Nipah Virus: An Exploratory Scientometrics Analysis, 1999-2018

The objective of the study is to perform scientiometrics analysis of the published literature related to NIPAH Virus globally using the Web of Science database, for the period 1999-2018 and to compare the results with two earlier studies. The analysis was based on the quantification by the type of publications, year, citations, geographical productivity, keywords, most preferred journals, leading publications, mapping of authors, priority research areas and productive institutes. There were 1301 Nipah articles with 64% research articles, 38849 citations, country USA with more productive authors, ‘Nipah virus’ the commonly used keyword, ‘Journal of Virology’ as preferred journal, Wang LF as productive author of a research group, Infectious diseases as the priority research area and the most productive institute as Commonwealth Scientific and Industrial Research Organization, Australia. The main findings of the two earlier studies agree with the current study. The recently reported outbreaks in Kerala and Siliguri would increase the research database and alert among the Indian researchers.


INTRODUCTION
Scientometrics studies refer to the quantification of all available written communication and their authorship by means of citation studies. [1] Nipah virus (member gene of Henipavirus) in the Paramyxoviridae family, has drawn attention as an emerging zoonotic virus in South-East and South Asian region. [2] It has become a great public health concern all over the world.
Nipah virus infections in humans were reported in Malaysia for the first time in 1998 [3] where pig farming was a major industry. [4] Cases continued and later emerged in Bangladesh/ India region in 2001. In 2015, there was a Nipah Virus outbreak in the Philippines, which affected 17 individuals. [5] In May 2018, an outbreak was reported in southern India for the first time, in Kozhikode and Malappuram districts of Kerala. [3] Currently, there exists limited published literature about NIPAH virus. Two earlier reported studies about Nipah virus were using WoS (1990-2010) database and Scopus database (1999-24 May 2018). The objective of the current study was to explore the published literature about NIPAH virus globally using Science Citation Index Expanded Web of Science (WoS) all database from the period 1999 to August 2018 and to compare the similarity of the results with the two earlier studies.

METHODS
In the current study, we preferred the use of Web of Science Core Collection is painstakingly selected, actively curating a database of the journals that researchers have judged to be the most important and useful in their fields. [6] Due to its wider coverage from 1900, it has gained importance and it picks up all original research articles, reviews, meeting abstracts, editorials, written communications like books, conference proceedings letters and reprints. The database was downloaded on 31 st August 2018 and the results were refined for the period1999 to 2018. The keyword used for the search was 'NIPAH VIRUS'(n=1301) by 'TOPIC' and were retrieved using the WoS database. The retrieved data were exported to Microsoft excel 2007 and Endnote software for descriptive analysis. The Impact factor of the published papers was obtained from Thomson Reuters Journal citation reports. The study was explored based on type of publication, publication by language, quantification of NIPAH virus by year of publication and number of citations, geographical distribution and productivity of the Nipah virus articles, keywords, preferred journals with the impact factors, leading Nipah publications with their citations and mean citation per year, Visualization and mapping of the authors, Nipah virus articles by research areas and productive institute in publication of Nipah articles.

Publication of NIPAH article by language
The majority of the published articles were in English (1288; 97.8%). The other languages used for publication were French, German, Polish, Spanish, Dutch and Romanian ( Table 2).     highest productivity while regions with mustard color had the lowest productivity.

Keywords
The authors' keywords of the Nipah articles were visualized using the freely downloadable software VOSviewer [7] and shown in (Figure 3). In VOSviewer, based on the minimum number of occurrences authors' keywords, the data was mapped. The size of the node for each keyword in the map represents its magnitude of occurrence in the retrieved Nipah articles. The larger the size of the node denotes the higher frequency of occurrence of the keyword. The keywords with yellow color denote the most recently used author keywords.
In the current study, the most commonly used keywords by the authors were 'Nipah Virus' followed by 'Hendra Virus' and 'paramyxovirus'. The recently used keywords by authors in the articles are 'Nipah', 'Vaccine', 'Pathogenesis', 'Interferon' and 'Antiviral'.

