Influenza: a scientometric and density-equalizing analysis
© Fricke et al.; licensee BioMed Central Ltd. 2013
Received: 5 November 2012
Accepted: 26 September 2013
Published: 30 September 2013
Novel influenza in 2009 caused by H1N1, as well as the seasonal influenza, still are a challenge for the public health sectors worldwide. An increasing number of publications referring to this infectious disease make it difficult to distinguish relevant research output. The current study used scientometric indices for a detailed investigation on influenza related research activity and the method of density equalizing mapping to make the differences of the overall research worldwide obvious. The aim of the study was to compare scientific effort over the time as well as geographical distribution including the cooperation on national and international level.
Therefore, publication data was retrieved from Web of Science (WoS) of Thomson Scientific. Subsequently the data was analysed in order to show geographical distributions and the development of the research output over the time.
The query retrieved 51,418 publications that are listed in WoS for the time interval from 1900 to 2009. There is a continuous increase in research output and general citation activity especially since 1990.
The identified all in all 51,418 publications were published by researchers from 151 different countries. Scientists from the USA participate in more than 37 percent of all publications, followed by researchers from the UK and Germany with more than five percent. In addition, the USA is in the focus of international cooperation.
In terms of number of publications on influenza, the Journal of Virology ranks first, followed by Vaccine and Virology. The highest impact factor (IF 2009) in this selection can be established for The Lancet (30.75). Robert Webster seems to be the most prolific author contributing the most publications in the field of influenza.
This study reveals an increasing and wide research interest in influenza. Nevertheless, citation based-declaration of scientific quality should be considered critically due to distortion by self-citation and co-authorship.
Zoonotic emergence of human infectious diseases leads to a global risk to public health. The Spanish flu in 1918/19, most probably originated in birds, caused approx. 50 million deaths worldwide . The experience of H5N1, with a case fatality rate of at least 50 percent in 2003, the outbreak of the “novel influenza” (H1N1) in 2009 caused concerns of a global spread of this pandemic with millions of deaths estimated. Fortunately, the H1N1 pandemic was less severe compared to earlier pandemics. Nevertheless, seasonal influenza is still a challenge to local public health sectors all over the world [2, 3]. In recent years, enormous efforts have been made to improve diagnostic and therapeutic methods. However, problems in prevention and control of influenza persisted due to rising urbanization and mobility [4, 5]. The global threat of an influenza pandemic is also a challenge for international and interdisciplinary cooperation. Since the first available publications at the end of the 19th century, the amount of publication dealing with influenza is substantially and continuously increasing. The vast amount of publications referring to influenza and the difficulties in handling disease once it emerged, illustrates the need of a sound evaluation of the scientific output. Therefore, the present study investigates research accomplishments and their distribution using scientometrics and density equalizing mapping in combination.
Data was retrieved from the database Web of Science (WoS) by Thomson Scientific and, for further specific analyses, in the Medline database (PubMed) by the U.S. National Library of Medicine. Additional data was interrogated from OECD Statistics (Gross domestic product (GDP), spending for research and development (R&D), number of researchers as full-time equivalent per thousand people employed) .
“Influenza”, “Flu” and “Grippe” was entered in the search field and combined with the Boolean operator “OR” to retrieve the overall number of items. Further investigations used the “Analyze Results” function and the “Citation Report” provided by the WoS database.
The timeframe covers the years from 1900 to 2009. Results from 2010 to 2012 were not considered due to incomplete data acquisition at the time of data query.
Items retrieved from the data query in WoS were analysed by publication date, country of origin, source title, author and institution. Findings were transferred to Excel charts and pictured in diagrams. Furthermore, all published items were analysed with the function “citation report”. For all publications referring to influenza, the total number of citations and the average citation per item (citation rate) were calculated. In this regard, the number of publications can be seen as an indicator of quantity of the research productivity. Citation analysis is used as an indicator for the impact of publications for the scientific community, and, in consideration of methodical limitations, for research quality. Country related data were presented by using density equalizing mapping procedures based on Gastner’s and Newman’s algorithm . These were used as described in previous studies . Using this approach, the size of territories (e.g. countries) was aligned in correspondence to the peculiarity of selected variables (e.g. the number of publications, the number of citations and the average citation per country). The resulting maps are thus distorted depending on the chosen parameter. Finally, cooperation between countries and institutions was investigated. A journal contribution published by at least two authors coming from different countries or institutions is defined as cooperation. Using a specially developed software module, the values for the cooperation of each pair of countries were visualized as vectors. The thickness and colour of a vector elucidates the number of international and institutional cooperation, respectively . To ensure legibility, a minimum threshold of ten cooperative activities was defined.
