A comparative study of international and Chinese public health emergency management from the perspective of knowledge domains mapping

Background At the end of 2019, the outbreak of coronavirus disease 2019 (COVID-19) severely damaged and endangered people’s lives. The public health emergency management system in China has played an essential role in handling the response to the outbreak, which has been appreciated by the World Health Organization and some countries. Hence, it is necessary to conduct an overall analysis of the development of the health emergency management system in China. This can provide a reference for scholars to aid in understanding the current situation and to reveal new research topics. Methods We collected 2247 international articles from the Web of Science database and 959 Chinese articles from the China National Knowledge Infrastructure database. Bibliometric and mapping knowledge domain analysis methods were used in this study for temporal distribution analysis, cooperation network analysis, and co-word network analysis. Results The first international article in this field was published in 1991, while the first Chinese article was published in 2005. The research institutions producing these studies mainly existed in universities and health organizations. Developed countries and European countries published the most articles overall, while eastern China published the most articles within China. There were 52 burst words for international articles published from 1999–2018 and 18 burst words for Chinese articles published from 2003–2018. International top-ranked articles according to the number of citations appeared in 2005, 2007, 2009, 2014, 2015, and 2016, while the corresponding Chinese articles appeared in 2003, 2004, 2009, and 2011. Conclusions There are differences in the regional and economic distribution of international and Chinese cooperation networks. International research is often related to timely issues mainly by focusing on emergency preparedness and monitoring of public health events, while China has focused on public health emergencies and their disposition. International research began on terrorism and bioterrorism, followed by disaster planning and emergency preparedness, epidemics, and infectious diseases. China considered severe acute respiratory syndrome as the starting research background and the legal system construction as the research starting point, which was followed by the mechanism, structure, system, and training abroad for public health emergency management.


Background
Public health emergencies have increased in recent years and have shown a trend of causing considerable damage [1]. According to the emergency events database (EM-DAT), the most widely used and influential disaster database in the world, the average number of deaths per major public health event was more than 10,000 [2]. Population growth, urban development, migration, and other issues brought about by globalization have sped up the incidence of public health events, such as epidemics [3,4]. Public health events also propelled the process of emergency management, giving top priority to changes in emergency operations. The outbreak of coronavirus disease 2019  in China spread rapidly throughout the world in a short time, which illustrated the need to build a resilient health emergency system that can withstand epidemics [5].
Public health emergency management (PHEM) is a relatively new field that draws on specific sets of knowledge, techniques, and organizing principles found in emergency management [6]. Specifically, it includes public health emergency planning, organization, leadership, coordination, control, evaluation, prevention, preparation, and response [7]. For COVID-19, China's PHEM system quickly took the following measures: emergency mobilization measures within the government, lockdown of cities and communities, nationwide medical mobilization, provision of financial support, preferential policies for the medical community and pharmaceutical industry, and the categorical comprehensive publicity to spread prevention and treatment knowledge [8]. These measures effectively reduced the spread of the disease. Thus, current recommendations are mostly derived from the reported Chinese experience [9]. Given the weaknesses and deficiencies exposed by the COVID-19 outbreak, people have recognized the need to improve the national PHEM system [10,11].
A growing body of research has studied PHEM from different perspectives, mainly those of institutions, funds, technologies, and laws. The public health emergency was a severe challenge to health institutions such as hospitals, the Centers for Disease Control and Prevention (CDC), and governments [7,12]. The solutions to these challenges were characterized by sustainability, redundancy, and flexibility [13]. Monetary and technology resources can merge the roles and responsibilities of public health preparedness and emergency management [14]. Severe deficiencies in legal preparedness can undermine effective responses to public health emergencies [15,16]. These were the essential factors in dealing with public health emergencies. Additionally, many countries took corresponding measures to strengthen the emergency management of public health. For example, the USA established PHEM operations centers either independently in health departments or as a part of the overall command system in the government [17]. China established the PHEM system from the national level to the local level to be responsible for emergency preparedness and response in 2004 [17]. In March 2018, the Ministry of Emergency Management of the People's Republic of China was established, which was an integral part of the State Council. Thus, we can see that PHEM is still a timely topic for scholars and governments [18,19].
However, there are still some problems that need to be solved. To the best of our knowledge, there is little evidence about the differences that occurred between international and Chinese PHEM. Moreover, what are the hotspots and trends of PHEM? What are the main research forces of PHEM? It is necessary to sort out the characteristics of the development of PHEM and explore the hotspots of PHEM research. Additionally, we compared international and Chinese research on PHEM. Based on this situation, we reviewed the articles on PHEM that were published over the past nearly 30 years in international and Chinese journals. Then, we used the knowledge map method to reveal the research strengths, frontiers, and development trends in this field. Study conclusions are helpful to draw people's attention to public health emergencies, provide a reference for scholars to understand the current situation and trends of PHEM, and for government departments to formulate guidance strategies.

