Keywords

1 Introduction

In late December 2019, an emergence (COVID-19) was first diagnosed in Wuhan, China, occurring due to a novel coronavirus [1]. The coronavirus has now been rapidly spread to almost all parts of the world [2]. The global outbreak of the novel coronavirus disease or COVID-19 has been declared as a pandemic like Ebola, Zika, and Nipah by the World Health Organization (WHO) on March 12, 2020 [2]. This is now considered to be of major international concern toward public health. The coronavirus disease (COVID‐19) is triggered by 2019‐nCoV or most commonly known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), belonging to the β‐coronavirus cluster [3].

Earlier, the world has witnessed an endemic situation in Guangdong, China (2002), due to a severe acute respiratory syndrome (SARS) outbreak that was caused by SARS-CoV [4]. After a decade in the year 2012, an endemic occurred in the Middle Eastern countries that were caused by Middle East respiratory syndrome coronavirus (MERS-CoV) [5]. Both the SARS-CoV and MERS-CoV belong to the β-coronavirus subgroup.

According to the report of the World Health Organization (WHO), the COVID‐19 epidemic has already affected millions of people across the globe. The data itself is alarming, and the entire humanity is battling this era’s most gut-wrenching war. However, till date, in the absence of specific therapeutic drugs or clinically approved vaccines for COVID-19, intensive research is urgently needed on the newly emerged SARS-CoV-2 to identify potential drug targets and for the eradication of the pathogenic mechanisms and epidemiological characteristics for the development of effective strategies for its prevention and treatment.

Coronaviruses (CoVs) consist of a single-stranded positive-sense RNA genome encapsulated within a membrane envelope [6, 7]. The coronaviruses consist of glycoprotein spikes on its outer surface, which are responsible for the attachment and entry of the virus to the host cells [8]. The receptor-binding domain (RBD) is loosely attached among the virus, which allows the virus to infect multiple hosts [9]. Their genomes contain 29,891 nucleotides that encode for 9860 amino acids [10]. CoVs are classified into four genera: Alphacoronavirus (alphaCoV), Betacoronavirus (betaCoV), Deltacoronavirus (deltaCoV), and Gammacoronavirus (gammaCoV) [11]. The SARS-CoV-2 belongs to the betaCoVs category and has a round, elliptic, or pleomorphic form, which has a diameter of 60–140 nm (approx.) [12, 13]. Similar to the other CoVs, they are sensitive to ultraviolet rays and heat. SARS-CoV-2 also possesses the typical coronavirus structure with spike protein [2]. This spike protein consists of a 3-D structure in the RBD region, which interacts with the host cells through the Van der Waals forces.

As reported in the literature, the SARS-CoV-2 also uses the same angiotensin-converting enzyme 2 (ACE2) cell receptor and the mechanism, which was previously used by the SARS-CoV for its entry into the host cell [7, 14]. SARS-CoV-2, similar to SARS-CoV and MERS-CoV, also attacks the lower respiratory system that causes viral pneumonia. Further, the virus also affects the gastrointestinal system, liver, kidney, heart, and central nervous system that lead to multiple organ failure [15].

According to recent information, SARS-CoV-2 is more transmissible/more contagious than SARS-CoV [7, 16]. A published report has revealed that the binding affinity of SARS-CoV-2 S protein to ACE2 is about 10−20 times higher than that of SARS-CoV S protein, which is speculated to be the reason behind the high transmissibility and contagiousness of SARS-CoV-2 as compared to SARS-CoV [7]. At the onset of the COVID-19, the main symptoms include fever, dry cough, fatigue, headache, and sore throat [17].

In severe cases, the patients may suffer from dyspnea and/or hypoxemia one week after the onset of the disease. But sometimes patients with even no obvious fever, mild fatigue, and no pneumonia, known as asymptomatic cases, can also spread SARS-CoV-2 between humans. The spread of the deadly virus from human-to-human is known to be transmitted via droplets or direct contact. Thus, there has been an urgent need for coronavirus-based research for detailed analysis in recent years. This will help in the availability of analyzed data under one common umbrella and thus will be helpful in future research work related to coronavirus. Unfortunately, there is no such scientometric review of the coronavirus-based research till now. A considerable amount of knowledge can be gained in a specific domain by having a systematic literature review in a relatively short time [18]. One of the quickest methods is the bibliometric analysis to perform literature review of a specific area for a large number of publications [18]. The bibliometric analysis supports us by providing the current trends in research of a specific field along with detailed understanding of the various relationship of author citation and author cooperation etc.