Amount of published items and citation behaviour
The query in the WoS database results in 51,418 publications with a reference to influenza. In the research timeframe, a continuous and accelerating increase of publications in this subject area can be determined, especially in the last decade. A first remarkable increase in influenza related research output in WoS can be noticed in 1918 to 1921. Almost half of all publications (48.7 percent) were published in the last ten years of the examined period (2000–2009). The most citations were found in 1998. A citation rate (CR) of more than 30 can be shown in 1942 and 1944 as well as 1991 to 2000.
Analysis of research origin and cooperation
Publications, citations and citation rates sorted by countries
Institutional analysis and cooperation
Research infrastructure in selected countries
Research infrastructure plays an important role in controlling infectious diseases. Identification and spread of Influenza virus and development of suitable vaccine are examples for the need of sufficient research networking. In this study we choose the USA and the European Union as comparable economic areas on the one hand. On the other hand China and Russia were also included in the analysis.
GDP (in Bill. $-Dollar), R&D in percent of GDP, Researcher (full-time equivalent per thousand people employed) and published items; average 2000-2008
In regard to the pandemics of the last century, the influenza has a strong historical relevance in medicine. The seasonal appearances every year as well as the appearance of H5N1 and H1N1 in the last ten years shows the challenges this infectious disease brings to the world community. Although the indisposition is known and the virus with its characteristics is identified since long, there are many open questions within the scientific community. Especially events like H5N1 and H1N1 outbreaks illustrate the need of further investigation in this field.
The objective of this study was to analyse the influenza research output quantitatively and qualitatively by using bibliometric tools and density equalizing procedures.
Looking at the geographical distribution of the publication efforts, the USA takes a predominant role. With the highest agglomeration of research institutions, the USA offers an infrastructure, that does not only lead to the highest publication rate, but also to the most numerous and intense cooperation on national and international level. Several publications suggest the dominance of the USA within the scientific community [11–13]. Analogous to the amount of papers published, the US-American publications were also cited most often. However, when looking at the average citations per publication, other countries seem to dominate. Vietnam and Indonesia, for example, deliver the highest citation rate per publication. Content-wise, 80 percent of these articles deal with H5N1. Both countries have been particularly affected by the outbreak of this disease. In the years 2004 and 2005, 290 people of the 520 deaths worldwide, died in one of these two countries. Here, the case fatality rate was above 50 percent . The research from these countries seems to have had a special influence on the scientific community.
The examination of the citation rate (CR) cannot lead to a distinct scientific evaluation of the publication effort of a country or an author. The smaller the amount of publications used for the calculation, the larger is the impact of a few articles that have been cited often. Thus, in this research, we used a threshold of 30 publications for the calculation of the CR in order to get valid outputs. Further, inaccurate citations and self-citations also distort parameters like the CR or the impact factor that are used to measure the quality of the scientific work.
The current study represents a first detailed scientometric analysis and visualization of scientific output in the field of influenza. Established scientometric tools and the method of density equalizing mapping were used. The majority of scientific output originates from the USA. The UK, Germany and Japan follow with considerable distance. The highest CR is found for Vietnam and Indonesia. Considering the quantitative scientific output and citation analysis, an increasing interest in the field of influenza must be recognized. However, scientometric tools e.g. citation rate, impact factor and h-index must also be seen critically due to distortion by self-citation and co-authorship. Further investigations are needed to improve the assessment of the scientific productivity.
Gross domestic product
Organization for economic co-operation and development
Research and development
Web of science.
We thank C. Scutaru for expert technical help.
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