Data sources
Data were divided into two categories: international and Chinese data. According to the relevant authoritative research [20], the database of bibliometric methods should contain complete documents. A considerable amount of literature has shown that the Web of Science (WoS) is the largest comprehensive academic information resource, covering peer-reviewed journals with high impact factors [21][22][23][24]. Accordingly, the international data used for our study were collected from the WoS Core Collection, including Science Citation Index Expanded (SCI-E), Science Citation Index Expanded (SSCI), and Arts & Humanities Citation Index (A&HCI) databases. Chinese data were downloaded from the China National Knowledge Infrastructure (CNKI), which had the largest Chinese journal full-text database, including the vast majority of Chinese journals relating to public health management. More importantly, it has become one of the critical basic data sources for bibliometric research in China [25].

Data retrieval
Data obtained by inappropriate literature information retrieval strategies could not accurately reflect the content of the research [26]. Emergency management is a common term in China that focuses on the occurrence, development, and evolution of emergencies and finding effective ways of responding to them [27]. However, it was not certified internationally. After consulting the experts from the Chinese CDC who once worked for the World Health Organization (WHO), we learned that the management was refined by preparedness, operation, response, and recovery for an international public health emergency. Additionally, this has been mentioned in articles [5,28]. Based on the above points, the international data retrieval strategies were set as: ((TS = public health) AND (TS = preparedness OR TS = operation OR TS = response OR TS = recovery) AND TS = (emergency)) AND LANGUAGE: (English) AND DOCUMENT TYPES: (Article) Indexes = SCI-EXPANDED, SSCI, A&HCI, Timespan = 1988-2018. When retrieving Chinese data, we choose "public health" and "emergency management" as the theme words, Timespan = 1988-2018. We ran the search query of WoS and CNKI on February 19, 2019. A total of 2759 articles from 1991 to 2018 were retained from WoS, while 999 articles from 2003 to 2018 were retained from CNKI.
After discussing the results with the team members, we further selected the articles based on inclusion and exclusion criteria to ensure that all of the data were closely aligned to the study targets. The inclusion criteria were as follows: (1) occurrence, development, and evolution of PHEM; (2) prevention, preparedness, response, operation, and recovery of the PHEM system; (3) planning, organization, leadership, coordination, and control of public health emergencies; and (4) practice and method of PHEM. The exclusion criteria were as follows: (1) health care, medical record management, or disease treatment; (2) guidelines on the action, proceedings paper or book chapter, interviews, summaries of conferences, and patent abstracts. Finally, 2247 international articles and 959 Chinese articles were accepted for the analysis after data filtering and removing duplications. The international articles were downloaded in "plain text" format with a full record and cited references for classification and statistical analysis. The Chinese articles were downloaded in the "Refworks" format. Those downloaded data contained the list of authors, the title of the publication, the abstract, keywords, and so on. Accordingly, we obtained the data for this study. Figure 1 shows the specific search steps.

