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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

Influenza virus detection in aerosol samples exhaled by infected ferrets.Three ferrets each were housed under the designated environmental conditions and were presented with 103.8–105.5 pfu of PN99 (green) or IN11 (orange) virus by aerosol inhalation. On 1, 3 and 5 dpi, aerosol samples were collected from ferrets for 15 minutes of normal breathing (A) and 5 minutes of sneezing stimulation (B) and were segregated based on size (0.65–4.7 μm or >4.7 μm) and then assayed for the presence of infectious influenza virus. Total plaque forming units (pfu) from individual ferrets, n = 3, is shown with the grand mean for each sampling condition.
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pone.0125874.g005: Influenza virus detection in aerosol samples exhaled by infected ferrets.Three ferrets each were housed under the designated environmental conditions and were presented with 103.8–105.5 pfu of PN99 (green) or IN11 (orange) virus by aerosol inhalation. On 1, 3 and 5 dpi, aerosol samples were collected from ferrets for 15 minutes of normal breathing (A) and 5 minutes of sneezing stimulation (B) and were segregated based on size (0.65–4.7 μm or >4.7 μm) and then assayed for the presence of infectious influenza virus. Total plaque forming units (pfu) from individual ferrets, n = 3, is shown with the grand mean for each sampling condition.

Mentions: Any successful aerosol transmission event requires that infectious virus pass through the air from a contagious host to a susceptible one. Using methods designed to maintain the viability of infectious virus in aerosols, sampling of the exhaled breath of ferrets was performed and comparisons were made among the amounts of infectious virus exhaled by influenza virus infected ferrets housed under the controlled environmental conditions. Aerosols were collected for 15 minutes of normal breathing and 5 minutes of sneezing and separated into two size ranges (>4.7 μm and 0.65–4.7 μm) on 1, 3 and 5 dpi and then quantified for influenza virus by plaque assay as well as real-time RT-PCR. Infectious virus detected at any time point and in either size range in normal breathing samples was ≤10 pfu (Fig 5A) and in sneezing samples was ≤34 pfu (Fig 5B). The overall normal breathing grand mean values were lowest at 23°C/50%RH (Fig 5A) while other conditions were similar but slightly higher, and little difference was observed between the two size ranges (<4.7 μm and ≥4.7 μm). With few exceptions, the levels of IN11 virus measured were higher compared to PN99 virus at the respective housing conditions, similar to NW titer comparison results (Fig 2). Likewise, in most cases, IN11 virus RNA levels were higher in these samples compared to PN99 virus. This was most evident in the higher humidity conditions during normal breathing (Fig 6A) and nearly all of the sneezing samples (Fig 6B).


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)

Influenza virus detection in aerosol samples exhaled by infected ferrets.Three ferrets each were housed under the designated environmental conditions and were presented with 103.8–105.5 pfu of PN99 (green) or IN11 (orange) virus by aerosol inhalation. On 1, 3 and 5 dpi, aerosol samples were collected from ferrets for 15 minutes of normal breathing (A) and 5 minutes of sneezing stimulation (B) and were segregated based on size (0.65–4.7 μm or >4.7 μm) and then assayed for the presence of infectious influenza virus. Total plaque forming units (pfu) from individual ferrets, n = 3, is shown with the grand mean for each sampling condition.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0125874.g005: Influenza virus detection in aerosol samples exhaled by infected ferrets.Three ferrets each were housed under the designated environmental conditions and were presented with 103.8–105.5 pfu of PN99 (green) or IN11 (orange) virus by aerosol inhalation. On 1, 3 and 5 dpi, aerosol samples were collected from ferrets for 15 minutes of normal breathing (A) and 5 minutes of sneezing stimulation (B) and were segregated based on size (0.65–4.7 μm or >4.7 μm) and then assayed for the presence of infectious influenza virus. Total plaque forming units (pfu) from individual ferrets, n = 3, is shown with the grand mean for each sampling condition.
Mentions: Any successful aerosol transmission event requires that infectious virus pass through the air from a contagious host to a susceptible one. Using methods designed to maintain the viability of infectious virus in aerosols, sampling of the exhaled breath of ferrets was performed and comparisons were made among the amounts of infectious virus exhaled by influenza virus infected ferrets housed under the controlled environmental conditions. Aerosols were collected for 15 minutes of normal breathing and 5 minutes of sneezing and separated into two size ranges (>4.7 μm and 0.65–4.7 μm) on 1, 3 and 5 dpi and then quantified for influenza virus by plaque assay as well as real-time RT-PCR. Infectious virus detected at any time point and in either size range in normal breathing samples was ≤10 pfu (Fig 5A) and in sneezing samples was ≤34 pfu (Fig 5B). The overall normal breathing grand mean values were lowest at 23°C/50%RH (Fig 5A) while other conditions were similar but slightly higher, and little difference was observed between the two size ranges (<4.7 μm and ≥4.7 μm). With few exceptions, the levels of IN11 virus measured were higher compared to PN99 virus at the respective housing conditions, similar to NW titer comparison results (Fig 2). Likewise, in most cases, IN11 virus RNA levels were higher in these samples compared to PN99 virus. This was most evident in the higher humidity conditions during normal breathing (Fig 6A) and nearly all of the sneezing samples (Fig 6B).

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