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. 2013 Jun 22:10:204.
doi: 10.1186/1743-422X-10-204.

Airborne spread and infection of a novel swine-origin influenza A (H1N1) virus

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Airborne spread and infection of a novel swine-origin influenza A (H1N1) virus

Hongna Zhang et al. Virol J. .

Abstract

Background: The novel swine-origin influenza A (H1N1) virus (S-O 2009 IV) can cause respiratory infectious diseases in humans and pigs, but there are few studies investigating the airborne spread of the virus. In January 2011, a swine-origin H1N1 epidemic emerged in eastern China that rapidly spread to neighboring farms, likely by aerosols carried by the wind.

Methods: In this study, quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to detect viruses in air samples from pig farms. Based on two aerosol infection models (Pig and guinea pig), we evaluated aerosol transmission and infection of the novel S-O 2009 IV isolate.

Results: Three novel S-O 2009 IV were isolated from the diseased pig. The positive rate and viral loads of air samples were 26.1% and 3.14-5.72 log₁₀copies/m³ air, respectively. In both pig and guinea pig infection models, the isolate (A/swine/Shandong/07/2011) was capable of forming aerosols and infected experimental animals at a range of 2.0-4.2 m by aerosols, but aerosol route was less efficient than direct contact.

Conclusions: The results indicated that S-O 2009 IV is able to be aerosolized by infected animals and to be transmitted to susceptible animals by airborne routes.

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Figures

Figure 1
Figure 1
Concentration of the SO 2009(H1N1)IV aerosol produced by pigs and guinea pigs in isolators A and B. The diamond represents the first round of experiment; triangle represents the second. Black represents isolator A, white represents isolator B. (B) Not detected in the first round of experiment 4dpi Day 0: animals in group A w ere intranasally inoculated with 106 pfu of the novel influenza A (H1N1) virus.
Figure 2
Figure 2
Distribution characteristics of the novel influenza A (H1N1) virus from isolator A and B on the Andersen-8-stage impactor, Based on RT-qPCR results. X-axis: aerodynamic diameter of airborne viral particles on Andersen-8 sampler (from left to right:1-8 stage); Y-axis: the distribution percentage of viral particles on every stage of Andersen-8 sampler.
Figure 3
Figure 3
The map is the part of East China area, red points represent the positive pig farms, and yellow ones represent the negative pig farms.
Figure 4
Figure 4
Arrangement of the isolators applicable to pigs and guinea pigs. Animals in inoculation group (GA) and direct contact group (GB) were housed in the isolator A, and animals in aerosol infection group (GC) were housed in the isolator B. The two isolators were connected with a tube(2 m) which allowed the air flowed from A to B. SH is a sampling hole from which air samples were collected. F1 is a positive pressure fan and F2 is a negative fan. The air flowing through the two fans was filtered to remove microorganisms.

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