China has flooded cities and villages with battalions of neighbourhood busybodies, uniformed volunteers and Communist Party representatives to carry out one of the biggest social control campaigns in history.

The goal: to keep hundreds of millions of people away from everyone but their closest kin.

The nation is battling the coronavirus outbreak with a grassroots mobilisation reminiscent of Mao-style mass crusades not seen in China in decades, essentially entrusting front line epidemic prevention to a supercharged version of a neighbourhood watch.

Housing complexes in some cities have issued the equivalents of paper hall passes to regulate how often residents leave their homes. Apartment buildings have turned away their own tenants if they have come from out of town. Train stations block people from entering cities if they cannot prove they live or work there. In the countryside, villages have been gated off with vehicles, tents and other improvised barriers.

Despite China’s arsenal of high-tech surveillance tools, the controls are mainly enforced by hundreds of thousands of workers and volunteers, who check residents’ temperature, log their movements, oversee quarantines and — most important — keep away outsiders who might carry the virus.

Residential lockdowns of varying strictness — from checkpoints at building entrances to hard limits on going outdoors — now cover at least 760 million people in China, or more than half the country’s population, according to a New York Times analysis of government announcements in provinces and major cities. Many of these people live far from the city of Wuhan, where the virus was first reported and which the government sealed off last month.

Throughout China, neighbourhoods and localities have issued their own rules about residents’ comings and goings, which means the total number of affected people may be even higher. Policies vary widely, leaving some places in a virtual freeze and others with few strictures.

China’s top leader, Xi Jinping, has called for an all-out “people’s war” to tame the outbreak. But the restrictions have prevented workers from returning to factories and businesses, straining China’s giant economy. And with local officials exercising such direct authority over people’s movements, it is no surprise that some have taken enforcement to extremes.

Li Jing, 40, an associate professor of sociology at Zhejiang University in the eastern city of Hangzhou, was almost barred from taking her husband to a hospital recently after he choked on a fish bone during dinner. The reason? Her neighbourhood allows only one person per family to leave the house, every other day.

“Once the epidemic was disclosed, the central government put huge pressure on local officials,” Professor Li said. “That triggered competition between regions, and local governments turned from overly conservative to radical.”

“Even when the situation is relieved or if the mortality rate turns out not to be high, the government machine is unable to change direction or tune down,” she added.

China’s prevention efforts are being led by its myriad neighbourhood committees, which typically serve as a go-between for residents and the local authorities. Supporting them is the government’s “grid management” system, which divides the country into tiny sections and assigns people to watch over each, ensuring a tight grip over a large population.

Zhejiang province, on China’s southeastern seaboard, has a population of nearly 60 million and has enlisted 330,000 “grid workers”. Hubei province, whose capital is Wuhan, has deployed 170,000. The southern province of Guangdong has called upon 177,000, landlocked Sichuan has 308,000 and the megacity of Chongqing has 118,000.

The authorities are also combining enormous manpower with mobile technology to track people who may have been exposed to the virus. China’s State-run cellular providers allow subscribers to send text messages to a hotline that generates a list of provinces they have recently visited.

At a high-speed rail station in the eastern city of Yiwu last week, workers in hazmat suits demanded that passengers send the text messages that show their location data before being allowed to leave.

An app developed by a State-run maker of military electronics lets Chinese citizens enter their name and national ID number and be told whether they may have come in contact, on a plane, train or bus, with a carrier of the virus.

It is too early to say whether China’s strategy has contained the outbreak. With large numbers of new infections being reported every day, the government has clear reasons for minimising human contact and domestic travel. But experts say that in epidemics, overbearing measures can backfire, scaring infected people into hiding and making the outbreak harder to control.