On Mar. 25, 2020, a mobility and epidemiological study from a global consortium of researchers, led by the University of Oxford, Northeastern University and Harvard Medical School, showed that travel restrictions from and within Wuhan and Hubei from 23rd January worked to prevent the wider spread of COVID-19.

Mobile geolocation data from Baidu Inc., combined with a rich epidemiological dataset from the Open COVID-19 Data Working Group, indicated that local person-to-person transmission happened extensively early on in the coronavirus outbreak and was mitigated by drastic control measures. However, with an average incubation period of 5 days, and up to 14 days in some cases, these mobility restrictions did not begin to positively impact the data on new cases for over a week – with things appearing to get worse in the 5-7 days immediately after the lockdown as local transmission had already occurred.

Among cases reported outside Hubei, 515 cases had a known travel history to Wuhan and a symptom onset date before 31st January 2020, compared with only 39 after 31st January, illustrating the effect of travel restrictions in decreasing the spread to other Chinese provinces.