Who infected whom? Creating a database of transmission trees for comparative outbreak analysis

Juliana Taube, a student at Bowdoin College, worked with Paige Miller and Dr. John Drake.

Abstract: Transmission trees contain valuable details about who infected whom in infectious disease outbreaks. We created a database with 81 published, standardized transmission trees consisting of 12 directly-transmitted pathogens (mostly viruses). We also demonstrated how the database could be used to help answer research questions in infectious disease epidemiology. First, we analyzed overall and pathogen-specific patterns between tree parameters (Rand variation in secondary infections). We found that outbreak size is nonlinearly associated with Rand the dispersion parameter, but emphasize that pathogen-specific patterns and intervention efforts may alter theoretical relationships between these variables. Second, we examined how superspreader contribution to onward transmission, either directly or through their tree descendants, varies across pathogens. Superspreaders were responsible for most cases via their descendants and the number of superspreaders varied across pathogens. Additional database exploration matched theoryabout how the proportion of superspreaders increases at intermediate levels of dispersion, an idea that should be further explored. We hope that our database will assist both theoretical and applied infectious disease epidemiology research in the future. 

1. Lloyd-Smith, JO, Schreiber, SJ, Kopp, PE, & Getz, WM (2005) “Superspreading and the effect of individual variation on disease emergence.”Nature438(7066): 355.