In view of the above discussions, we propose to introduce the bibliometric analysis of research based on coronavirus so as to gain an insight of the influential authors, institutions, and countries involved in the said research field, the most cited research articles and journals, and lastly, the recent trends in the field of the study. For the bibliometric analysis, the records of publications were retrieved from the database of Web of Science.

2 Methodology

2.1 Data Source

Publication information was obtained using the search engine of Web of Science (WOS) database, SCI-Expanded, which was deemed as the optimal database, was analyzed via bibliometric analysis.

2.2 Search Strategy

All the publication information was extracted from the Web of Science, and the database was collected on April 16, 2020. In our study, the research terms used for searching the articles were as follows: The database search was conducted using the parameters: TS = ((coronavirus) OR (coronavirus)). There was no restriction on the timespan, which resulted in the fetching of the documents from the year 2000 to 2020.

2.3 Data Collection

The total number of documents obtained was 11,925. From the obtained pool of publications, the document type was restricted to “Article,” which reduced the count of publications to 9450. Further, the articles in “English” language were segregated. This process brought down the total number of documents to 9257. Then, the “full records with references” data of these publications were downloaded as.txt files with the Tab-delimited (Win, UTF-8) file format. The information on citations, bibliography, abstract and keywords, funding details, and all other information was exported as CSV files from the analyzed results of the Web of Science search engine.

2.4 Bibliometric and Visualized Analysis

The bibliometric analysis was performed using the VOS viewer software, developed by Van Eck and Waltman [19]. The intrinsic function of Web of Science was used to describe the essential features of the eligible desired publications network. These networks commonly include global researchers, journals, or individual publications and can be developed based on various factors like bibliographic couplings, citations, co-citations, authorship or co-authorship relationships, funding agencies, publication source, etc. The VOS viewer software creates a graphical representation of the bibliometric data [19]. The distances between the nodes within the graphical representation are related with the closeness between the nodes. Different bibliometric maps were generated and analyzed [18, 19].

3 Results and Discussions

3.1 Yearly Distribution and Trend of Growth

Altogether, a total 9257 number of articles were published on the topic related to coronavirus. This depicts that researchers and scientists had a great attraction and interest in this research field. The total count of publications that are published on year-on-year basis shows a good projection of the strength of research in a specific field. The analysis of the trends in the number of publications per year may divulge information on the research interest in the near future. A plot of the number of publications versus cumulative publications on a year-on-year basis was used to analyze the trend of research in the area of coronavirus in the past years (Fig. 1a). The analysis of the plot suggested that the research in the related field could be dated back to the year 2000. The highest number of publications (613 documents) was published in the year 2004. But in the year 2020, until now, i.e., 16 April 2020, 381 articles already had been published. The year 2002 has witnessed a very less number of publications (130 documents). Post-2002, there was an increase in the publications, which reached the maximum in the year 2004. This can be accounted for the fact that in late 2002, there was this SARS epidemic. Hence, there was a sudden increase in the field of coronavirus. However, post-2004, there was a decrease in the annual publications of articles until the year 2012. In late 2012, there was an outbreak of the Middle East respiratory syndrome (MERS). As a result of that, there was again an increase in the research in the field of coronavirus. Since the year 2014, the annual publications of the articles until the last year (2019) were similar. From the previous trends, it is quite expected that the number of publications is bound to increase in the year 2020. As a matter of fact, within the first three and a half months of the year 2020, nearly 400 articles on coronavirus have already been published. For the analysis of the graph of cumulative publications, the time period could be broadly divided into three main zones. The first zone of the period is between the years 2000 and 2004, wherein the research on coronavirus was increasing at a slow pace. Subsequently, during the period of 2004 to 2012, the momentum on the coronavirus research initially picked up. However, post-2006, the momentum was lost. In the third phase (2013–till date), there is a linear increase in coronavirus research. It is expected that the year 2020 will bring another turning point in coronavirus research across the globe.

Fig. 1
figure 1

Year-on-year publication information. a The number of publications and cumulative publications and b the number of publications and citations

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The variation in the citations received by the publications during the 2000–2020 time periods has been summarized in Fig. 1b. During the period 2000 and 2002, the citations of the publications on coronavirus received very fewer citations. Since the year 2003, the number of citations had increased unexpectedly, and the increasing trend continued until 2008. This was quite expected because the researchers across the globe had started working on the coronavirus that was instigated by the SARS outbreak. Thereafter, until the year 2012, there was a plateau phase in terms of citations received by the publications on coronavirus. This suggested that the research on

Fig. 2
figure 2

Country cooperation network on coronavirus (N.B: (1) Countries that published at least more than ten documents were considered)

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coronavirus reached a stagnant phase. Since 2013, the number of citations per year showed an increasing trend even though the number of publications has remained fairly constant. This observation can be explained by the fact that the researchers were trying to gain insight on the coronavirus from the previously published publications. The average citation per year is 12,437. Although the year 2020 has witnessed only just over 8500 citations, it is important to note that we are just within the first three and a half months of the year.

