Real-time tracking of virus evolution

Trevor Bedford (@trvrb)
4 Aug 2017
SURP Seminar
Fred Hutch

We work at the interface of virology, evolution and epidemiology

Segue through data vizualization

Data tells a story

Charles Minard and Napoleon's 1812 campaign

If data are looked at in the right way, answers become immediately clear

Edward Tufte

Above all, show the data

A good graphic is honest

Barchart of average value

Box-and-whisker plot showing variation

Showing the data

To clarify add detail

"To clarify, add detail... Clutter and overload are not attributes of information, they are failures of design. If the information is in chaos, don’t start throwing out information, instead fix the design."
– Tufte

Evolution of Conus shells

Greenland rising

Small multiples and dimensionality

Mapping infection spread

John Snow and the founding of epidemiology

Global pandemic spread

Geographic distance does not describe pandemic spread

Shortest network path captures pandemic spread

My research

Methods focus on sequencing to reconstruct pathogen spread

Epidemic process

Sample some individuals

Sequence and determine phylogeny

Sequence and determine phylogeny

Localized Middle Eastern MERS-CoV phylogeny

Regional West African Ebola phylogeny

Global influenza phylogeny

Phylogenetic tracking has the capacity to revolutionize epidemiology


  • Influenza evolution
  • Ebola spread in West Africa
  • Zika spread in the Americas
  • "Real-time" analyses


Dynamics driven by antigenic drift

Drift variants emerge and rapidly take over in the virus population

This causes the side effect of evading existing vaccine formulations

Drift necessitates vaccine updates

We're trying to forecast which strains will take over in the coming year and inform vaccine strain selection


Virus genomes reveal factors that spread and sustained the Ebola epidemic

with Gytis Dudas, Andrew Rambaut, Luiz Carvalho, Marc Suchard, Philippe Lemey,
and many others

Sequencing of 1610 Ebola virus genomes collected during the 2013-2016 West African epidemic

Phylogenetic reconstruction of evolution and spread

Initial emergence from Guéckédou

Tracking migration events

Factors influencing migration rates

Effect of borders on migration rates

Spatial structure at the country level

Substantial mixing at the regional level

Regional outbreaks due to multiple introductions

Ebola spread in West Africa followed a gravity model with moderate slowing by international borders, in which spread is driven by short-lived migratory clusters


Zika's arrival and spread in the Americas

Establishment and cryptic transmission of Zika virus in Brazil and the Americas

with Nuno Faria, Nick Loman, Oli Pybus, Luiz Alcantara, Ester Sabino, Josh Quick,
Alli Black, Ingra Morales, Julien Thézé, Marcio Nunes, Jacqueline de Jesus,
Marta Giovanetti, Moritz Kraemer, Sarah Hill and many others

Road trip through northeast Brazil to collect samples and sequence

Case reports and diagnostics suggest initiation in northeast Brazil

Phylogeny infers an origin in northeast Brazil

Genomic epidemiology reveals multiple introductions of Zika virus into the United States

with Nathan Grubaugh, Kristian Andersen, Jason Ladner, Gustavo Palacios, Sharon Isern, Oli Pybus, Moritz Kraemer, Gytis Dudas, Amanda Tan, Karthik Gangavarapu, Michael Wiley, Stephen White, Julien Thézé, Scott Michael, Leah Gillis, Pardis Sabeti, and many others

Outbreak of locally-acquired infections focused in Miami-Dade county

Phylogeny shows introductions from the Caribbean and a surprising degree of clustering

Flow of infected travelers greatest from Caribbean

Clustering suggests fewer, longer transmission chains and higher R0

Genomic epidemiology of Zika in the US Virgin Islands

with Alli Black, Barney Potter, Gytis Dudas, Esther Ellis, Brett Ellis,
Kristian Andersen, Nathan Grubaugh, Leora Feldstein, and others
(and special thanks to Adam Geballe)

Preliminary analysis of 31 genomes shows multiple introductions to USVI

Important analyses, let's make them more rapid and more automated

Key challenges

  • Timely analysis and sharing of results critical
  • Dissemination must be scalable
  • Integrate many data sources
  • Results must be easily interpretable and queryable


Project to conduct real-time molecular epidemiology and evolutionary analysis of emerging epidemics

with Richard Neher, James Hadfield, Colin Megill,
Sidney Bell, Charlton Callender, Barney Potter,
and John Huddleston

Nextstrain architecture

All code open source at

Rapid on-the-ground sequencing by Ian Goodfellow, Matt Cotten and colleagues

Desired analytics are pathogen specific and tied to response measures


Bedford Lab: Alli Black, Sidney Bell, Gytis Dudas, Stephanie Stacy, John Huddleston,
Barney Potter, James Hadfield, Louise Moncla, Maya Lewinsohn

Influenza: WHO Global Influenza Surveillance Network, Richard Neher, Colin Russell, Andrew Rambaut, Marc Suchard, Philippe Lemey, Steven Riley

Ebola: Gytis Dudas, Andrew Rambaut, Luiz Carvalho, Philippe Lemey, Marc Suchard, Andrew Tatem

Zika: Nick Loman, Nuno Faria, Oli Pybus, Josh Quick, Kristian Andersen, Nathan Grubaugh, Jason Ladner, Gustavo Palacios, Sharon Isern, Gytis Dudas, Alli Black, Barney Potter, Esther Ellis

Nextstrain: Richard Neher, James Hadfield, Colin Megill, Sidney Bell, Charlton Callender, Barney Potter, John Huddleston