As the new coronavirus marches around the globe, countries with escalating outbreaks are eager to learn whether China’s extreme lockdowns were responsible for bringing the crisis there under control. Other nations are now following China’s lead and limiting movement within their borders, while dozens of countries have restricted international visitors. In mid-January, Chinese authorities introduced unprecedented measures to contain the virus, stopping movement in and out of Wuhan, the centre of the epidemic, and 15 other cities in Hubei province — home to more than 60 million people. Flights and trains were suspended, and roads were blocked. Soon after, people in many Chinese cities were told to stay at home and venture out only to get food or medical help. Some 760 million people, roughly half the country’s population, were confined to their homes, according to The New York Times. It’s now two months since the lockdowns began — some of which are still in place — and the number of new cases there is around a couple of dozen per day, down from thousands per day at the peak. “These extreme limitations on population movement have been quite successful,” says Michael Osterholm, an infectious-disease scientist at the University of Minnesota in Minneapolis. In a report released late last month, the World Health Organization (WHO) congratulated China on a “unique and unprecedented public health response [that] reversed the escalating cases”. But the crucial question is which interventions in China were the most important in driving down the spread of the virus, says Gabriel Leung, an infectious-disease researcher at the University of Hong Kong. “The countries now facing their first wave [of infections] need to know this,” he says. Nature talked to epidemiologists about whether the lockdowns really worked, if encouraging people to avoid large gatherings would have been enough and what other countries can learn from China’s experience. What happened after the lockdowns? Before the interventions, scientists estimated that each infected person passed on the coronavirus to more than two others, giving it the potential to spread rapidly. Early models of the disease’s spread, which did not factor in containment efforts, suggested that the virus, called SARS-CoV-2, would infect 40% of China’s population — some 500 million people. But between 16 and 30 January, a period that included the first 7 days of the lockdown, the number of people each infected individual gave the virus to dropped to 1.05, estimates Adam Kucharski, who models infectious-disease spread at the London School of Hygiene and Tropical Medicine. “That was amazing,” he says. The number of new daily infections in China seems to have peaked on 25 January — just two days after Wuhan was locked down. As of 16 March, roughly 81,000 cases have been reported in China, according to the WHO. Some scientists think that many cases there were unreported — either because symptoms were not severe enough for people to seek medical care, or because tests were not carried out. But it seems clear that measures implemented during this time did work, says Christopher Dye, an epidemiologist at the University of Oxford, UK. “Even if there were 20 or 40 times more cases, which seems unlikely, the control measures worked,” says Dye. Epidemiologists say China’s mammoth response had one glaring flaw: it started too late. In the initial weeks of the outbreak in December and January, Wuhan authorities were slow to report cases of the mysterious infection, which delayed measures to contain it, says Howard Markel, a public-health researcher at the University of Michigan in Ann Arbor. “The delay of China to act is probably responsible for this world event,” says Markel. A model simulation by Lai Shengjie and Andrew Tatem, emerging-disease researchers at the University of Southampton, UK, shows that if China had implemented its control measures a week earlier, it could have prevented 67% of all cases there. Implementing the measures 3 weeks earlier, from the beginning of January, would have cut the number of infections to 5% of the total. Data from other cities also show the benefits of speed. Cities that suspended public transport, closed entertainment venues and banned public gatherings before their first COVID-19 case had 37% fewer cases than cities that didn’t implement such measures, according to a preprint1 by Dye on the containment measures used in 296 Chinese cities. Multiple analyses of air travel suggest that the Hubei travel bans, which stopped people leaving the province on planes, trains or in cars, slowed the virus’ spread, but not for long2. A 6 March study3 published in Science by scientists in Italy, China and the United States found that cutting off Wuhan delayed disease spread to other cities in China by roughly four days.—Agencies