3.2 Country-Level Distribution of Publications

The 9257 number of documents was published from 126 countries, as tabulated in Table 1. The highest number of publications (3197 documents, 34.53% of the total documents) was reported from the United States of America (USA), followed by 2386 publications (25.77%) from Peoples R. China. Germany, the third rank holder, published 602 publications (6.50%). England and Netherlands were in fourth and fifth positions with 510 publications (5.50%) and 504 publications (5.44%), respectively. Further, the trend was followed by Japan, Canada, and South Korea. These countries had publications in the range of 406–470. Afterward, three countries that published documents were in the range of 329–366. Thereafter, five countries that published documents were in the range of 212–298, followed by another five countries that have published 115–189 documents. The analysis confirms the synergistic as well as a simultaneous approach between different countries in the area of coronavirus research. In total, 34 countries in the past had already published at least a hundred documents in the area of coronavirus. The statistics view of these countries is provided in Table 1. From the table, it is quite evident that 19 countries out of 56 countries had a nominal GDP rank below 20 indicating that the economically developed countries are carrying out research on coronavirus. The USA has the most number of 110,117 citations from the 3184 documents, followed by Peoples R. China, Netherlands, Germany, and England. The publications from these countries had received 65,472, 30,408, 28,688, and 17,734 citations, respectively. Interestingly, the average citation per documents of North Ireland was in the first position (72.33) from 15 documents, followed by the Netherlands with an average citation of 60.33 from a total of 604 documents. Germany, England, Finland, and New Zealand, respectively, were subsequently in order of the countries that had an average citation of 50 or higher. It is important to note that India is ranked twenty-first, in terms of the published number of documents with an average citation per document of 14.23.

Table 1 Top countries that published more than ten documents
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According to the VOS viewer manual, each and every link is assigned a strength, which is shown by a positive numerical value. The higher the value, the stronger is the link. In other words, the link and the assigned strength are directly proportional to each other. The TLS highlights the total number of publications with at least a common two keywords in the documents. The TLS also gives information related to the collaborative research in the common research area among different countries. The analysis of TLS, as shown in Table 1, suggested that USA, had TLS of 1941, was the most superior country by far in terms of collaborative research. USA was the major contributor in the area of coronavirus research and globally played a leading role. It was found that the USA had documents published in collaboration with many countries like Argentina, Cambodia, Egypt, Israel, Jordan, Nigeria, Pakistan, Qatar, Russia, Saudi Arabia, Tunisia, Turkey, and United Arab Emirates (Fig. 2). China was in the second position, with a TLS of 1123, followed by Germany in the third position with a TLS score of 799 in the collaborative research. The TLS score along with the cooperation network map suggests a strong research collaboration of many countries with USA and China. In the fourth and fifth positions were England and Netherlands, with a TLS of 626 and 697, respectively.

3.3 The Co-Authorship and Organizations Relationship

Further, the co-authorship and organization relationship was studied with a minimum number of documents of an organization and citations of an organization of being 10 and 1000 in number, respectively. Accordingly, the data of 150 organizations was obtained and is presented in Fig. 3 and Table 2. It shows that the University of Hong Kong was in the first position with 417 documents and 56.62 average citations. The TLS of the University of Hong Kong was 384. After the University of Hong Kong, the Chinese Academy of Science with 306 documents, 33.80 average citations, and 283 TLS was in the second position. The third position was occupied by the “Center for Disease Control and Prevention,” which have 191 documents, 55.87 average citations per document, and TLS of 210. Univ Utrecht and Chinese Academy Gramsci have 184 and 162 documents with 45.80 and 17.41 average citations and 170 and 45 TLS with other organizations.

