About five million people were able to flee Wuhan before the city was put under quarantine because of the coronavirus, taking the deadly infection with them to neighbouring areas.
For weeks after the first reports of a mysterious new virus in Wuhan, millions of people poured out of the central Chinese city, cramming onto buses, trains and planes as the first wave of China’s great Lunar New Year migration broke across the nation.
Some carried with them the new virus that has since claimed over 800 lives and sickened more than 37,000 people.
Officials finally began to seal the borders on January 23, but it was too late.
Speaking to reporters a few days after the city was put under quarantine, the mayor estimated that 5 million people had already left.
Now, an analysis of domestic travel patterns using map location data from Chinese tech giant Baidu shows that in the two weeks before Wuhan’s lockdown, nearly 70% of trips out of the central Chinese city were within Hubei province.
The travel patterns broadly track with the early spread of the virus.
The cities outside Hubei province that were top destinations for trips from Wuhan between January 10 and January 24 were Chongqing, a municipality next to Hubei province, Beijing and Shanghai.
The majority of confirmed cases and deaths have occurred in China, within Hubei province, followed by high numbers of cases in central China, with pockets of infections in Chongqing, Shanghai and Beijing as well.
‘It´s definitely too late,’ said Jin Dong-Yan, a molecular virologist at Hong Kong University´s School of Biomedical Sciences. ‘Five million out. That’s a big challenge. Many of them may not come back to Wuhan but hang around somewhere else.
‘To control this outbreak, we have to deal with this. On one hand, we need to identify them. On the other hand, we need to address the issue of stigma and discrimination.’
He added that the initial spread of travellers to provinces in central China with large pools of migrant workers and relatively weaker health care systems ‘puts a big burden on the hospitals … of these resource-limited provinces.’
It’s important to understand the population movements out of Wuhan before the city’s lockdown, said Lai Shengjie, a WorldPop researcher who used to work at Chinas Center for Disease Control and Prevention.
‘Maybe they hadn’t developed symptoms but could transmit the virus. We need to look at destinations across China and the world and focus on the main destinations and try to prepare for disease control and prevention,’ he said.
The last trains left Wuhan the morning of January 23, cutting off a surge of outbound travel that had begun three days earlier, Baidu data shows.
From January 23 to January 26, the 15 cities that Baidu data shows received the most travellers from Wuhan – a combined 70% – all imposed some level of travel restrictions.
Other nations soon followed suit, including the United States, Australia, Singapore, New Zealand and the Philippines, all of which have sharply restricted entry for people coming from China.
Others, like Italy and Indonesia, have barred flights.
The top 10 global destinations for travellers from high-risk Chinese cities around Lunar New Year, according to their analysis, were Thailand, Japan, Hong Kong, Taiwan, South Korea, the United States, Malaysia, Singapore, Vietnam and Australia.
In Africa, Egypt, South Africa, Ethiopia, Mauritius, Morocco, Nigeria and Kenya topped the list.
The African continent is particularly vulnerable because of the weaker health infrastructure in many countries, and the longer cases go undetected, the more likely they are to spread.
‘Capacity is quite weak in many African health services,’ Dr. Michel Yao, emergency operations manager for the World Health Organization in Africa, told the AP. This new virus ‘could overwhelm health systems we have in Africa.’
The Africa Centers for Disease Control formed three years ago in response to the Ebola crisis in West Africa, said screening has been stepped up at ports of entry across Africa.
Egypt began screening passengers from affected areas in China on Jan. 16. Over the next eight days, Nigeria, Ethiopia, South Africa, Mauritius and Kenya all put screening systems in place. No confirmed cases have been reported.
The first case of the virus outside China was reported on January 13 in Thailand, followed two days later by Japan, the countries with the highest connectivity risk, according to WorldPop’s analysis.
Within 10 days of Wuhan’s quarantine, the virus had spread to more than two dozen countries; nine of the 10 countries with the most flight connections to at-risk mainland cities also had the highest numbers of confirmed cases, mostly afflicting people who had been in China.