Bundschuh et al. Parasites & Vectors 2013, 6:331 http://www.parasitesandvectors.com/content/6/1/331 RESEARCH Open Access Yellow fever disease: density equalizing mapping and gender analysis of international research output Matthias Bundschuh*, David A Groneberg, Doris Klingelhoefer and Alexander Gerber Abstract Background: A number of scientific papers on yellow fever have been published but no broad scientometric analysis on the published research of yellow fever has been reported. The aim of the article based study was to provide an in-depth evaluation of the yellow fever field using large-scale data analysis and employment of bibliometric indicators of production and quantity. Methods: Data were retrieved from the Web of Science database (WoS) and analyzed as part of the NewQis platform. Then data were extracted from each file, transferred to databases and visualized as diagrams. Partially by means of density-equalizing mapping makes the findings clear and emphasizes the output of the analysis. Results: In the study period from 1900 to 2012 a total of 5,053 yellow fever-associated items were published by 79 countries. The United States (USA) having the highest publication rate at 42% (n = 751) followed by far from Brazil (n = 203), France (n = 149) and the United Kingdom (n = 113). The most productive journals are the “Public Health Reports”,the“American Journal of Tropical Medicine and Hygiene” and the “Journal of Virology”. The gender analysis showed an overall steady increase of female authorship from 1950 to 2011. Brazil is the only country of the five most productive countries with a higher proportion of female scientists. Conclusions: The present data shows an increase in research productivity over the entire study period, in particular an increase of female scientists. Brazil shows a majority of female authors, a fact that is confirmed by other studies. Background and travel by plane. Due to the changing global epidemi- The yellow fever disease is an acute viral haemorrhagic ology of the disease, it is necessary to continuously update disease transmitted by infected mosquitoes [1]. The vast the risk areas for yellow fever [2]. majority of reported cases and deaths occur in tropical A number of recent studies have demonstrated the areas like Sub-Saharan Africa (about 90%) and to a lesser change of the epidemiology. It is known for example that extent in Central and South America. Yellow fever is yellow fever is endemic in many areas of Brazil. Moreno endemic in a total of 44 countries, including 32 African and Barata [3] demonstrated that outbreaks of yellow fever countries and 13 Central and South America countries have occurred in regions of Brazil where no reports had (e.g. Bolivia, Colombia, Ecuador and Peru). been registered for decades [3,4]. According to WHO there Despite improved prevention options due to the avail- are an estimated 200,000 cases of yellow fever causing ability of vaccination, yellow fever is still a major public 30,000 deaths annually worldwide with 90% occurring health problem in some countries and of prime import- in Africa. These global estimates of yellow fever disease ance, since new epidemics have occurred recently. The stem from the 1990s [5-7]. A recent analysis of African epidemiology of the yellow fever disease is a dynamic data sources due to be published later this year estimates process and dependent on climatic changes such as the similar figures for 1995, for the year 2013 approximately occurrence of rainfall or human factors such as migration 84,000 to 170,000 cases and 29,000 to 60,000 deaths of yellow fever [8]. * Correspondence: [email protected] The aim of our study was to perform an in-depth analysis Institute of Occupational, Social and Environmental Medicine, Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany of the quantity and quality of the yellow fever research © 2013 Bundschuh et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Bundschuh et al. Parasites & Vectors 2013, 6:331 Page 2 of 12 http://www.parasitesandvectors.com/content/6/1/331 output worldwide from 1900 to 2012 by using sciento- each journal. It can be used to compare the relative metric tools such the citation rate and h-index. We also importance of a journal in its scientific field [22-24]. examined the geographical distribution of items on yellow fever, analyzed the international cooperation and con- Comparison of countries ducted a gender analysis. Density Equalizing Mapping Projection (DEMP) was de- scribed by Gastner and Newman [25] which is the basis Methods of the NewQuis platform established by Groneberg-Kloft Data source et al. in 2008 [26]. With this method it is possible to Data were retrieved from the Web of Science (WoS) visualize the distribution of the total number of pub- database by Thomson Reuters. In order to approximate lished items and the average citation rate in a country- the overall number of published items on yellow fever, specific manner. Geographical regions are placed in data was analyzed regarding the following search term: relation to selected variables (e.g. the number of pub- “yellow fever” OR “fievre jaune” OR “gelbfieber” OR lished items on yellow fever and average citation rate). “vomito negro” OR “yellow jack”. In total 5,053 publica- Specific calculations were based on Gastner and Newman´s tions were identified and further analyzes were performed algorithms [25], published in 2004. These calculations using the function “citation report” and the “analyze use a diffusion equation in the Fourier domain bor- results” function of the WoS. rowed from elementary physics, which allows variable The present study is a scientometric analysis of the resolution by tracking moving boundaries [25]. scientific publications on yellow fever from 1900 to 2012 inclusively. Results from 2013 were not included in the Cooperation analysis study because the data collection from 2013 is not yet An analysis was performed with regard to the coopera- complete. tions between institutions, countries and authors. The By using scientometric tools an investigation was per- visual representation of the cooperations was conducted formed to assess quality and quantity of research activity in spider charts with different color intensity. for the total number of published items and citations, the average citation per item (citation rate), for single Gender analysis journals, for single countries and for single scientists. We examined the proportion of male and female re- The analysis is based on the NewQis platform [9]. searchers listed in the publications of yellow fever, the share of the first and last authorship in the different countries as well as regarding the subject areas. This NewQis proved to be problematic, in particular, with the assign- The NewQis platform is an international project that ment of Asian, especially Chinese names, which are not uses classical scientometric tools together with new assignable to a gender but always used for both genders visualisation techniques such as density equalizing cal- equally. Additionally some author’s Christian names were culations to visualize mapping of research activity and missing or only indicated as initials. Subsequently, not quality for benchmarking processes. The project is all author’s genders could be determined. Up to ap- entitled New Quality and Quantity Indices in Science proximately 50 percent of the overall authors could be (NewQis). NewQis can be used to compare countries, specified regarding their genders. institutions or scientists for their academic performance Since this research was not carried out on animals or and was established in 2009 [9]. Since then a large number humans, an approval was not needed. of studies using this platform have been published [10-19]. Results H-index Total numbers of published items This index is useful to examine the research performance The present study outlines a scientometric analysis of the of scientists, countries and institutions. It was developed scientific publications on yellow fever during the research by the American physicist Jorge Hirsch in 2005. Most of timeframe from 1900 to 2012. In total, 5,053 scientific the cited publications and the number of received cita- publications were identified in the WoS database. The tions are graded [20,21]). analysis revealed an undulating, fluctuating course but in total a continuously increasing process of items until Impact factor 2010. Most of publications are at the beginning of the The Impact Factor is another scientometric tool for 20th century (Figure 1). assessing the quality of a journal. A country-specific analysis showed the United States It is calculated from the number of citations of a journal as the most productive country, hence dominating the in a given period and the number of articles published in cartogram. The United States have published most of Bundschuh et al. Parasites & Vectors 2013, 6:331 Page 3 of 12 http://www.parasitesandvectors.com/content/6/1/331 Figure 1 Temporal evolution of the number of publication during the period of the study. Figure