Fig. 3
figure 3

Co-authorship—organizations of the researchers who are working in the area of coronavirus research. (N.B.: (1) Authors who have published at least ten documents were considered)

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Table 2 Co-authorship and organizations relationship
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3.4 Relationship of Authors and Co-Authors

The author and co-authorship network visualization map was created on the basis of bibliographic data gathered from the core collection. The analysis helps in identifying the major groups across the globe that is working in a research field related to coronavirus. This is achieved easily by mapping the relationship of authors with the co-author, as depicted in Table S2 and Fig. 4, respectively. Easy and visual representation of the relationship is obtained using the mapping process, which makes the study of both the individual activity of an author as well its interconnectivity with other research groups much easier. Figure 5 depicts five major groups (considering the presence of at least five authors in each group) that are working in the field of coronavirus. The research group of the author named Yuen Kwok-yung was the prominent group in the research field of coronavirus. Yuen Kwok-yung had the highest number of documents (number of documents = 120) among all other researchers, followed by Ralph S. Baric and Christian Drosten, with 111 and 109 total number of documents, respectively. The analysis of the TLS suggests that there is a significant research collaboration work among many of the researchers. However, some of the researchers are not involved in much research collaboration. It is of understanding that research collaboration improves critical information and knowledge flow among the different research groups all over the world. Extensive research collaboration among all the authors will definitely help in enhancing the improvement in the quality of the research on coronavirus. Further, Table 3 depicts the details of the count of published documents by the authors and their citation metrics, which helps to identify the most active researchers in this coronavirus research field. As already mentioned, the authors Kwok-Yung Yuen, Ralph S.Baric, and Christian Drosten had the highest number of published documents. However, the highest number of citations is of Ky Yuen, followed by Khandyuen Chan and Kwok-Yung Yuen, respectively, which indicated that these three authors are the most cited researchers on coronavirus across the globe. However, the information about the most impactful researchers can be provided by the average citations per document. In other words, a good quality paper can be identified by calculating average citations per document. It was found that W. Lim (documents: 14 citations: 411) followed by Lj Anderson (documents: 10 citations: 396), Adme Osterhaus (documents: 16 citations: 344), Ron A. M. Fouchier (documents: 11, citations: 245) and Theo M. Bestebroer (documents: 10, citations: 233) had the highest average citations per document. This is suggestive of the fact that the documents of W. Lim, Lj Anderson, Adme Osterhaus, Lj, Ron A. M. Fouchier and Theo M.Bestebroer were more impactful as compared to the others.

Fig. 4
figure 4

Authors and co-authors relationship of the researchers who are working in the area of coronavirus research (N.B.: (1) Authors who have published at least twenty-five documents were considered)

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Table 3 Top authors who published more than twenty-five documents
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3.5 Relationship of Distribution and Co-Citation

The relationship between sources and citations helps in concluding the interest of authors in which journals they prefer to publish their research results. The research articles that had published related to coronavirus in the important journals in the last twenty years are depicted in Table 4 and Fig. 5, respectively. From Table 4, it can be concluded that the most preferred and accepted choice is the “Journal of Virology” of many authors to publish their coronavirus-related research work. In the journal, till date 886 numbers of documents have been published with gathering 39,407 citations for the journal. The Journal “Virology” occupied the second position where 285 numbers of documents have been published with 7759 citations followed by the journal “PlOS One,” in the third position where 341 publications were published and had received 4488 citations for these articles. The aforesaid three journals had a good TLS, suggesting that these journals were highly cited. This observation can also be confirmed from the source-citation relationship map. The average citations per document provide an indication of the impactful publications that are published in the journals. Taking into account the average citations per documents, the top journals were The New England Journal of Medicine and Science with 15 documents, each with 530.27 and 419.90 average citations per document. Nature Medicine has 13 documents with 178.15 average citations per document. Also, the journals proceedings of the National Academy of Sciences of the United States of America have 111 documents but have105 average citations per document. Similarly, The Lancet Infectious Diseases has only 36 and 16 documents but has 240.2 and 118.56 average citations per document. Also, Nature Medicine has 13 documents with 178.15 average citations per document. This indicates that these journals published high-quality research work irrespective of the number of published documents.

