Major article
A pandemic influenza preparedness study: Use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets

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Background

A major concern among health care experts is a projected shortage of N95 filtering facepiece respirators (FFRs) during an influenza pandemic. One option for mitigating an FFR shortage is to decontaminate and reuse the devices. Many parameters, including biocidal efficacy, filtration performance, pressure drop, fit, and residual toxicity, must be evaluated to verify the effectiveness of this strategy. The focus of this research effort was on evaluating the ability of microwave-generated steam, warm moist heat, and ultraviolet germicidal irradiation at 254 nm to decontaminate H1N1 influenza virus.

Methods

Six commercially available FFR models were contaminated with H1N1 influenza virus as aerosols or droplets that are representative of human respiratory secretions. A subset of the FFRs was treated with the aforementioned decontamination technologies, whereas the remaining FFRs were used to evaluate the H1N1 challenge applied to the devices.

Results

All 3 decontamination technologies provided >4-log reduction of viable H1N1 virus. In 93% of our experiments, the virus was reduced to levels below the limit of detection of the method used.

Conclusions

These data are encouraging and may contribute to the evolution of effective strategies for the decontamination and reuse of FFRs.

Section snippets

Preparation of H1N1 virus

Influenza A/PR/8/34 VR-1469 (ATCC VR-95H1N1) was propagated in embryonic chicken eggs following standard protocols.37 Virus titers were determined using a tissue culture infectious dose assay (TCID50) in Madin–Darby canine kidney cells (MDCK; ATCC CCL-34) with WHO-approved cell culture techniques.37

Aerosol application of H1N1 to FFRs

The laboratory-scale aerosol tunnel (LSAT; Fig 2) was used to apply H1N1 aerosols to the 6 FFR models (3 particulate, designated P1-P3, and 3 surgical, designated S1-S3). The LSAT was designed to

Results

The average concentration of H1N1 virus recovered from the untreated FFRs for each test ranged from 4.1 to 6.1 log10 TCID50 per sample (Table 1). The variability is a result of day-to-day deviation in testing and does not reflect the overall consistency of the method. The average SD for the triplicate untreated samples for all 36 tests was 0.27 log10TCID50, similar to that reported by others.43 All 3 energetic methods provided an average >4-log reduction of viable H1N1 influenza virus against

Discussion

A unique feature of the present study is the controlled contamination of FFRs with H1N1 influenza using aerosol methods, which provide a radically different challenge from solution-based tests, which require dilution of the virus in a large volume of water. As droplets form during aerosolization, they begin to dry and form droplet nuclei. As evaporation proceeds, viruses are coated with protective components from the aerosolization medium; these components can protect the virus from some

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    Conflict of interest: None to report.

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