Covid-19: Study says placing Wuhan under lockdown delayed spread by nearly 80%

China's decision to place Wuhan, the epicentre of the Covid-19 outbreak, under a lockdown in late January helped slow down the spread of the infection by nearly 80%, showed scientists in a new modelling study.

An international team of scientists studied the impact of travel restrictions on the national and international spread of the epidemic, since January 23, when China had first put Wuhan under a lockdown. The findings were published in the peer-reviewed journal - Science.

According to the study, by the time travel curbs were imposed on Wuhan, large number of people exposed to the virus had already been on the move internationally without being detected. Most Chinese cities had received many infected travellers. So, the curbs managed to delay the spread in mainland China by 3-5 days.

Initially, Shanghai (28.1%), Beijing (14%), and Shenzhen (12.8%) were the top five ranked cities as origins of international case importations.

But the scenario changed as case importations to other countries fell by around 77% when international airlines halted flights to and from China. Import of cases to other countries began to decline until mid-February, when the risk of importation of cases began rising from Japan, Thailand, South Korea, Taiwan and US, with Japan accounting for 13.9% with highest risk of importation and the US 5.7%.

The epidemic slowly grew in proportion and has now spread to over 110 countries, with death toll of over 1,000 outside mainland China. As on Wednesday, Italy remains the most affected country after mainland China with 10,000 infected cases, followed by Iran and South Korea.

Researchers have highlighted that since the outbreak has spread globally, going forward travel restrictions will have a modest impact on the spread. "The greatest benefit to mitigating the epidemic will come from behavioural changes and public health interventions - early detection, isolation and regular hand washing," said Matteo Chinazzi, lead author of the study.

According to the team, continued 90% travel restrictions to and from mainland China would only modestly affect the epidemic trajectory, unless combined with at least 50% reduction of transmission in the community.

The team had used a global disease transmission model known as Global Epidemic and Mobility Model (GLEAM) to simulate the impact of travel restrictions on the spread of Covid-19, more commonly referred to as novel coronavirus. The new strain of coronavirus has now spread to over 110 countries, with 119,541 people affected world over and global death toll at 4,292.