Concentration, Size Distribution, and Infectivity of Airborne Particles Carrying Swine Viruses.
When pathogens become airborne, they travel associated with particles of different size and composition. Particle size determines the distance across which pathogens can be transported, as well as the site of deposition and the survivability of the pathogen. Despite the importance of this information, the size distribution of particles bearing viruses emitted by infectious animals remains unknown. In this study we characterized the concentration and size distribution of inhalable particles that transport influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine epidemic diarrhea virus (PEDV) generated by acutely infected pigs and assessed virus viability for each particle size range. Aerosols from experimentally infected pigs were sampled for 24 days using an Andersen cascade impactor able to separate particles by size (ranging from 0.4 to 10 micrometer (μm) in diameter). Air samples collected for the first 9, 20 and the last 3 days of the study were analyzed for IAV, PRRSV and PEDV, respectively, using quantitative reverse transcription polymerase chain reaction (RT-PCR) and quantified as geometric mean copies/m(3) within each size range. IAV was detected in all particle size ranges in quantities ranging from 5.5x10(2) (in particles ranging from 1.1 to 2.1 μm) to 4.3x10(5) RNA copies/m(3) in the largest particles (9.0-10.0 μm). PRRSV was detected in all size ranges except particles between 0.7 and 2.1 μm in quantities ranging from 6x10(2) (0.4-0.7 μm) to 5.1x10(4) RNA copies/m(3) (9.0-10.0 μm). PEDV, an enteric virus, was detected in all particle sizes and in higher quantities than IAV and PRRSV (p < 0.0001) ranging from 1.3x10(6) (0.4-0.7 μm) to 3.5x10(8) RNA copies/m(3) (9.0-10.0 μm). Infectious status was demonstrated for the 3 viruses, and in the case of IAV and PRRSV, viruses were isolated from particles larger than 2.1 μm. In summary, our results indicated that airborne PEDV, IAV and PRRSV can be found in a wide range of particle sizes. However, virus viability is particle size dependent.
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota-Twin Cities, Saint Paul, Minnesota, United States of America.
Carmen
C
Alonso
Division of Environmental Health Sciences, School of Public Health, University of Minnesota-Twin Cities, Saint Paul, Minnesota, United States of America.
Peter C
PC
Raynor
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota-Twin Cities, Saint Paul, Minnesota, United States of America.
Peter R
PR
Davies
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota-Twin Cities, Saint Paul, Minnesota, United States of America.
Montserrat
M
Torremorell
D000336:Aerosols; D000391:Air Microbiology; D000818:Animals; D018352:Coronavirus Infections / Q000635:transmission / Q000821:virology; D009980:Influenza A virus / Q000302:isolation & purification*; D050296:Microbial Viability; D009976:Orthomyxoviridae Infections / Q000635:transmission / Q000821:virology; D010316:Particle Size; D052638:Particulate Matter / Q000009:adverse effects*; D019318:Porcine Reproductive and Respiratory Syndrome / Q000635:transmission / Q000821:virology; D053485:Porcine epidemic diarrhea virus / Q000302:isolation & purification*; D019316:Porcine respiratory and reproductive syndrome virus / Q000302:isolation & purification*; D012367:RNA, Viral / Q000235:genetics; D013552:Swine; D013553:Swine Diseases / Q000821:virology; D019562:Viral Load
D000336:Aerosols; D052638:Particulate Matter; D012367:RNA, Viral