From Chain Reaction to Grid Reaction: Mobilities and Restrictions During the Epidemics of SARS and COVID-19

Epidemics are closely related to population mobility. But the COVID-19 outbreak is special in that population mobility in China 2020 is not only unprecedentedly prevalent and frequent, but has also become a basis of the global economy and many people’s livelihood. The circulation of goods and the movement of people are arguably more important than the assembly lines in factories in sustaining growth. The COVID-19 epidemic and the subsequent responses are particularly impactful because they abruptly halt what we may call a “mobility economy.”

This specific context can be discerned through a comparison to the severe acute respiratory syndrome (SARS) outbreak in 2003. Striving to contain the SARS virus, the Chinese government singled out rural-urban migrants as the priority target. At least eight urgent directives about migrants were issued by the central government and sixteen by the Beijing municipality government in April and May. In 2020, however, migrant workers have hardly been mentioned. Most measures fighting COVID-19 target the entire population. It is clear that mobility is no longer specific to migrants and has become a generalized feature across society. The meaning of mobility has changed, so has its relation to public health.

There were good reasons why the government targeted migrants in 2003. Rural-urban migrants contributed 14.81 percent of all SARS cases in the peak of the epidemic (Ministry of Health 2003). An estimated 12.6% of all migrants nationwide left cities on the wake of the outbreak (Agriculture Survey Team, National Bureau of Statistics, cited in Ma 2003) who became the main source of rural infections. In the Hebei province of Northern China, for instance, 90 percent of SARS victims were returned migrants (Asahi Shimbun 2003). A Beijing Academy of Social Sciences researcher commented that “the spread of the epidemic caused by the fleeing of migrants from Beijing due to the outbreak, and the explosive growth of SARS cases inside of Beijing caused by the concentration of migrants, for the first time bring migrants’ health issue to public attention in an extremely extraordinarily way” (Feng 2003: 10).

How exactly was the SARS epidemic related to population mobility? My fieldwork at that time suggests that, different from narratives in public media and policy documents, few migrants left city because of health concerns. Migrants were much less sensitive to the epidemic threat than their urban middleclass counterparts. Migrants’ mobility was a result of a chain reaction. In late April, after a two months-long cover up, the Chinese government suddenly acknowledged the epidemic as a national emergency under strong pressure from the international community and domestic urban residents. Public entertainment venues and construction sites were considered high-risk areas and were shut down overnight. Beijing closed about 70 percent of all restaurants in May (Yang 2003), which could put up to 237,300 migrants out of job (my estimate based on Xinhua News Agency 2003). Jobless, migrants had to go home. They became the worst victims of the virus, of economic disruption and of social stigma. “Chain reaction” means that the connection between epidemic and migration was mediated by social stratification (Xiang 2003).

In comparison, the COVID-19 epidemic has triggered “grid reactions.” Residential communities, districts, cities and even entire provinces act as grids to impose blanket surveillance over all residents, minimize mobilities, and isolate themselves. In the Chinese administrative system, a grid is a cluster of households, ranging from 50 in the countryside to 1000 in cities. Grid managers (normally volunteers) and grid heads (cadres who receive state salaries) make sure that rubbish is collected on time, cars are parked properly, and no political demonstration is possible. During an outbreak, grid managers visit door to door to check everyone’s temperature, hand out passes which allow one person per household to leave home twice a week, and in the case of collective quarantine, deliver food to the doorstep of all families three times a day.

Grid reaction, just like the COVID-19 virus, is highly contagious. Once the central government declared the war on the virus, localities across the nation adopted strict measures, even in remote places with no reported infection. In no time the entire nation put itself under gridlock. Grid reaction is not about community grids only; it refers to the all-out, undifferentiated, war-like strategy. Turning entire hospitals into COVID-19 wards and building barricades around villages are part of the grid reaction too.

Total (im)mobilization is regarded necessary partly because of the unprecedented mobility level in China. Over 3.6 billion Chinese travelled by train and 660 million by air in 2019, compared to 0.95 billion and 87 million respectively in 2003; the number of private motor vehicles increased from 13 million in 2003 to 206 million (CEIC Data 2020). Mobility has increased also because work is casualized. Between 2008 and 2016, the informal sector generated 10 million jobs a year, while stable employment in state-owned enterprises and foreign-owned enterprises increased much more slowly and in fact shrank by nearly 2 million between 2015 and 2016 (Qian 2020: 2). The “labor dispatch” service is legalized in 2008, which by 2011 accounted for 13.1% of all the jobs nationwide (National Federation of Trade Unions 2012: 35). Dispatch agencies move workers from one project site to another. Many more rural-urban migrants are now moving between places and between jobs. This also means that the government can no longer rely on employers as a mediator in monitoring employees. Feasible measures have to target the population in entirety.