Data analysis tools
We used CiteSpace 5.5. R2 and Microsoft Excel 2016 for the data analysis. CiteSpace was a free Java-based application found by Chaomei Chen to analyze the potential knowledge contained in the scientific literature. It has been widely adopted for scientometric analysis in various scientific fields [29], and has achieved excellent results [30,31]. The parameters of CiteSpace for this study were set as follows: time slicing (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018), respectively), years per slice (1), term source (all selection), node type (author, institution, keyword, for Chinese and international data; country for international data), selection criteria (top 50), and visualization (cluster viewstatic, show merged network). The corresponding other settings were selected according to different study questions. Microsoft Excel 2016 was used for temporal distribution and polynomial prediction of the number of articles. It should be noted that the results of the CNKI database made by CiteSpace were presented in Chinese. To make it easier to read, we translated the Chinese results into English.

Data analysis strategies
This study involved using bibliometric and mapping knowledge domain analysis methods. Bibliometric methods provided an approach to identify the development trends or future research orientations by combining different tools and methods to analyze the articles [32,33]. It allowed researchers to generate information from historical data and indicators, such as keywords, authors, institutes, and countries [34]. We were mainly engaged in cooperation network analysis (including the network analysis of the authors, institutions, and countries) and co-word network analysis (including keyword co-occurrence network and burst detection analysis) in the mapping knowledge domain analysis. First, we performed a statistical analysis of the temporal distribution of relevant articles. Then, we made a polynomial prediction of the number of articles, fitted the trend line of international and Chinese study, and predicted it for the next 3 years. Cooperation network analysis was used to analyze the contribution to different authors, institutions, and countries in one field. It was obvious that the more an author, a country, or an institution publishes its research findings, the more contributions it will make [35]. Betweenness centrality is an index to measure the importance of nodes in the network. The purple circle represents documents with betweenness centrality not less than 0.1, which means that the authors, institutions, or countries occupied an essential position in this field [20,36]. Co-word analysis was a content analysis technique that was effective for mapping co-occurrence relationships and the strength of the relationship between a pair of items existing in the same text, revealing the inner construction of a research field [24]. Analysis of the keyword co-occurrence network was meaningful and valuable for exploring timely topics in a specific knowledge domain [37,38]. In addition, keyword burst detection analysis can clearly grasp articles that receive particular attention from related scientific communities in a certain period. Therefore, the frontiers founded by burst detection analysis can provide researchers with up- to-date information [39,40]. The analysis of the highly cited articles in the field can reflect the development of the discipline in a period, examine timely topics, and supplement the above results to provide a reference for topic selection by scientific researchers [41].

Results
Temporal distribution analysis countries, yet a large number of Chinese scholars participated in this study at the beginning.
After the descriptive analysis of the data, we conducted a polynomial prediction analysis of the number of articles and predicted it for the next 3 years. The trend of chronological distribution of articles related to PHEM in international data can be expressed as follows: y = 0.2790x 2 + 0.7688x−7.7708 (R 2 = 0.9577), while Chinese data was y = −0.0345x 3 + 1.5079x 2 −14.142x + 27.273 (R 2 = 0.9251). Y indicates the number of articles, and x indicates the years. R 2 > 0.9, indicating a good degree of fit. The chronological distribution of international articles showed a trend of increasing year by year. In 2019-2021, the annual number of articles will exceed that of previous years. At the same time, the trend line of Chinese articles, such as a wave line, and the number of articles will continue to decrease over the next 3 years. In addition, as time goes on, the gap in the number of articles in Chinese and international journals will be gradually increasing. Figure 3, which shows the international co-author network, shows that there have been many authors writing . However, all three items' centrality was less than 0.1. In Fig. 4, the top-ranked item for Chinese scholars by citation count was Qunhong Wu with a citation count of 22. She was followed by Yanhua Hao (17), Feng Han (11), Ning (10), Yadong Wang (10), Zheng Kang (8), Ying Liu (6), Jincheng Ma (6), Mingli Jiao (5), and Libo Liang (5). Most of them were teachers at Harbin Medical University. The top-ranked items by centrality were Yanhua Hao and Ning, with a centrality of 0.02. The third one was Qunhong Wu, with a centrality of 0.01. Their nodes' centrality is also less than 0.1. In terms of the quantity and quality of articles, Qunhong Wu and Yanhua Hao were the leaders of PHEM in China. From the co-author network, we can see that many authors internationally and   Table S1, Table S2, and Figure S1).

