Airborne influenza virus detection with four aerosol samplers using molecular and infectivity assays: considerations for a new infectious virus aerosol sampler

Abstract

As a first step in conducting studies of airborne influenza transmission, we compared the collection performance of an SKC Biosampler, a compact cascade impactor (CCI), Teflon filters, and gelatin filters by collecting aerosolized influenza virus in a one-pass aerosol chamber. Influenza virus infectivity was determined using a fluorescent focus assay and influenza virus nucleic acid (originating from viable and non-viable viruses) was measured using quantitative PCR. The results showed that the SKC Biosampler recovered and preserved influenza virus infectivity much better than the other samplers - the CCI, Teflon, and gelatin filters recovered only 7-22% of infectious viruses compared with the Biosampler. Total virus collection was not significantly different among the SKC Biosampler, the gelatin, and Teflon filters, but was significantly lower in the CCI. Results from this study show that a new sampler is needed for virus aerosol sampling, as commercially available samplers do not efficiently collect and conserve virus infectivity. Applications for a new sampler include studies of airborne disease transmission and bioterrorism monitoring. Design parameters for a new sampler include high collection efficiency for fine particles and liquid sampling media to preserve infectivity. Practical Implications New air samplers are needed to study infectious airborne viruses and learn about airborne disease transmission. As a first step in designing a new air sampler to collect influenza virus we evaluated four commercial samplers and determined necessary design parameters for a new collector.

Fig. 1

Diagram of the one-pass experimental system used to aerosolize and collect influenza viruses

Fig. 2

Infectious influenza virus recovered from aerosol samplers, quantified by culture (n = 18 [3 samples × 2 experiments × 3 wells]). Mean concentrations estimated from mixed regression model and controlled for experiment number, time and correlation among focus assay wells. Error bars indicate 95% confidence intervals.

Fig. 3

Total influenza virus RNA measured from aerosol samplers, quantified by qPCR (n = 18 [3 samples × 2 experiments × 3 wells]). Mean concentrations estimated from a mixed regression model and controlled for experiment number, time and correlation among focus assay wells. Error bars indicate 95% confidence intervals.