreading risk associated with the 2019 nCOV outbreak in Wuhan city

Starting in December 2019, Chinese health authorities have been closely monitoring a cluster of pneumonia cases in the city of Wuhan, in Hubei Province. It has been determined that the causing agent of the viral pneumonia among affected individuals is a new coronavirus (2019-nCoV). As of January 29, 2020, a total of 6,088 cases have been detected and confirmed in Mainland China, with more than 70 additional cases detected and confirmed internationally in Japan, Thailand, South Korea, Taiwan, Singapore, Vietnam, United States, France, Australia, Nepal, Canada, Cambodia, Sri Lanka, United Arab Emirates, Finland, and Germany. By using the cases detected outside China we are providing estimates of size of the Wuhan outbreak as of January 29th, 2020.​ By using an estimate of 10 days from exposure to detection and an effective population of 20 million people in Wuhan catchment area the estimated median size of the Wuhan outbreak is 31,200 infections [95% CI: 23,400-40,400]. Technical details are in the full report available below.

Spreading risk analysis

Here we use a detailed individual based mobility model to estimate  the risk of international dissemination. Our model simulates the mobility of people across more than 3,200 census areas in about 190 different countries. The mobility among subpopulations integrates the mobility by global air travel (obtained from the International Air Transport Association and Official Airline Guide databases) and the short-scale mobility between adjacent subpopulations. Based on the number of infected individuals detected in Wuhan (China) the model estimates two main quantities:

  • Relative importation risk: for each location Y, the platform evaluates the probability P(Y) that a single infected individual is traveling from the index areas to that specific destination Y. In other words, given the occurrence of one exported case, P(Y) is the probability that the disease carrier will appear in location Y, with respect to any other possible location.
  • Exported cases: the model estimates the probability P(n) of exporting a given number of cases n from the origin of the disease outbreak. In order to calculate the distribution P, the average time from exposure to symptoms onset/detection and inability of traveling of infected individuals must be provided.

Real time situation reports on nCov within China based on digital data streams, a Chinese online community for physicians and health care professionals, provides real-time situation reports of  the 2019 nCov oubreak in China. The information reported includes cumulative nCov case counts, outbreak maps,  and real time streaming of health authority announcements (directly or through state media) in Chinese. Link:

We closely monitor updates on as well as other publicly available data sources and extract key information in near real-time. A majority of the reports are being summarized in English with key epidemiological information on newly reported cases at the subnational level, as well as individual-level patient information on age, gender, travel history, symptom-onset and hospitalization dates. The individual level data are further processed into a line-list database for further quantitative analysis. We also keep track of research development on transmission estimates and the  natural history of nCov disease (R0, generation time)  when sufficient evidence is available.

​The team includes Vespignani’s MOBS Lab (Matteo Chinazzi, Ana Pastore y Piontti, and doctoral students, Xinyue Xiong and Jessica Davis), along with researchers from the ISI Foundation, Fred Hutchinson Cancer Research Center and the University of Florida.

This web page is routinely update as new information is available.
Last analysis considers the situation as of Jan.29, 2020.

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