{'fraction_non_alphanumeric': 0.03275894716909676, 'fraction_numerical': 0.03313766332134065, 'mean_word_length': 4.722643553629469, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Correlation between travellers departing from Wuhan before the Spring Festival and subsequent spread of COVID-19 to all provinces in China.

We found a strong correlation between travel volumes departing from Wuhan, Hubei Province before the Spring Festival and the extent of amplification of the outbreak of COVID-19 in China in 2020, with 100 top cities. Almost 70% of exportations were within cities in Hubei province.


Highlight:
We found a strong correlation between travel volumes departing from Wuhan, Hubei Province before the Spring Festival and the extent of amplification of the outbreak of COVID-19 in China in 2020, with 100 top cities. Almost 70% of exportations were within cities in Hubei province.
Keywords Coronavirus; Public health emergency of international concern; 2019-nCov; Migration; Containment; Quarantine; Travel In December 2019, a cluster of pneumonia, now known as COVID-19, was reported in Wuhan, Hubei Province, in the central part of China. As of 9 March 2020, more than 80,700 COVID-19 cases have been reported in China. Wuhan was the epicentre. Wuhan is the capital city of Hubei Province, and is one of the well-developed cities in China.
Wuhan is also a major transportation hub in China, as it is located on the crossroads between the railway line linking Beijing and Guangzhou and the Yangtze River linking Chongqing and Shanghai. In response to the rapid spread within Hubei Province and exportations to other countries 1 , the Chinese government implemented a lock-down of Wuhan on 24 January, 2020, the day before Spring Festival. Population movement is high during Spring Festival with about 2.97 billion passengers travelling during the Spring Festival in 2019. 2 As Wuhan is a major transportation hub in China, it is estimated that about five million people left the city during the Spring Festival travel rush before Jan 24, 2020. The aim of this essay is to explore the correlation between travellers departing from Wuhan before the Spring Festival and the extent of amplification of the outbreak of COVID-19 in China.
The data referring to population mobility were collected from the Baidu Migration database (http://qianxi.baidu.com/), which is a non-profit project aimed to provide data on population mobility during the Chinese Spring Festival rush. The database is able to provide the overall proportion of travellers departing from one city during a certain period. According to the instructions of the database, the proportion of travellers departing from Wuhan to one city is calculated by n1/n2, where n1 is defined as the number of travellers departing from Wuhan to one selected city during a certain period and n2 is the total number of travellers departing from Wuhan during a certain period.
For instance, the proportion of travellers departing from Wuhan to Beijing was 1%, if the number of travellers departing from Wuhan to Beijing was 50, 000 during a certain period and the total number of travellers departing from Wuhan was 5 million during the same period. We extracted data between Jan 10, 2020 and Jan 24, 2020, on travellers departing from Wuhan to other cities and calculated the proportions of travellers departing from Wuhan to the top 100 cities in China.
All confirmed cases of COVID-19 and persons recovered from COVID-19 in the top 100 cities were aggregated from official announcements by searching the publicly available sources. The deadline was at 11:59 p.m. Feb 11, 2020 (China standard time, CST).
According to the official announcements, all cases were applied with the same diagnostic criteria based on the recommendation by the National Health Commission of China (http://www.nhc.gov.cn/). No ethical approval was needed for this study. The proportion of cases in a destination city was calculated by m1/m2, where m1 is the number of confirmed cases found in one selected city and m2 is that found in China outside of Wuhan. The recovery rate in each city was also recorded. Furthermore, considering several socioeconomic factors had a potential impact in the spreading of COVID-19, population, population density, regional income, and level of health care in the top 100 cities were extracted from the National Bureau of Statistics of China

Correlation between the proportion of travellers departing from Wuhan and four potential risk factors in the top 100 cities
We did not find a correlation between number of cases and the population density (P = 0.643), regional income (P = 0.617), or level of health care (P = 0.244). Meanwhile, there were no correlations between recovery rate and the population (P = 0.926), population density (P = 0.680), regional income (P = 0.073), or level of health care (P = 0.063).
There was a strong positive correlation between the proportion of travellers departing from Wuhan and the number of cases (Spearman's r = 0.773, P = 0.000, Fig. 2A

Conclusions
The main destination cities of travellers departing from Wuhan before the Spring  The areas with a high proportion of travellers departing from Wuhan (blue) also companied with a high proportion of COVID-19 cases (red) (Fig. 1A). The travellers departing from Wuhan before the Spring Festival (Jan 25) were far more than those after the Spring Festival in 2020 (yellow) and 2019 (white) (Fig.1B).