Grid reaction can be deeply disruptive. Firstly, just like chain reaction, grid reaction induced unintended movements that may further spread the virus. The Wuhan lockdown triggered flights from the city, which is said to have turned Wenzhou into an epicentre outside of Hubei (Yao 2020). Inside Hubei, the shortage of medical resources in relation to the concentrated infection due to the lockdown compelled patients to move from hospital to hospital seeking care, often on foot because of the suspension of transport. As grids are based on physical boundaries, grid reaction has also fuelled alarming place-based stigma. Persons originally from infected places, regardless how long they had been away, were locked in at home by neighbours, and were even attacked online. Reports also show rising conflicts between residents and officials due to forced quarantine.[1]

Disruptions in economy are the most obvious. As China’s 2020 economy is four times that of its 2003 size, and more importantly, as it plays an increasingly central role in global supply chains, any glitch in circulation has far-reaching consequences. But it must be emphasized that those who rely on mobility for their livelihood may suffer the most. Taxi drivers, delivery workers, staff in the logistics and service sectors cannot work without moving, and will have no customers without others on the move. Many of them live on daily wages. Two months’ standing still could be devastating.

Thus a Catch-22 scenario: prevalent mobility leaves the government with few options other than grid reaction, but it at the same time renders such response unbearably disruptive. When the Chinese society becomes more mobile, responses to risks appear more crude and clumsy. How can a mobility economy be organized in a more sustainable and equitable matter? This is a fundamental challenge for researchers and policy makers in coming decades.


[1] Based on numerous reports across official media outlets, particularly Zhongguo Xinwen Zhoukan (China News Weekly), Sanlian Shenhou Zhoukan (Sanlian Life Weekly), Nanfang Zhoumo (South China Weekend), and Renwu (People). archives reportages related to the COVID-19 outbreak.

Works Cited

Asahi Shimbun. 2003. “SARS outbreak in Hebei”, 17 June. Page missing. CEIC Data. 2020. “China: Transport and Telecommunication”, accessed on 25 February 2020.

Feng Xiaoying. 2003. Feidian yu liudong renkou guanli moshi gaige lujing de xuanze (SARS and the Choice of Reform Paths for Migrant Population Management Model). Chengshi Wenti (Urban Issues). 4 (114): 9-12.

Ma Xiaohe. 2003. Jiji caiqu youxiao cuoshi fangzhi feidian zaocheng nongmin shouru xiahua (Take Proactive Measures to Prevent Farmers’ Income Loss). In Research Report Series of Macro Economic Research Academy, Economic Development Committee of China, 9 June. Available at jsp?subframeid=1, accessed on 6 January 2004.

Ministry of Health, China. “Quezhen binli an zhiye fenbu” (Distribution of confirmed cases by occupation). In Chuanranxing Feidianxing Feiyan Yiqing Dili Xinxi Xitong (Geographic Information System on Infectious Atypical Pneumonia). Available at http: sarsmap, accessed on 16 July 2003.

National Federation of Trade Unions Research Team on Labor Dispatch, 2012, Dangqian woguo laowu paiqian yonggong dizwei diaocha. [A survey on the current employment status of labor dispatch in China], Zhongguo Laodong [China Labor], No. 5: 23.

Qian Jiwei. 2020. Under-coverage of Social Insurance in China’s Informal Economy. No. 9. EAI Commentary.

Xiang, Biao. 2003. SARS and Migrant Workers in China. Asian and Pacific Migration Journal.  12 (4): 467-499.

Xinhua News Agency. 2003. “Diaocha xianshi: zhonggou yin feidian fanxiang nongming bacheng reng zai dengdai guangwang” (Survey shows 80 per cent of returned migrants due to Atypical Pneumonia still wait and see), 19 June.

Yang Bin. 2003. Feidian kenan daozhi Beijing canyinye 5000 jia chuju (Atypical Pneumonia may force 5,000 restaurants out of business), Sinanews, 4 June.

Yao, Gaoyuan (Mayor of Wenzhou), Zhejiang province, Interview at China Central TV News 1 + 1 column, 2 February 2020. Available on

Biao Xiang is a Professor of Social Anthropology at the University of Oxford, specializing in migration and social changes in Asia. He is the author of Making Money from Making Order (forthcoming); Global “Body Shopping”; Transcending Boundaries; Return: Nationalizing Transnational Mobility in Asia (lead editor) and numerous articles in both English and Chinese. A number of articles have been translated into Japanese, French, Korean, Spanish and Italian.

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