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Environmental Conditions Affect Exhalation of H3N2 Seasonal and Variant Influenza Viruses and Respiratory Droplet Transmission in Ferrets.

Gustin KM, Belser JA, Veguilla V, Zeng H, Katz JM, Tumpey TM, Maines TR - PLoS ONE (2015)

Bottom Line: We report here that although increased levels of H3N2 variant virus were found in ferret nasal wash and exhaled aerosol samples compared to the seasonal H3N2 virus, enhanced respiratory droplet transmission was not observed under any of the environmental settings.Transmission occurred most frequently at 23°C/30%RH, while the levels of infectious virus in aerosols exhaled by infected ferrets agree with these results.Improving our understanding of how environmental conditions affect influenza virus infectivity and transmission may reveal ways to better protect the public against influenza virus infections.

View Article: PubMed Central - PubMed

Affiliation: Influenza Division, National Center for Immunization and Respiratory Disease, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.

ABSTRACT
The seasonality of influenza virus infections in temperate climates and the role of environmental conditions like temperature and humidity in the transmission of influenza virus through the air are not well understood. Using ferrets housed at four different environmental conditions, we evaluated the respiratory droplet transmission of two influenza viruses (a seasonal H3N2 virus and an H3N2 variant virus, the etiologic virus of a swine to human summertime infection) and concurrently characterized the aerosol shedding profiles of infected animals. Comparisons were made among the different temperature and humidity conditions and between the two viruses to determine if the H3N2 variant virus exhibited enhanced capabilities that may have contributed to the infections occurring in the summer. We report here that although increased levels of H3N2 variant virus were found in ferret nasal wash and exhaled aerosol samples compared to the seasonal H3N2 virus, enhanced respiratory droplet transmission was not observed under any of the environmental settings. However, overall environmental conditions were shown to modulate the frequency of influenza virus transmission through the air. Transmission occurred most frequently at 23°C/30%RH, while the levels of infectious virus in aerosols exhaled by infected ferrets agree with these results. Improving our understanding of how environmental conditions affect influenza virus infectivity and transmission may reveal ways to better protect the public against influenza virus infections.

No MeSH data available.


Related in: MedlinePlus

Size distribution of aerosols exhaled from influenza virus infected ferrets.Aerosol particle counts were measured for individual ferrets, n = 3, collected during 15 minutes of normal breathing (A) or 5 minutes of sneezing stimulation (B) on 2, 4 and 6 dpi. Ferrets were housed under controlled environmental conditions as indicated. Aerosol particles within the range of 0.5μm to 20 μm in size are shown with key sizes noted on the x axis and a broken vertical line denoting the respirable particle fraction at <5 μm.
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pone.0125874.g003: Size distribution of aerosols exhaled from influenza virus infected ferrets.Aerosol particle counts were measured for individual ferrets, n = 3, collected during 15 minutes of normal breathing (A) or 5 minutes of sneezing stimulation (B) on 2, 4 and 6 dpi. Ferrets were housed under controlled environmental conditions as indicated. Aerosol particles within the range of 0.5μm to 20 μm in size are shown with key sizes noted on the x axis and a broken vertical line denoting the respirable particle fraction at <5 μm.

Mentions: Respiratory secretions exhaled into the air serve as the vehicle for influenza viruses to transmit between hosts in the absence of direct or indirect contact. To assess the effects of temperature and humidity on the size distribution of aerosols exhaled from ferrets infected by PN99 or IN11 virus, an APS was used to measure the aerodynamic diameter of particles present in aerosol samples collected on 2, 4 and 6 dpi from ferrets housed at each controlled environmental condition. Aerosol particle counts in exhaled breath were highly variable among ferrets but, for all animals, peaked in the respirable size range (Fig 3). During 15 minutes of normal breathing, aerosol particle counts were highest 4 dpi; significance at this time point was found among all ferret groups (p<0.0001) except PN99 virus at 5°C/70%RH and IN11 virus at 23°C/30%RH (Fig 3A). Overall, particle counts were lowest at the lowest RH condition (23°C/30%RH) (p<0.0001) which is probably because a greater proportion of the aerosol particles are <0.5 μm, below the detection limit of the APS, due to evaporation. During 5 minutes of sneezing stimulation, much more variability was observed between ferrets and between conditions (Fig 3B). Because aerosols were collected for size distribution analysis on days 2, 4 and 6 post-inoculation and nasal wash samples were collected on days 1, 3 and 5 post-inoculation, the kinetics of increased aerosol shedding cannot be linked to the time point at which transmission was observed for each animal. In fact, the highest numbers of aerosol particle counts were measured during normal breathing on 4 dpi in the IN11 virus group housed at 5C/70%RH (Fig 3A) and no transmission was observed in these animals (Fig 2B, Table 1). Particle counts in sneezing samples were highest at 23C/70%RH for both virus groups but transmission occurred among 67% of ferret pairs at this setting.


