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Relative contributions of four exposure pathways to influenza infection risk.

Authors
Nicas-M; Jones-RM
Source
Risk Anal 2009 Sep; 29(9):1292-1303
NIOSHTIC No.
20037357
Abstract
The relative contribution of four influenza virus exposure pathways--(1) virus-contaminated hand contact with facial membranes, (2) inhalation of respirable cough particles, (3) inhalation of inspirable cough particles, and (4) spray of cough droplets onto facial membranes--must be quantified to determine the potential efficacy of nonpharmaceutical interventions of transmission. We used a mathematical model to estimate the relative contributions of the four pathways to infection risk in the context of a person attending a bed-ridden family member ill with influenza. Considering the uncertainties in the sparse human subject influenza dose-response data, we assumed alternative ratios of 3,200:1 and 1:1 for the infectivity of inhaled respirable virus to intranasally instilled virus. For the 3,200:1 ratio, pathways (1), (2), and (4) contribute substantially to influenza risk: at a virus saliva concentration of 106 mL-1, pathways (1), (2), (3), and (4) contribute, respectively, 31%, 17%, 0.52%, and 52% of the infection risk. With increasing virus concentrations, pathway (2) increases in importance, while pathway (4) decreases in importance. In contrast, for the 1:1 infectivity ratio, pathway (1) is the most important overall: at a virus saliva concentration of 106 mL-1, pathways (1), (2), (3), and (4) contribute, respectively, 93%, 0.037%, 3.3%, and 3.7% of the infection risk.With increasing virus concentrations, pathway (3) increases in importance, while pathway (4) decreases in importance. Given the sparse knowledge concerning influenza dose and infectivity via different exposure pathways, nonpharmaceutical interventions for influenza should simultaneously address potential exposure via hand contact to the face, inhalation, and droplet spray.
Keywords
Aerosol-particles; Aerosols; Airborne-particles; Air-contamination; Bacterial-dusts; Bacterial-infections; Biological-effects; Biological-function; Cell-biology; Environmental-contamination; Environmental-exposure; Exposure-assessment; Exposure-levels; Exposure-methods; Health-hazards; Health-standards; Immune-reaction; Immune-system; Inhalants; Inhalation-studies; Laboratory-testing; Mathematical-models; Pollutants; Quantitative-analysis; Risk-analysis; Risk-factors; Statistical-analysis; Surface-properties; Author Keywords: Influenza; microbial risk assessment; transmission pathway
Contact
Mark Nicas, Room 50, University Hall, School of Public Health,University of California, Berkeley, Berkeley, CA 94720-7360
CODEN
RIANDF
Publication Date
20090901
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
2009
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-T42-OH-008429; Contract-211-2006-M-16790; Contract-211-2006-M-16255
Issue of Publication
9
ISSN
0272-4332
Source Name
Risk Analysis
State
CA
Performing Organization
University of California, Berkeley
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