Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature
<!-- end title area --> <!-- start authors --> http://pathogens.plosjournals.org/pe...l.ppat.0030151
Anice C. Lowen<sup>1</sup><sup>*</sup>, Samira Mubareka<sup>1</sup>, John Steel<sup>1</sup>, Peter Palese<sup>1,</sup><sup>2</sup><sup>*</sup>
<!-- end authors --><!-- start affiliations --> 1 Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America, 2 Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
<!-- end affiliations --><!-- start: abstract --> Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. Twenty experiments performed at relative humidities from 20% to 80% and 5 °C, 20 °C, or 30 °C indicated that both cold and dry conditions favor transmission. The relationship between transmission via aerosols and relative humidity at 20 °C is similar to that previously reported for the stability of influenza viruses (except at high relative humidity, 80%), implying that the effects of humidity act largely at the level of the virus particle. For infected guinea pigs housed at 5 °C, the duration of peak shedding was approximately 40 h longer than that of animals housed at 20 °C; this increased shedding likely accounts for the enhanced transmission seen at 5 °C. To investigate the mechanism permitting prolonged viral growth, expression levels in the upper respiratory tract of several innate immune mediators were determined. Innate responses proved to be comparable between animals housed at 5 °C and 20 °C, suggesting that cold temperature (5 °C) does not impair the innate immune response in this system. Although the seasonal epidemiology of influenza is well characterized, the underlying reasons for predominant wintertime spread are not clear. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution.
<!-- end abstract --> <!-- start footnote section -->Funding. This work was supported by grants from the W. M. Keck Foundation, the Centers for Disease Control R21 (U01CI000354–01), and the Center for Investigating Viral Immunity and Antagonism (1 UC19 AI062623–023) (to PP). ACL is a Parker B. Francis Fellow in Pulmonary Research. SM was supported by Sunnybrook Health Sciences Centre, Toronto, Canada, and a Ruth L. Kirschstein Physician Scientist Research Training in Pathogenesis of Viral Diseases Award (Mary Klotman, P.I.). PP is a senior fellow of the Ellison Medical Foundation.
Competing interests. The authors have declared that no competing interests exist.
Editor: Ralph S. Baric, University of North Carolina, United States of America
Citation: Lowen AC, Mubareka S, Steel J, Palese P (2007) Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature. PLoS Pathog 3(10): e151 doi:10.1371/journal.ppat.0030151
Received: July 11, 2007; Accepted: September 5, 2007; Published: October 19, 2007
Copyright: © 2007 Lowen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abbreviations: Ct, cycle threshold; p.i., post-inoculation; PFU, plaque-forming units; RH, relative humidity
* To whom correspondence should be addressed. E-mail: anice.lowen@mssm.edu (ACL), peter.palese@mssm.edu (PP)
<!-- end title area --> <!-- start authors --> http://pathogens.plosjournals.org/pe...l.ppat.0030151
Anice C. Lowen<sup>1</sup><sup>*</sup>, Samira Mubareka<sup>1</sup>, John Steel<sup>1</sup>, Peter Palese<sup>1,</sup><sup>2</sup><sup>*</sup>
<!-- end authors --><!-- start affiliations --> 1 Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America, 2 Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
<!-- end affiliations --><!-- start: abstract --> Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. Twenty experiments performed at relative humidities from 20% to 80% and 5 °C, 20 °C, or 30 °C indicated that both cold and dry conditions favor transmission. The relationship between transmission via aerosols and relative humidity at 20 °C is similar to that previously reported for the stability of influenza viruses (except at high relative humidity, 80%), implying that the effects of humidity act largely at the level of the virus particle. For infected guinea pigs housed at 5 °C, the duration of peak shedding was approximately 40 h longer than that of animals housed at 20 °C; this increased shedding likely accounts for the enhanced transmission seen at 5 °C. To investigate the mechanism permitting prolonged viral growth, expression levels in the upper respiratory tract of several innate immune mediators were determined. Innate responses proved to be comparable between animals housed at 5 °C and 20 °C, suggesting that cold temperature (5 °C) does not impair the innate immune response in this system. Although the seasonal epidemiology of influenza is well characterized, the underlying reasons for predominant wintertime spread are not clear. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution.
<!-- end abstract --> <!-- start footnote section -->Funding. This work was supported by grants from the W. M. Keck Foundation, the Centers for Disease Control R21 (U01CI000354–01), and the Center for Investigating Viral Immunity and Antagonism (1 UC19 AI062623–023) (to PP). ACL is a Parker B. Francis Fellow in Pulmonary Research. SM was supported by Sunnybrook Health Sciences Centre, Toronto, Canada, and a Ruth L. Kirschstein Physician Scientist Research Training in Pathogenesis of Viral Diseases Award (Mary Klotman, P.I.). PP is a senior fellow of the Ellison Medical Foundation.
Competing interests. The authors have declared that no competing interests exist.
Editor: Ralph S. Baric, University of North Carolina, United States of America
Citation: Lowen AC, Mubareka S, Steel J, Palese P (2007) Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature. PLoS Pathog 3(10): e151 doi:10.1371/journal.ppat.0030151
Received: July 11, 2007; Accepted: September 5, 2007; Published: October 19, 2007
Copyright: © 2007 Lowen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abbreviations: Ct, cycle threshold; p.i., post-inoculation; PFU, plaque-forming units; RH, relative humidity
* To whom correspondence should be addressed. E-mail: anice.lowen@mssm.edu (ACL), peter.palese@mssm.edu (PP)
Comment