Co-institution
Similar to the co-author situation, many institutions have studied PHEM (Figs. 5 and 6). The top-ranked item by international citation count was the Centers for Disease Control and Prevention (Ctr Dis Control & Prevent.), with citation counts of 255, which means that the institution publishes the largest number of articles in this field. The second one was Johns Hopkins University (Johns Hopkins Univ.), with citation counts of 92, which means that Johns Hopkins University had the largest number of articles published among the universities in this field. Johns Hopkins was followed by Harvard University (Harvard Univ.), Columbia University (Columbia Univ.), and so on. The above analysis showed that the CDC and universities were the leading institutions to study international PHEM. The centrality ranked item was CDC (0.50). Then, Johns Hopkins University (0.21), Harvard University (0.16), University of Washington (Univ Washington., 0.13), University of Toronto (Univ Toronto., 0.10), University of Pittsburgh (Univ Pittsburgh, 0.10), and Boston University (Boston Univ., 0.10) followed. The centrality of all these nodes was no less than 0.1 with the purple circle, which meant that they were the institutions with higher publication quality and the leading institutions in this field. The top-ranked item by citation count in the Chinese database was the School of Health Management, Harbin Medical University, with a citation count of 20, followed by Shanghai Publishing and Printing College (9) Table S3, Table S4, and Figure S2).  [42], these were all high-income countries except China. Geographically, half of them are centralized in Europe. Among these countries, the USA was the most productive, far ahead of the rest in this field, and its centrality was the largest. This showed that in the field of PHEM, the USA carries out the most studies, and their studies were more advanced. Although China ranks fifth on this list, its centrality was only 0.03. Therefore, these results indicate that Chinese scholars could publish some internationally recognized articles in the field, which would offer an advantage in quantity; however, they need to improve their article quality. It is worth noting that although the number of articles from Switzerland (44) and Sweden (34) was much lower than that of the USA, the articles' centrality of these two countries was more than 0.10, which showed that the quality of the articles was still high.

Co-word network analysis Keywords co-occurrence network analysis
Generally, keywords represent the research hotspots, which represent topics of wide concern for researchers in this field. Figure 7 shows that the top 10 keywords ranked by citation count for the international database were public health (297), preparedness (215), emergency preparedness (    preparedness and monitoring for public health events, while Chinese research mainly focuses on analysis and disposition (Additional file 1: Table S5, Table S6, and Figure S3).  Figure S4). To further explain the above research hotspots, the top 8 cited articles are shown in Tables 2 and 3 article Elevated blood lead levels in children associated with the flint drinking water crisis: a spatial analysis of risk and public health response was the most cited (372) international article [43] followed by The 2006 California Heat Wave: Impacts on Hospitalizations and Emergency department visits [44]. In terms of the time distribution, the research on international bioterrorism started first [45], followed by recommendations for health emergency response teams and health incident management [46,47]. In recent years, the causes and disposal of public health events have been the hotspots of international attention [43,[48][49][50]. This was basically consistent with the analysis results of the above research keywords. The top 8 Chinese cited articles of PHEM appeared in 2003, 2004, 2009, and 2011. Table 3 shows us that the most frequently cited Chinese article was Emergency logistics [51], written by Zhongwen Ou, Huiyun Wang, and Dali Jiang et al. with a frequency of an astonishing 473. This was followed by Kaibin Zhong's article Review and prospect: construction of emergency management system in China [52]. The next three articles, Legislative situation and characteristics of China's emergency