NIPAH publications in the first ten preferred journals with the impact factors
The most preferred journals were Journal of Virology, Emerging Infectious Diseases, PLOS One, Virology and more shown in (Table 3). Emerging Infectious Disease had the highest impact factor of 8.22 as per Thomson Reuters Journal citation reports. Out of the 10 top preferred journals, the country USA had published in 7 journals with the highest number of articles followed by England. [8] The ten-top leading Nipah publications with their citations and mean citation per year The article published in the journal 'Science' by Li et al. in the year 2005 was cited the maximum number of times (838) and mean citation was 60 per year ( Table 4). The second highly cited article was in the journal 'Cell' in the year 2008 with 718 citations and with a mean of 65 per year.  Visualization and mapping of the authors.
The Nipah downloaded database was visualized using VOSviewer portrays visualization of similarities and mapping of scientometrics networks. Using visualization techniques, the density maps were generated in which the color, circle size, font size and thickness of the connecting lines showed about the author's contribution and connectivity. Units with a similar color indicated one cluster or group of close units that of the authors. The link and strength of the co-authorship were measured by the thickness and connecting lines ( Figure 4). The numbers of publications two researchers have co-authored also have been considered. There may be more than one link between any pair of authors. The higher the relative link strength suggested, the stronger the co-authorship. The larger circle size or font size indicated greater productivity of the articles. [9] The map shows ten colours representing different closely related research groups. The maximum productivity co-authored group was shown as Wang IF followed by Daszak P, Broder CC, Luby SP, Lee B, Maisner A, Ksiazek T and Cunningham AA.

NIPAH virus articles by research areas
WoS showed 61 research areas or categories and the top 10 research areas in Nipah, with the number of publications in each area, are shown in the ( Table 5). Majority of the articles were from Infectious disease (87%) followed by Virology (72-76%) and Microbiology (70-73%) during the year 1999 to 2008 and it is also analyzed that during the year 2009-2018 the majority of the articles were from infectious disease (88-96%) followed by Microbiology (69-71%) and virology (65-73%).

Productive Institute in publication of Nipah articles
The total number of institutes that contributed to NIPAH was 346. The ten top productive institutes in NIPAH research are shown in (

DISCUSSION
The current study portrays the global scenario of Nipah virus related articles over a period of years (1999-2018) using the web of science database. The exploratory analysis was based on the type of publication, quantification by year and citations, the geographical distribution of productivity, keywords, most preferred journals for publication, priority publications with authors and citations, mapping of authors, priority research areas and most productive institute. Majority of the publications were research articles 839 (64.5%) and maximum publication (108) was in the year 2013 with 38849 citations. The productive authors were from the country in the USA and 'Nipah Virus' was the most commonly used keyword. Most of the articles were published in the Journal of Virology and mapping of authors with co-authorship related research group identified the leading researcher as Wang LF. The priority research area was Infectious diseases and the most productive institute was the Commonwealth Scientific and Industrial Research Organization, Australia.
The rare disease Nipah, has generated a countable number of research articles (839 out of 1301) across the country and when India viewed at a glance it was (25 research articles out of 36) and the maximum (8) was published in the year 2008,    The current WoS database of Nipah articles does not show any definite, pattern of growth. The findings were almost consistent with earlier reported studies (Table 7). A study by Safahieh [10] using WoS for the period 1999-2010 also showed that the publication growth was incremental up to the year 2010 and the average citations per publication were 24.8. The active contributing country was USA (41%) and the most productive institute and author were Centre for Disease Control and Prevention, USA and LF Wang respectively. Another study using the Scopus database for the period (1999-2018) by Gupta et al. (Table 7) also showed that the growth pattern was not steadily increasing but fluctuating. [11] The country USA accounted for the highest publication share (46%) of Nipah virus articles with average citation per year as 28.1% and the most productive institute and author were CSIRO, Australia and Wang LF respectively.

CONCLUSION
The scientometrics about rare disease Nipah virus shows the productivity of the scientific community across the globe. The main findings using the scientometrics analysis for a shorter period (1999-2010) and using the Scopus database does not show major changes. Every search tool has its own accessibility (cost) and style (like a categorization of research areas) and also strengths and weaknesses [12] but keeps the major findings alike.
The recent outbreak of Nipah virus in May 2018, was reported in Kerala and India's first Nipah virus victim town Siliguri after Kerala outbreak has created an alarming sign to health authorities. According to the World Health Organization (WHO), more than 600 cases of Nipah virus human infections were reported from 1998 to 2015. [13] The above outbreak research would lead to incremental growth in the existing databases (like WoS, Scopus, PubMed, Google Scholar, etc.) and alert among the Indian researchers.