No other infectious disease event has captured the attention of the international health community in recent years like the Ebola outbreak. The current epidemic started in December 2013 leading to over 26.000 infected patients and more than 10.000 deaths [1] The outbreak reached global dimension as hospitals in the United States of America (US) and Europe are now treating patients returning from health missions in Ebola affected countries [2].

28 outbreaks were documented since 1976, which all, except the recent one, occurred in isolated regions. During the first epidemic in the Democratic Republic of Congo and the Sudan the Ebola virus was identified as a non-segmented, negative-strand RNA virus and placed within the Filoviridae family. Since then five distinct virus species were distinguished. Although the pathogenesis of the Ebola virus is intensively investigated worldwide, the undisputed identification of the natural reservoir has not been successful yet. Bats were implicated as a possible host for the Ebola as well as the related Marburg virus [3].

Despite the short time span since the discovery of the Ebola virus, scientists have authored a substantial body of related scientific literature worldwide. Nevertheless, it should be an ethical obligation of all industrialized countries to invest future capacities in research of this life-threatening disease and vaccination strategies as one of the most effective means to fight infectious diseases [4,5].

In order to cast a first light on the question of global research activity in this field since 1976, we present a combined scientometric and density equalizing study. It encompasses scientometric tools and advanced visualizing techniques such as density equalizing mapping [6] and draws a sketch of the global Ebola research architecture over the past 40 years. Scientometric analysis of the scientific output of individuals, institutions and countries is represented in the number of publications as well as citations and their bibliometric parameters. Density equalizing map projections (DEMP) are used as a state of the art technique to demonstrate the global architecture on the research output via distorted maps.

The data was analyzed using scientometric methods developed in the NewQIS project as previously described [7]. The analyzed data was retrieved from the Thomson Reuters Web of Science database (WoS) using the search term “Ebola” in the Science Citation Index Expanded (SCIE) and the Social Sciences Citation Index (SSCI) (time frame between the first description of the virus in 1976 and 2014). To limit our search to the original research articles, we used the WoS´s option for selecting the document type and included only “articles” in the analysis. Data was processed as previously described using a combination of scientometric tools with density equalizing mapping [8]. For the generation of density equalizing mapping, the Gastner and Newman’s algorithm was employed [6]. As parameters, citation quantities were determined using the “citation report” function (number of citations per article, the citation rate of countries, and authors), H-indices [9] along with other general operating figures (year of publication, country of publication, co-operations between different countries, language of publication, document types, subject areas, and journals). Also, author analysis, subheading-terms, and individual subject areas were examined. To evaluate the quality of a country’s publication output, we assessed the citation rate and the modified H-index [9].

In order to give an overview over the global Ebola research architecture, the current study employed the Web of Science and conducted the first analysis of the research output for the entire field since 1976. Other than the majority of infectious diseases that have been discussed in the scientific literature for more than a century (e.g. yellow fever or dengue [10,11]) the advent of Ebola research is recent and started from its first description in 1976 [12]. Therefore, Ebola research offers a rare opportunity to observe the entire development of a scientific field since all related publications are achieved in electronically accessible scientific databases. Overall, we found that the number of publications was constantly low in the years after 1976 and remained on a level of up to 20 publications per year. This is surprisingly low for a dangerous infectious disease but understandable since a biosafety level 4 laboratory is needed to carry out the research. Coinciding with the reemergence of the virus in Kikwit (located in the Democratic Republic of Congo) [13], research activity was evidently enforce dafter 1995.

With regard to the landscape of Ebola research analyzed in this study, US-American institutions contributed the largest amount of international research. This finding again demonstrates the leading role of the USA in science, as it is present in almost all other areas of biomedical research [14]. We also showed a particular strong involvement of German institutions in Ebola research. This might be explained by the local availability of numerous suitable research facilities that were established after the first European outbreak of the Marburg virus. This virus is termed the “forgotten cousin” of Ebola and also causes life threatening hemorrhagic fever [15]. The application of the number of the total population and socio-economic parameters changed the ranking of the nations: Whereas the apparent superiority of the USA research was put in perspective, the African countries that are traditionally most affected by the disease such as Gabon, Republic of Congo, Central African Republic, Cameroon and Uganda increased their ranking.

Only a few studies evaluated the worldwide research efforts in the field of tropical diseases. These also found a predominance of North American and European countries regarding overall research activity. As examples of countries where particular diseases play a significant role for the health of the public, only Brazil, where yellow fever is endemic [16], as well as Brazil and India, which are affected by Leishmaniasis, were among the 10 most prolific countries [17]. Even high prevalent infections such as malaria have not lead to a increased global impact of research originating from African countries [18].

From its first appearance in scientific databases Ebola research was characterized by a high percentage of collaborative studies as demonstrated in our study. It has been shown numerously that involved scientists benefits from the international cooperation [19]. Although the US is the favorite global cooperation partner for scientists from other countries, it had the lowest cooperation ratio in regard to its own overall publication activity. This might be caused by the fact that American scientists cooperate to a large extend with national colleagues due to the efficient and well-funded academic structure that is present in the US.

When focusing on the collaboration of institutions committed to Ebola research, we found a network that favors only a limited amount of institutions. This might be explained by the necessary prerequisite of Ebola research. The risks involved in handling the virus require the maximum biosafety level [20]. Research facilities that provide these resources are sparsely distributed throughout the world and its highest numbers are found in the US–the leading country of Ebola research output.

Subject categories in health research represent the interest of scientist in different aspects of a disease. In the beginning of Ebola research, publications dominated that were attributed to the categories of microbiology, internal medicine and virology. Then the field became more diverse including other subjects such as immunology, cell biology, pharmacology, and biochemistry. Research in the field of public health encompasses society-based measures to combat diseases. We want to point out that a lack of publication output regarding public health topics is apparent in the field of Ebola research, which is in sharp contrast to other tropical diseases [16].

In conclusion, we here present a first detailed analysis of the global Ebola research landscape. The collected data indicated that the efforts in scientific research have been constantly increasing since the time of discovery in 1976. The USA was identified as being the leading country and a total of more than 3000 publications.

However, the danger of the virus, the change in pattern of distribution and the neglect to put more emphasis on the development vaccines before the outbreak of 2013–2015 clearly point to the need that 1) research in the field of hemorrhagic fevers needs to be strengthened, 2) vaccine development should also be enforced for other neglected tropical diseases in order to prevent similar catastrophes in the future, and 3) research endeavors should be focused on the area of public health since we could identify a neglect in Ebola related public health research efforts.