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workers, building, architect

NORA Manufacturing Sector Strategic Goals

R019288 - 021H: Measurement of Particle Sizes Associated with Airborne Viruses (9288)

Start Date: 9/1/2008
End Date: 8/31/2012

Principal Investigator (PI)
Name: Joan Karr
Organization: NIOSH
Sub-Unit: OEP
Funded By: NIOSH

Primary Goal Addressed

Secondary Goal Addressed


Attributed to Manufacturing


Project Description

Short Summary

The objectives of the proposed research are to develop and validate a method to determine virus concentration in air as a function of particle size, to use the method to measure the particle sizes with which airborne viruses are associated in occupational settings, and to begin to assess the effectiveness of control measures for viral aerosols as a function of particle size. To achieve the research objectives, systematic laboratory and field studies will be applied.


Health care personnel, swine and poultry farm workers, airline and public transportation workers, and others may be infected by a variety of viruses that can be transmitted through air. Infection control experts divide transmission of infectious agents through air into two categories, e.g., “droplet transmission” and “airborne transmission”. Conventional wisdom suggests that most transmission of infectious viruses occurs by droplet transmission. However, more recent research indicates that at least some viruses can be transmitted by the airborne route. Remarkably, no one has assessed the sizes of particles with which viruses are associated in occupational environments. Our research will answer this critical question: 'Is airborne viral transmission a more important mechanism than conventional wisdom suggests?” During this study, methods will be developed to quantify the amount of virus associated with airborne particles of different sizes and the viability of these viruses in any environment. The first step is to separate airborne particles into different size ranges. Impactors and differential mobility analyzers will be evaluated for their ability to achieve this separation. The second step is to analyze the particles divided into each size range for the amount of virus present within them. The quantification of live viruses (and a bacteriophage) will be accomplished by inoculation of appropriate cell systems (or bacterial host for bacteriophage). Molecular methods such as polymerase chain reaction (PCR) will also be used as a semiquantitative method to detect both live and inactivated viruses. After methods are validated in the laboratory, they will be used in swine barns and health care facilities to measure particle sizes with which viable and non-viable viruses are associated and to which workers may be exposed. This improved understanding of virus behavior will influence the procedures and technology used to prevent virus transmission in health care facilities, animal facilities, public venues, and other workplaces.


The specific aims of the proposed research are:

(1) For six test viruses, develop a method of generating consistent virus test aerosols that simulate viral aerosols generated by sneezing or coughing.

(2) Use the test aerosols to develop and evaluate an aerosol impactor system as a way to sample viral aerosols size-selectively.

(3) Use the test aerosols to develop and evaluate a Differential Mobility Analyzer (DMA) sampling system as a way to size-selectively sample viral aerosols.

(4) For size-segregated samples, evaluate the ability of conventional virus isolation techniques to efficiently detect and quantify viable test viruses by isolation and titration

in a susceptible host system.

(5) For size-segregated samples, evaluate molecular techniques (PCR and RT-PCR) to detect and quantify the test viruses.

(6) Validate the most promising sampling systems developed in aims 2 and 3 and the virus analysis methods developed in aims 4 and 5 by measuring the size-by-size

concentrations of laboratory-generated viral test aerosols in an 'initial test apparatus' and in an environmental chamber.

(7) Using the environmental chamber, measure the influence that changes in temperature and humidity have on particle sizes with which test viruses are associated and the

viability of those viruses.

(8) Using the environmental chamber, measure the potential for test viruses settled on surfaces to be resuspended and to contribute to the viable virus content in the air.

(9) Evaluate the effectiveness of heating, ventilating, and air-conditioning (HVAC) filters at collecting viral aerosol particles in the environmental chamber.

(10) Evaluate the effectiveness of ultraviolet germicidal irradiation (UVGI) units at inactivating viral aerosol particles in the environmental chamber.

(11) Use the methods developed in the laboratory to measure size-by-size concentrations of swine influenza virus (SIV) and porcine reproductive and respiratory syndrome virus (PRRSV) in the air of swine barns.

(12) Use the methods developed in the laboratory to measure size-by-size human influenza virus concentrations in the air of health care facilities.