Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States (PLoS, abstract, edited)
Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States
Jeffrey Shaman 1*, Virginia E. Pitzer 2,3,4, C?cile Viboud 2, Bryan T. Grenfell 2,4,5, Marc Lipsitch 6,7,8
1 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, United States of America,
2 Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America,
3 Center for Infectious Disease Dynamics, Pennsylvania State University, State College, Pennsylvania, United States of America,
4 Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America,
5 Woodrow Wilson School, Princeton University, Princeton, New Jersey, United States of America,
6 Center for Communicable Disease Dynamics, Harvard School of Public Health, Harvard University, Boston, Massachusetts, United States of America,
7 Department of Epidemiology, Harvard School of Public Health, Harvard University, Boston, Massachusetts, United States of America,
8 Department of Immunology and Infectious Diseases, Harvard School of Public Health, Harvard University, Boston, Massachusetts, United States of America
Abstract
Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent reanalysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here, we extend these findings to the human population level, showing that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions.
Author Summary
The origin of seasonality in influenza transmission is both of palpable public health importance and basic scientific interest. Here, we present statistical analyses and a mathematical model of epidemic influenza transmission that provide strong epidemiological evidence for the hypothesis that absolute humidity (AH) drives seasonal variations of influenza transmission in temperate regions. We show that the onset of individual wintertime influenza epidemics is associated with anomalously low AH conditions throughout the United States. In addition, we use AH to modulate the basic reproductive number of influenza within a mathematical model of influenza transmission and compare these simulations with observed excess pneumonia and influenza mortality. These simulations capture key details of the observed seasonal cycle of influenza throughout the US. The results indicate that AH affects both the seasonality of influenza incidence and the timing of individual wintertime influenza outbreaks in temperate regions. The association of anomalously low AH conditions with the onset of wintertime influenza outbreaks suggests that skillful, short-term probabilistic forecasts of epidemic influenza could be developed.
Citation:
Shaman J, Pitzer VE, Viboud C, Grenfell BT, Lipsitch M (2010) Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States. PLoS Biol 8(2): e1000316. doi:10.1371/journal.pbio.1000316
Academic Editor:
Neil M. Ferguson, Imperial College London, United Kingdom
Received:
September 10, 2009; Accepted: January 20, 2010; Published: February 23, 2010
This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
Funding:
This work was supported, in part, by the US National Institutes of Health (NIH) Models of Infectious Disease Agent Study program through cooperative agreements 5U01GM076497 (ML) and 1U54GM088588 (ML and JS). VEP and BG were supported by NIH grant R01GM083983-01, the Bill and Melinda Gates Foundation, the RAPIDD program of the Science and Technology Directorate, US Department of Homeland Security, and the Fogarty International Center, NIH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests:
The authors have declared that no competing interests exist.
Abbreviations:
AH, absolute humidity; P&I, pneumonia and influenza; RH, relative humidity; RMS, root mean square
* E-mail: jshaman@coas.oregonstate.edu
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<cite cite="http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000316?utm_so urce=feedburner&utm_medium=feed&utm_campaign=Feed% 3A+plosbiology%2FNewArticles+%28PLoS+Biology%3A+Ne w+Articles%29">PLoS Biology: Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States</cite>
Jeffrey Shaman 1*, Virginia E. Pitzer 2,3,4, C?cile Viboud 2, Bryan T. Grenfell 2,4,5, Marc Lipsitch 6,7,8
1 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, United States of America,
2 Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America,
3 Center for Infectious Disease Dynamics, Pennsylvania State University, State College, Pennsylvania, United States of America,
4 Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America,
5 Woodrow Wilson School, Princeton University, Princeton, New Jersey, United States of America,
6 Center for Communicable Disease Dynamics, Harvard School of Public Health, Harvard University, Boston, Massachusetts, United States of America,
7 Department of Epidemiology, Harvard School of Public Health, Harvard University, Boston, Massachusetts, United States of America,
8 Department of Immunology and Infectious Diseases, Harvard School of Public Health, Harvard University, Boston, Massachusetts, United States of America
Abstract
Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent reanalysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here, we extend these findings to the human population level, showing that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions.
Author Summary
The origin of seasonality in influenza transmission is both of palpable public health importance and basic scientific interest. Here, we present statistical analyses and a mathematical model of epidemic influenza transmission that provide strong epidemiological evidence for the hypothesis that absolute humidity (AH) drives seasonal variations of influenza transmission in temperate regions. We show that the onset of individual wintertime influenza epidemics is associated with anomalously low AH conditions throughout the United States. In addition, we use AH to modulate the basic reproductive number of influenza within a mathematical model of influenza transmission and compare these simulations with observed excess pneumonia and influenza mortality. These simulations capture key details of the observed seasonal cycle of influenza throughout the US. The results indicate that AH affects both the seasonality of influenza incidence and the timing of individual wintertime influenza outbreaks in temperate regions. The association of anomalously low AH conditions with the onset of wintertime influenza outbreaks suggests that skillful, short-term probabilistic forecasts of epidemic influenza could be developed.
Citation:
Shaman J, Pitzer VE, Viboud C, Grenfell BT, Lipsitch M (2010) Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States. PLoS Biol 8(2): e1000316. doi:10.1371/journal.pbio.1000316
Academic Editor:
Neil M. Ferguson, Imperial College London, United Kingdom
Received:
September 10, 2009; Accepted: January 20, 2010; Published: February 23, 2010
This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
Funding:
This work was supported, in part, by the US National Institutes of Health (NIH) Models of Infectious Disease Agent Study program through cooperative agreements 5U01GM076497 (ML) and 1U54GM088588 (ML and JS). VEP and BG were supported by NIH grant R01GM083983-01, the Bill and Melinda Gates Foundation, the RAPIDD program of the Science and Technology Directorate, US Department of Homeland Security, and the Fogarty International Center, NIH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests:
The authors have declared that no competing interests exist.
Abbreviations:
AH, absolute humidity; P&I, pneumonia and influenza; RH, relative humidity; RMS, root mean square
* E-mail: jshaman@coas.oregonstate.edu
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