Predictors of indoor absolute humidity and estimated effects on influenza virus survival in grade schools

BMC Infectious Diseases

W Charles Huskins⁶  Jeffrey Shaman³  Marc Lipsitch²  Kevin L Neff⁵  Dale Krageschmidt⁴  Stephen C Ekker⁵  Chris Pierret⁵  Felicity T Enders¹  Tyler H Koep⁷ 

[1]Department of Health Sciences Research, Mayo Clinic, Rochester, MN, 55905, USA

[2]Center for Communicable Disease Dynamics, Department of Epidemiology and Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA, 02115, USA

[3]Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY, 10032, USA

[4]Department of Facilities and Support Services, Mayo Clinic, Rochester, MN, 55905, USA

[5]Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, 55905, USA

[6]Division of Pediatric Infectious Diseases, Department of Pediatric and Adolescent Medicine, Mayo Clinic Children’s Center, Rochester, MN, 55905, USA

[7]Clinical and Translational Sciences, Mayo Graduate School, Mayo Clinic, Rochester, MN, 55905, USA

关键词: Climate;    Schools;    Humidity;    Influenza;   

Others  :  1158434
DOI  :  10.1186/1471-2334-13-71

 received in 2012-11-13, accepted in 2013-01-29,  发布年份 2013

【 摘 要 】

Background

Low absolute humidity (AH) has been associated with increased influenza virus survival and transmissibility and the onset of seasonal influenza outbreaks. Humidification of indoor environments may mitigate viral transmission and may be an important control strategy, particularly in schools where viral transmission is common and contributes to the spread of influenza in communities. However, the variability and predictors of AH in the indoor school environment and the feasibility of classroom humidification to levels that could decrease viral survival have not been studied.

Methods

Automated sensors were used to measure temperature, humidity and CO₂ levels in two Minnesota grade schools without central humidification during two successive winters. Outdoor AH measurements were derived from the North American Land Data Assimilation System. Variability in indoor AH within classrooms, between classrooms in the same school, and between schools was assessed using concordance correlation coefficients (CCC). Predictors of indoor AH were examined using time-series Auto-Regressive Conditional Heteroskedasticity models. Classroom humidifiers were used when school was not in session to assess the feasibility of increasing indoor AH to levels associated with decreased influenza virus survival, as projected from previously published animal experiments.

Results

AH varied little within classrooms (CCC >0.90) but was more variable between classrooms in the same school (CCC 0.81 for School 1, 0.88 for School 2) and between schools (CCC 0.81). Indoor AH varied widely during the winter (range 2.60 to 10.34 millibars [mb]) and was strongly associated with changes in outdoor AH (p < 0.001). Changes in indoor AH on school weekdays were strongly associated with CO₂ levels (p < 0.001). Over 4 hours, classroom humidifiers increased indoor AH by 4 mb, an increase sufficient to decrease projected 1-hour virus survival by an absolute value of 30% during winter months.

Conclusions

During winter, indoor AH in non-humidified grade schools varies substantially and often to levels that are very low. Indoor results are predicted by outdoor AH over a season and CO₂ levels (which likely reflects human activity) during individual school days. Classroom humidification may be a feasible approach to increase indoor AH to levels that may decrease influenza virus survival and transmission.

【 授权许可】

   
2013 Koep et al.; licensee BioMed Central Ltd.

【 图 表 】

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