What are the most studied and impactful pathogens in Europe? A UK research team decided to find out, and they’ve now published the top 100 human and top 100 animal pathogen lists in PLoS ONE (1).
It goes without saying that knowledge and prioritization of pathogen impact is important, and common methods to gather this information take values such as incidence of disease, mortality and morbidity, prevalence, and more, into account. But for many diseases, accurate data for those parameters doesn’t exist. Researchers from Liverpool University’s Institute of Infection and Global Health (along with collaborators from Montpellier University, France) have devised an alternative approach: the Hirsch Index (H-index) proxy.
They looked at the number of citations and original papers published concerning a pathogen, and concluded that the levels of interest and volume of research within the scientific community correlated with its impact burden. Sound far too simplistic? It is, but when comparing their list to those of the Global Burden of Disease Study (2) and the diseases prioritized by the European Commission (EC) (3), the researchers found a 42 percent correlation. Although this makes it far from perfect, the authors believe their method has applications; it’s fast, objective and evidence-based, and could be used both alongside other systems such as the EC’s, and alone to estimate disease impact when there is a lack of data.
We’ve taken a closer look at the top 10 human pathogens (Table 1) and included the full list (Table 2). Do you agree with the ranking? Feel free to leave a comment below.
Interesting Observations From Top 100 Pathogens Study
- There are very few fungi or helminths in the list and none within the top 10 (only one makes it into the top 20); the authors do not speculate why.
- There is an even split between bacteria and viruses (five of each) within the top 10.
- 43 pathogens occurred in both the top 100 human and top 100 animal rankings.
- Impact does not equal disease toll – WHO numbers estimate that more people die of HIV and tuberculosis than from any other single infectious agent. These pathogens hold spots 2, 3 and 10.
- Limitations of the H–index exist – false positives could result for pathogens frequently used as model organisms (such as E. coli); trends can occur for certain pathogens (i.e. studying them can become “fashionable”); literature unavailable in English wasn’t used; time lag between study and publication means emerging pathogens may be underrepresented (Ebola may be a good example: interest in this virus has grown exponentially in recent times, which means it’s H-index score may also increase).
Table 1. Information on the top 10 European pathogens, ranked using the H-index. * WHO estimate.
Table 2. The top 100 human pathogens.
- K. M. McIntyre et al., “A Quantitative Prioritization of Human and Domestic Animal Pathogens in Europe”, PLoS ONE, 9 [epub ahead of print] (2014). doi:10.1371/journal.pone.0103529
- C.J.L. Murray et al., “Disability-Adjusted Life Years (DALYs) for 291 Diseases and Injuries in 21 Regions, 1990-2010: a Syetematic Analysis for the Global Burden of Disease Study 2010”, Lancet, 380, 2197–2223 (2012).
- Commission Implementing Decision of 8 August 2012 Amending Decision 2002/253/EC Laying Down Case Definitions for Reporting Communicable Diseases to the Community Network Under Decision No. 2119/98/EC of the European Parliament and of the Council, OJ., L262/1 (2012).
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