Environmental Conditions Affect Exhalation of H3N2 Seasonal and Variant Influenza Viruses and Respiratory Droplet Transmission in Ferrets.

Gustin KM, Belser JA, Veguilla V, Zeng H, Katz JM, Tumpey TM, Maines TR - PLoS ONE (2015)

Size distribution of aerosols exhaled from influenza virus infected ferrets.Aerosol particle counts were measured for individual ferrets, n = 3, collected during 15 minutes of normal breathing (A) or 5 minutes of sneezing stimulation (B) on 2, 4 and 6 dpi. Ferrets were housed under controlled environmental conditions as indicated. Aerosol particles within the range of 0.5μm to 20 μm in size are shown with key sizes noted on the x axis and a broken vertical line denoting the respirable particle fraction at <5 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430532&req=5

pone.0125874.g003: Size distribution of aerosols exhaled from influenza virus infected ferrets.Aerosol particle counts were measured for individual ferrets, n = 3, collected during 15 minutes of normal breathing (A) or 5 minutes of sneezing stimulation (B) on 2, 4 and 6 dpi. Ferrets were housed under controlled environmental conditions as indicated. Aerosol particles within the range of 0.5μm to 20 μm in size are shown with key sizes noted on the x axis and a broken vertical line denoting the respirable particle fraction at <5 μm.
Mentions: Respiratory secretions exhaled into the air serve as the vehicle for influenza viruses to transmit between hosts in the absence of direct or indirect contact. To assess the effects of temperature and humidity on the size distribution of aerosols exhaled from ferrets infected by PN99 or IN11 virus, an APS was used to measure the aerodynamic diameter of particles present in aerosol samples collected on 2, 4 and 6 dpi from ferrets housed at each controlled environmental condition. Aerosol particle counts in exhaled breath were highly variable among ferrets but, for all animals, peaked in the respirable size range (Fig 3). During 15 minutes of normal breathing, aerosol particle counts were highest 4 dpi; significance at this time point was found among all ferret groups (p<0.0001) except PN99 virus at 5°C/70%RH and IN11 virus at 23°C/30%RH (Fig 3A). Overall, particle counts were lowest at the lowest RH condition (23°C/30%RH) (p<0.0001) which is probably because a greater proportion of the aerosol particles are <0.5 μm, below the detection limit of the APS, due to evaporation. During 5 minutes of sneezing stimulation, much more variability was observed between ferrets and between conditions (Fig 3B). Because aerosols were collected for size distribution analysis on days 2, 4 and 6 post-inoculation and nasal wash samples were collected on days 1, 3 and 5 post-inoculation, the kinetics of increased aerosol shedding cannot be linked to the time point at which transmission was observed for each animal. In fact, the highest numbers of aerosol particle counts were measured during normal breathing on 4 dpi in the IN11 virus group housed at 5C/70%RH (Fig 3A) and no transmission was observed in these animals (Fig 2B, Table 1). Particle counts in sneezing samples were highest at 23C/70%RH for both virus groups but transmission occurred among 67% of ferret pairs at this setting.

Bottom Line: We report here that although increased levels of H3N2 variant virus were found in ferret nasal wash and exhaled aerosol samples compared to the seasonal H3N2 virus, enhanced respiratory droplet transmission was not observed under any of the environmental settings.Transmission occurred most frequently at 23°C/30%RH, while the levels of infectious virus in aerosols exhaled by infected ferrets agree with these results.Improving our understanding of how environmental conditions affect influenza virus infectivity and transmission may reveal ways to better protect the public against influenza virus infections.

View Article: PubMed Central - PubMed

Affiliation: Influenza Division, National Center for Immunization and Respiratory Disease, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.

ABSTRACT
The seasonality of influenza virus infections in temperate climates and the role of environmental conditions like temperature and humidity in the transmission of influenza virus through the air are not well understood. Using ferrets housed at four different environmental conditions, we evaluated the respiratory droplet transmission of two influenza viruses (a seasonal H3N2 virus and an H3N2 variant virus, the etiologic virus of a swine to human summertime infection) and concurrently characterized the aerosol shedding profiles of infected animals. Comparisons were made among the different temperature and humidity conditions and between the two viruses to determine if the H3N2 variant virus exhibited enhanced capabilities that may have contributed to the infections occurring in the summer. We report here that although increased levels of H3N2 variant virus were found in ferret nasal wash and exhaled aerosol samples compared to the seasonal H3N2 virus, enhanced respiratory droplet transmission was not observed under any of the environmental settings. However, overall environmental conditions were shown to modulate the frequency of influenza virus transmission through the air. Transmission occurred most frequently at 23°C/30%RH, while the levels of infectious virus in aerosols exhaled by infected ferrets agree with these results. Improving our understanding of how environmental conditions affect influenza virus infectivity and transmission may reveal ways to better protect the public against influenza virus infections.

No MeSH data available.


Related in: MedlinePlus