Impacts of social and economic factors on the transmission of coronavirus disease (COVID-19) in China

Yun Qiu; Xi Chen; Wei Shi

As a robustness test, Table 5 reports the estimation results if the analysis sample does not include cities in Hubei province. Column (4) of Table 5 indicates that in the first half sample, one new case leads to 1.517 more cases within a week, and this becomes small and statistically not significant in the second half sample. Besides, in the second half sample, one new case decreases new infections by 0.724 between 1 and 2 weeks, which is larger than the estimate (0.438) with cities in Hubei province included. Overall, the spread of the virus has been effectively contained between For the between-city transmission from Wuhan, we observe that the population flow better explains the contagion effect than geographic proximity (Table 4 ). In the first half sample, one new case in Wuhan leads to more cases in other cities which receive more population flows from Wuhan within one week. In the second half sample, more arrivals from Wuhan one week earlier can still be a risk. A back of the envelope calculation indicates that one new case in Wuhan leads to 0.067 (0.120) more cases in the destination city per 10,000 travelers from Wuhan within one (two) week between January 19 and February 1 (February 2 and February 15) 13 . Note that while the effect is statistically significant, it should be interpreted in context. It was estimated that 15, 000, 000 people would travel out of Wuhan during the Lunar New Year holiday 14 . If all had gone to one city, this would have directly generated about 280.5 cases within two weeks. The risk of infection is likely very low for most travelers except for few who have previous contacts with sources of 13 It is estimated that 14,925,000 people traveled out of Wuhan in 2019 during the Lunar New Year holiday (http: //www.whtv.com.cn/p/17571.html). The sum of Baidu's migration index for population flow out of Wuhan during the 40 days around the 2019 Lunar New Year is 203.3, which means one index unit represents 0.000013621 travelers. The destination share is in percentage. With one more case in Wuhan, the effect on a city receiving 10,000 travelers from Wuhan is 0.00490 × 0.000013621 × 100 × 10000 = 0.067. 14 http://www.whtv.com.cn/p/17571.html infection, and person-specific history of past contacts may be an essential predictor for infection risk, in addition to the total number of population flows 15 .