Short-Range Human Travel Helps Trigger and Spread Flu Infections Each Year Interview with:

Ishanu Chattopadhyay, PhD Assistant Professor, Department of Medicine Section of Hospital Medicine Institute for Genomics and Systems Biology University of Chicago

Dr. Chattopadhyay

Ishanu Chattopadhyay, PhD
Assistant Professor, Department of Medicine
Section of Hospital Medicine
Institute for Genomics and Systems Biology
University of Chicago What is the background for this study? What are the main findings?

Response: It is estimated that flu kills thousands every year in US, some estimates put the yearly death toll to around 30,000 — that is just in US, and that is irrespective of whether a new virus emerges. But why do waves of the disease sweep the globe every year, as if on a schedule? It had been suggested before that the trigger is a specific change in weather conditions, specifically, when normally humid air turns dry.

In this new study, we explore this question in much greater detail than was possible before, bringing to bear massive amounts data, such as 150 million individual medical histories recorded over the last decade, along with massive climate datasets. What we found was both fascinating, and consequential — no single factor is responsible wholly, and it requires a complex, yet precise, mix of weather conditions, demographic makeup, socio-economic variables, vaccination coverage, antigenic drift states of the virus, and human traveling habits, among others, to trigger the seasonal epidemic waves.

Quite surprisingly, long range air-travel is far less important compared to short range ground travel. This work attempts to finally settle the lack of consensus in the scientific community on which factors are responsible, as well as each factor’s relative importance. What should readers take away from your report?

  1. No single factor can explain the clockwork precision of seasonal influenza. We need a combination of numerous factors to explain influenza epidemics’ dynamic.
  2. The implicated factors include weather variables, socio-economic variables, human population demographics, vaccination coverage, and the virus’s antigenic drift.
  3. Short-range human travel (rather than longer-range air travel) is strongly implicated in triggering and propagating infection waves.
  4. While the “recipe” for the trigger that we found is complicated, it produces results that hold up in cross-validation tests. What recommendations do you have for future research as a result of this work?

Response: We can explore intervention strategies that exploit our findings. While we cannot control weather, we can control some of the other variables such as travel habits, access to healthcare in specific regions etc. Also, we can better predict the path of the epidemic based on weather conditions, leading to perhaps better health outcomes across the country.



Conjunction of factors triggering waves of seasonal influenza

Ishanu Chattopadhyay, Emre Kiciman, Joshua W Elliott,
Jeffrey L Shaman, Andrey Rzhetsky

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Last Updated on March 2, 2018 by Marie Benz MD FAAD