Fig. 5
figure 5

Source and citations relationship of the sources that published documents on coronavirus research (N.B.: (1) Sources that have published at least ten documents were considered)

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Table 4 Top Journals where more than ten documents were published
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3.6 Document and Citations Relationship

The information about the quality of the documents published can be provided by studying the document and citation relationship. A higher quality of work is symbolized by a higher citation metric and thus has been cited by various researchers globally. As shown in Table 5 and Fig. 6, we have selected those documents having at least 300 times citations, which allowed us to narrow down the number of documents to 10 which in turn have been helpful in obtaining the highly cited documents related to coronavirus research. While fetching the collaboration map, the document by Allander et al. (2005) was not considered. The TLS of the publication was zero [20]. The top-cited document (1891 times) entitled “A novel coronavirus associated with severe acute respiratory syndrome” was reported by Ksiazek et al. [21]. The second most cited document described the “Identification of a novel coronavirus in patients with severe acute respiratory syndrome” by Drosten et al. in the same year, 2003 [22]. While the third most cited document was “Characterization of a novel coronavirus associated with severe acute respiratory syndrome” that was investigated by Rota et al. [23], and the fourth document also was reported in the year 2003 by Peiris et al. (2003) entitled “Coronavirus as a possible cause of the severe acute respiratory syndrome” [24]. Thereafter, the publication by Zaki Ali Moh [25] received a good number of citations. The topic of the study was “Isolation of a Novel coronavirus from a man with pneumonia in Saudi Arabia.” This means that these are the five documents that are followed by other high-quality documents in the research area of coronavirus.

Table 5 Top documents that have been cited for at least 300 times
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Fig. 6
figure 6

Documents and citations relationship of the publications that have been cited for at least 300 times

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Funding Agencies

Any funding agency plays a very important role by supporting and promoting research and development work in any specific area. Funding is among the most important pillars who is responsible for the growth of any subject area. Thus, we have extracted in total the top twenty global funding agencies who have supported funding in the area of coronavirus research as depicted in table S4. The United States Department of Health and Human Services (HSS) acquires the first position with the contribution of 17.58% of total research among 1628 documents related to the coronavirus research. It was followed by the National Institutes of Health (NIH), USA, being in the second position with 17.10% from 1583 documents. National Council for Scientific and Technological Development (CNPq) is being in the 20th position with 69 documents and 0.745%.

3.7 Identifying Coronavirus Infections and Health Condition by Density Visualization Map

The density visualization map was created by co-occurrence and analysis of the keywords (Fig. 7). Screenings of the keywords were done manually, such that only coronavirus and associated clinical symptoms or disease terms are selected for the density visualization map generation. The density visualization map analysis suggested that the coronavirus-related diseases are associated with severe acute respiratory syndrome. This is suggestive of the fact that even though there is a mutation in the coronavirus, which changes its characteristics, all of them precipitate severe acute respiratory syndrome.

Fig. 7
figure 7

Density visualization map of the coronavirus, major coronavirus-related infections and symptoms

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4 Conclusion

In light of the results of the scientometric analysis of the research paper, in the area of the coronavirus, there was a significant increase in various aspects, which includes the number of author appearances, number of multi-authored articles, etc. In gist, the information on 9257 number of documents related to the above-mentioned research area was extracted from the Web of Science. The extracted information was then used to perform a detailed scientometric analysis. It was observed that the research in this field of study started as early at 2000, but the research in the said field started receiving much attention post-2000. Since then from 2000 till 2020, research articles published reached a number of 9257. It was found that most of the economically developed countries were involved in the research related to the coronavirus. Also, the USA published the most number of documents followed by China. The USA had a TLS of 1941 indicating that the country was involved in extensive collaborative research. In terms of collaboration, China was in the second position. The University of Hong Kong was in the first position and was the most influential and impactful organization, having worked in the mentioned field of research with 417 documents with 56.62 average citations and TLS of 384, followed by Chinese Academy of Sciences with 306 documents, 33.80 citations, and 283 TLS. Other organizations like the Centers for Disease Control and Prevention, Utrecht University, Chinese Academy of Agricultural Sciences, The Chinese University of Hong Kong, and The University of North Carolina also received good attention from the researchers. The research groups of Yuen Kwok-Yung, followed by Ralph S. Baric and Christian Drosten, had the highest number of documents of 6176, 3843 and 5614, respectively. The scope for research collaboration across the globe is really very large, which, in turn, would definitely help in improving the overall research quality on coronavirus. The “Journal of Virology” has the highest number of 886 documents that have been published till date, and the documents were able to gain 39,407 citations for the journal. The journal “Virology” occupied the second spot by publishing 285 numbers of documents with 7759 citations. The top-cited document entitled “A novel coronavirus associated with severe acute respiratory syndrome” was reported by Ksiazek et al. (2003), which was found to be the most impactful documents in terms of average citations per documents. The document described as “Identification of a novel coronavirus in patients with severe acute respiratory syndrome” was cited as the second most by Drosten C et al. in the same year. United States Department of Health and Human Services is the highest supporter funding agency in coronavirus research among all other agencies globally.