Discussion
International research on PHEM occurred earlier than the Chinese research, and it has been growing over time. This means that international scholars have paid increasing attention to PHEM. In 1991, the first article on PHEM was written by Richard L. Siegel and was titled Code 9: a systematic approach for responding to medical emergencies occurring in and around a hospital [56]. It mentioned the need for an organized system to respond to such emergencies involving patients, visitors, local community residents, and hospital employees, both inside the hospital and on the grounds surrounding the building. He recommended the establishment of a systematic emergency response system in all health care institutions. Since then, academia has begun to pay attention to emergency management of public health incidents. The number of international articles is increasing gradually, reaching the maximum in 2017, and it is expected to continue to grow in the next 3 years. The development of PHEM in China shows a fluctuating pattern. The occurrence of public health emergencies in the 10 years from 2006 to 2016 showed a general trend of first rising and then slowly declining. It is likely related to the number of significant events that occur in each year [57]. The severe acute respiratory syndrome (SARS) epidemic in 2003 resulted in significant increases in both the amount of research and articles on emergency management [7]. The number of articles reached a small climax in 2008. Events such as the Wenchuan earthquake and the southern snow disaster occurred in that year. The maximum was in 2013, with human infection from H7N9, the Ya'an earthquake, and death from a hepatitis B vaccine occurring that year. Moreover, 10 years after the SARS outbreak, some authors compared the development of PHEM in China over the 10-year period. The first Chinese article on PHEM was written by Tiewu Jia and was titled Capacity-building for public health emergency response to disasters (2003) [58]. This article was published during the epidemic of SARS. In 2003, China did not establish a network and echelon PHEM system. The author combined the development of emergency management, reform of health and epidemic prevention institutions, and discussed the capacity building of public health emergency response. It is helpful for the social function orientation of the disease control center and the improvement of disease prevention ability. Although the number of Chinese articles decreased in the following years, it remained above 48. In summary, the above analysis shows that PHEM is still a timely topic. From the perspective of cooperative networks, we find that there is more cooperation among Chinese authors but less cooperation among authors from different institutions. The cooperation between different research institutions is believed to be highly effective in facilitating high-level and fruitful research, which can also help develop the research field into a more established area [59]. Therefore, Chinese scholars should strengthen cooperation between different institutions. The research institution focus on PHEM mainly comes from universities and health institutions, while Chinese institutions have regional differences. Reasons include the following: the western region had poor fiscal capacity, a limited personnel size, and an inadequate stockpile in terms of working budget, timely reserves, and prompt delivery [60]. As a leader in international PHEM, the CDC has begun to help other entities strengthen their capacity, recognition, and technical expertise to strengthen their  PHEM capacity [61]. Additionally, some other health institutions, such as the WHO, have promoted development in this field. In 2005, the 58th World Health Assembly (WHA) adopted the revised International Health Regulations, which instructed the WHO member states to collaboratively confront public health emergencies of global significance [5,17,62]. Universities have undertaken the scientific task of PHEM, and they have conducted in-depth research on it in China. The Chinese CDC has carried out more disease prevention and control services, but its scientific research ability is weak. The country network analysis shows obvious differences in regional and economic development levels for PHEM. Those countries with more developed health emergency management systems are the most high-income ones. Geographically, most of these countries are concentrated in Europe, where the numbers of publications and citations are also significantly higher [60]. The USA, the UK, Japan, and other countries have constantly built and improved their PHEM systems, which have become a comprehensive management network. Co-word analysis of PHEM international research is more complex, extensive, and multidimensional. It reflects some of the major ideas of this research. Based on these ideas, scholars mainly focused on emergency preparedness and monitoring of public health events. From the perspective of Chinese PHEM development, it has gone through a process from theory to preparation, disposition, response, evaluation, organization, and discussion. That is, the main contents of China's health emergency management include the prevention and preparation of health emergencies as well as the key links of disposition, evaluation, and management, system construction, personnel training, and so on. The development of the whole discipline is therefore systematic and clear. The keywords with the strongest citation burst for international research on PHEM started with terrorism and bioterrorism [63], followed by disaster planning and emergency preparedness. In recent years, epidemics and infectious diseases have become the new research frontier. From the perspective of the whole development context, international research on PHEM has been related to current affairs hotspots, such as terrorism, which may have originated from the 911 incident, and epidemics, which may be related to the epidemic of infectious diseases caused by viruses and bacteria such as the Ebola virus. The study of PHEM in China is a process from theory formation to practice discussion, involving many links of management. During 2003-2008, Chinese scholars focused on health emergency response and disposition. After that, Chinese scholars began to learn more about foreign PHEM models. Some new methods have gradually been applied to Chinese PHEM in recent years.
