Spatial pattern of severe acute respiratory syndrome in-out flow in 2003 in Mainland China.

Chengdong Xu,Li Wang,Chunxiang Cao,Jinfeng Wang

doi:10.1186/s12879-014-0721-y

Abstract

BackgroundSevere acute respiratory syndrome (SARS) spread to 32 countries and regions within a few months in 2003. There were 5327 SARS cases from November 2002 to May 2003 in Mainland China, which involved 29 provinces, resulted in 349 deaths, and directly caused economic losses of $18.3 billion.MethodsThis study used an in-out flow model and flow mapping to visualize and explore the spatial pattern of SARS transmission in different regions. In-out flow is measured by the in-out degree and clustering coefficient of SARS. Flow mapping is an exploratory method of spatial visualization for interaction data.ResultsThe findings were as follows. (1) SARS in-out flow had a clear hierarchy. It formed two main centers, Guangdong in South China and Beijing in North China, and two secondary centers, Shanxi and Inner Mongolia, both connected to Beijing. (2) “Spring Festival travel” strengthened external flow, but “SARS panic effect” played a more significant role and pushed the external flow to the peak. (3) External flow and its three typical kinds showed obvious spatial heterogeneity, such as self-spreading flow (spatial displacement of SARS cases only within the province or municipality of onset and medical locations); hospitalized flow (spatial displacement of SARS cases that had been seen by a hospital doctor); and migrant flow (spatial displacement of SARS cases among migrant workers). (4) Internal and external flow tended to occur in younger groups, and occupational differentiation was particularly evident. Low-income groups of male migrants aged 19–35 years were the main routes of external flow.ConclusionsDuring 2002–2003, SARS in-out flow played an important role in countrywide transmission of the disease in Mainland China. The flow had obvious spatial heterogeneity, which was influenced by migrants’ behavior characteristics. In addition, the Chinese holiday effect led to irregular spread of SARS, but the panic effect was more apparent in the middle and late stages of the epidemic. These findings constitute valuable input to prevent and control future serious infectious diseases like SARS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0721-y) contains supplementary material, which is available to authorized users.

Highlights

Severe acute respiratory syndrome (SARS) spread to 32 countries and regions within a few months in 2003
(3) External flow and its three typical kinds showed obvious spatial heterogeneity, such as self-spreading flow; hospitalized flow; and migrant flow
The Chinese holiday effect led to irregular spread of SARS, but the panic effect was more apparent in the middle and late stages of the epidemic

Summary

Introduction

Severe acute respiratory syndrome (SARS) spread to 32 countries and regions within a few months in 2003. Humans have been exposed continually to newly emerged infectious diseases [1,2,3], especially 1918 influenza, 2003 severe acute respiratory syndrome (SARS), 2009 H1N1 influenza, 2012 novel coronavirus, 2013 H7N9 influenza pandemics and Ebola virus in 2014. Without exception, these viruses were harbored in an animal reservoir and jumped the species barrier to infect humans, presenting a serious threat to human health. Wang et al used the SIR or SEIR model to study SARS transmission in Beijing, Hong Kong or Singapore Their results showed that public health interventions such as early recognition, prompt isolation, and appropriate precautionary measures, could effectively limit spread of the virus. These studies were good at reflecting the spatial diffusion of SARS in the local area, but not at an interprovincial level

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