In the context of the current outbreak of Ebola Virus Disease (EVD) rapidly spreading in certain Western African countries with secondary cases in the United States and Spain, Science-Metrix searched the PubMed (Medline) database for EVD-related articles through a keyword query and cross-tabulated the results with WHO EVD death data (accessed October 21, 2014).
The figure below shows the association between yearly EVD death toll and scientific publications on the virus. For approximately 20 years after the discovery of EVD following an outbreak in Zaire (now the Democratic Republic of the Congo) and Sudan, fewer than 50 scientific papers were published annually on the subject. In 1995, an outbreak in the Kikwit area of Zaire coincided with a spike in publications, with a similar trend observed during outbreaks in 2000, 2003 and 2007. Exceptionally, a rapid increase in the number of publications starting in 2008 and spiking in 2011 does not appear to have been associated with an outbreak of EVD (see note below for two possible explanations).
The ongoing outbreak that began in December 2013 has seen the number of publications on EVD soar. Providing a more detailed overview of this trend, the graph below shows the number of EVD deaths and publications per month from March to October 2014. In September 2014 alone, over 100 scientific articles on EVD were published compared to fewer than 20 in March 2014 when the outbreak was still in its early stages.
Taken together, these results produce compelling evidence that there is a strong correlation between the outbreak of EVD and the number of publications on the topic.
Two potential reasons for the 2011 spike in publications:
- In 2008, there were two imported cases of the Marburg virus (a haemorrhagic fever similar to EVD) in the Netherlands and the United States. This may have caused panic in the international community and a subsequent spike in publications in the period that followed. Given that the Marburg and Ebola viruses are sometimes grouped in the literature, this may have been picked up in the keyword search.
- A 2008 outbreak of Reston-Ebola in pigs in the Philippines may have further caused alarm in the international community as well as veterinary professionals, leading to an increased number of publications.