The top-ranked articles by citation for the international knowledge domain of PHEM appeared in 2005, 2007, 2009, 2014, 2015, and 2016. In 2005, Lawrence M. Wein [45] developed a mathematical model of a cow-toconsumer supply chain to reduce bioterrorism events. Once again, it shows that international emergency management research is based on terrorism and bioterrorism. In 2007, Nathalie Embriaco focused on the working condition of emergency management personnel [46]. Kim Knowlton [44] and Salim S. Abdool Karim [47] mentioned the emergency department. The above three articles are all about the factors involved in health emergency management. The remaining articles analyze the specific events involving the mechanism, response, and recovery [43,[48][49][50]. From the above analysis, it can be seen that terrorism, emergency response and health incident management, and the disposition of public health events are the hotspots of international attention. Legislative situation and characteristics of China's emergency law [53], Legal construction of public emergency response in China: legal construction task proposed by SARS crisis management practice [54], and The realistic subject of administrative rule of law in public emergency management [55] were published in 2003. All three articles discussed the problems existing in the construction of the administrative legal system under the background of SARS. After that, three articles were published in 2004, mainly studying the mechanism and structure of PHEM in China. This research proposed the need to establish the emergency response mechanism for PHEM and establish emergency structure construction as soon as possible. In 2009, Kaibin Zhong wrote the article Review and prospect: construction of emergency management system in China [52]. He elaborated on the core contents of Chinese PHEM construction, including emergency plans, emergency structures, emergency mechanisms, and legal systems. China's PHEM integrates emergency systems, emergency mechanisms, and legal systems in an all-round way, which is characterized by comprehensiveness, institutionalization, openness, and guarantees. In 2011, The status quo of emergency management system for sudden public health events in America and Japan and its enlightenment [64] was published, showing that China has been learning the theory and experience of PHEM from some advanced countries. From the above analysis, it can be seen that the legal system, mechanism, and structure, system, and learning from abroad are the theoretical guidance for Chinese PHEM in the past 30 years.
Admittedly, there are some limitations to this study. First, the conclusions drawn from this study were based on only two large literature retrieval libraries. Other databases, such as Embase and Springer Link, were not studied. Not being able to search all the literature in this field may lead to incomplete retrieval results. Second, CiteSpace has some shortcomings in processing the results of the Chinese database; it cannot translate the result from Chinese into English directly. Third, there is a 1-year or longer time lag between our paper submission and its publication. The database articles may change during this time. Fourth, we conducted a comparison between Chinese and international databases similar to that performed in many other studies. It should be acknowledged that the two databases had different acceptance ratios, and this difference in data sources might lead to bias in the study results. In addition, we categorized English articles focusing on China as being part of the international database and did not analyze them alone. Although only a small part of the total, this may have created some deficiencies. This limitation may constitute an object of future studies, namely, those analyzing the differences between English papers focusing on China vs. Chinese papers.

Conclusions
In summary, we selected two large retrieval library documents to define the PHEM domain and detected the research status and the trends related to it from 1991 to 2018. According to the analyses, the conclusions are as follows. In the next 3 years, the number of international PHEM articles will continue to increase, while the number of Chinese articles will decline. Chinese scholars show less cooperation among different organizations. There are differences in regional and economic distribution between international and Chinese cooperation networks. China focuses on the east regionally, while developed countries and European countries have a more international focus. International research often relates to timely issues, mainly by focusing on emergency preparedness and monitoring of public health events, while China focuses on public health emergencies and their resolution. The international research on PHEM begins with terrorism and bioterrorism, followed by disaster planning and emergency preparedness, and emerging infectious diseases. China uses SARS as the research background and the legal system construction as the research starting point, which is followed by the mechanism and structure, system, and training abroad.