scholarly journals Superspreading Events Without Superspreaders: Using High Attack Rate Events to Estimate Nº for Airborne Transmission of COVID-19

2020 ◽  
Author(s):  
Mara Prentiss ◽  
Arthur Chu ◽  
Karl K. Berggren
Keyword(s):  
Call Center ◽  
Influenza A ◽  
Characteristic Number ◽  
Symptomatic Patient ◽  
Airborne Transmission ◽  
Viral Loads ◽  
Simple Physical Model ◽  
Exercise Class ◽  
Poor Ventilation ◽  
Large Groups

AbstractWe study transmission of COVID-19 using five well-documented case studies – a Washington state church choir, a Korean call center, a Korean exercise class, and two different Chinese bus trips. In all cases the likely index patients were pre-symptomatic or mildly symptomatic, which is when infective patients are most likely to interact with large groups of people. An estimate of N0, the characteristic number of COVID-19 virions needed to induce infection in each case, is found using a simple physical model of airborne transmission. We find that the N0 values are similar for five COVID-19 superspreading cases (∼300-2,000 viral copies) and of the same order as influenza A. Consistent with the recent results of Goyal et al, these results suggest that viral loads relevant to infection from presymptomatic or mildly symptomatic individuals may fall into a narrow range, and that exceptionally high viral loads are not required to induce a superspreading event [1,2]. Rather, the accumulation of infective aerosols exhaled by a typical pre-symptomatic or mildly symptomatic patient in a confined, crowded space (amplified by poor ventilation, particularly activity like exercise or singing, or lack of masks) for exposure times as short as one hour are sufficient. We calculate that talking and breathing release ∼460N0 and ∼10N0 (quanta)/hour, respectively, providing a basis to estimate the risks of everyday activities. Finally, we provide a calculation which motivates the observation that fomites appear to account for a small percentage of total COVID-19 infection events.

scholarly journals Higher Viral Load and Prolonged Viral Shedding Period is Associated with Impaired Th17 Cell Response in Patients with H1N1 Influenza A

2012 ◽  
Vol 1 (3) ◽  
pp. 137-145
Author(s):  
Gui-lin Yang ◽  
Ying-xia Liu ◽  
Mu-tong Fang ◽  
Wei-long Liu ◽  
Xin-chun Chen ◽  
...  
Keyword(s):  
T Cells ◽  
Viral Load ◽  
Cell Response ◽  
Th17 Cell ◽  
Influenza A ◽  
H1n1 Influenza ◽  
Cell Frequency ◽  
Viral Loads ◽  
Viral Shedding ◽  
Ifn Γ

Abstract Objective To explore whether age, disease severity, cytokines and lymphocytes in H1N1 influenza A patients correlate with viral load and clearance. Methods Total of 70 mild and 16 severe patients infected with H1N1 influenza A virus were enrolled in this study. Results It was found that the patients under 14 years old and severe patients displayed significantly higher viral loads and prolonged viral shedding periods compared with the patients over 14 years old and mild patients, respectively (P < 0.05). Moreover, the patients under 14 years old and severe patients displayed significantly lower Th17 cell frequency than the patients over 14 years old and mild patients (P < 0.01). The viral shedding period inversely correlated with the frequency of IL-17+IFN-γ-CD4+ T cells. Additionally, the decreased concentration of serum TGF-β correlated with the decreased frequency of IL-17+IFN-γ-CD4+ T cells. Conclusions Both younger and severe patients are associated with higher viral loads and longer viral shedding periods, which may partially be attributed to the impaired Th17 cell response.

scholarly journals Exacerbation of Influenza A Virus Disease Severity by Respiratory Syncytial Virus Co-Infection in a Mouse Model

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1630 ◽  
Author(s):  
Junu A. George ◽  
Shaikha H. AlShamsi ◽  
Maryam H. Alhammadi ◽  
Ahmed R. Alsuwaidi
Keyword(s):  
T Cells ◽  
Respiratory Syncytial Virus ◽  
Influenza A Virus ◽  
Influenza A ◽  
Immune Cell ◽  
Virus Disease ◽  
Viral Loads ◽  
Syncytial Virus

Influenza A virus (IAV) and respiratory syncytial virus (RSV) are leading causes of childhood infections. RSV and influenza are competitive in vitro. In this study, the in vivo effects of RSV and IAV co-infection were investigated. Mice were intranasally inoculated with RSV, with IAV, or with both viruses (RSV+IAV and IAV+RSV) administered sequentially, 24 h apart. On days 3 and 7 post-infection, lung tissues were processed for viral loads and immune cell populations. Lung functions were also evaluated. Mortality was observed only in the IAV+RSV group (50% of mice did not survive beyond 7 days). On day 3, the viral loads in single-infected and co-infected mice were not significantly different. However, on day 7, the IAV titer was much higher in the IAV+RSV group, and the RSV viral load was reduced. CD4 T cells were reduced in all groups on day 7 except in single-infected mice. CD8 T cells were higher in all experimental groups except the RSV-alone group. Increased airway resistance and reduced thoracic compliance were demonstrated in both co-infected groups. This model indicates that, among all the infection types we studied, infection with IAV followed by RSV is associated with the highest IAV viral loads and the most morbidity and mortality.

scholarly journals Respiratory Bacteria Stabilize and Promote Airborne Transmission of Influenza A Virus

mSystems ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Hannah M. Rowe ◽  
Brandi Livingston ◽  
Elisa Margolis ◽  
Amy Davis ◽  
Victoria A. Meliopoulos ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Bacterial Species ◽  
Bacterial Flora ◽  
Transmission Dynamics ◽  
Environmental Stability ◽  
Upper Respiratory Tract ◽  
Airborne Transmission ◽  
Content Type ◽  
Mortality And Morbidity

Infection with influenza A virus (IAV), especially when complicated with a secondary bacterial infection, is a leading cause of global mortality and morbidity. Gaining a greater understanding of the transmission dynamics of IAV is important during seasonal IAV epidemics and in the event of a pandemic. Direct bacterium-virus interactions are a recently appreciated aspect of infectious disease biology. Direct interactions between IAV and specific bacterial species of the human upper respiratory tract were found to promote the stability and infectivity of IAV during desiccation stress. Viral environmental stability is an important aspect during transmission, suggesting a potential role for bacterial respiratory communities in IAV transmission. Airborne transmission of IAV was abrogated upon depletion of nasal bacterial flora with topical antibiotics. This defect could be functionally complemented by S. pneumoniae coinfection. These data suggest that bacterial coinfection may be an underappreciated aspect of IAV transmission dynamics.

scholarly journals The PA Subunit of the Influenza Virus Polymerase Complex Affects Replication and Airborne Transmission of the H9N2 Subtype Avian Influenza Virus

Viruses ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 40 ◽  
Author(s):  
Mengchan Hao ◽  
Shaojie Han ◽  
Dan Meng ◽  
Rong Li ◽  
Jing Lin ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Avian Influenza ◽  
Avian Influenza Virus ◽  
Guinea Pigs ◽  
Influenza A ◽  
Reverse Genetics ◽  
Species Barrier ◽  
Airborne Transmission ◽  
H9n2 Subtype ◽  
Influenza A H1n1

The polymerase acidic (PA) protein is the third subunit of the influenza A virus polymerase. In recent years, studies have shown that PA plays an important role in overcoming the host species barrier and host adaptation of the avian influenza virus (AIV). The objective of this study was to elucidate the role of the PA subunit on the replication and airborne transmission of the H9N2 subtype AIV. By reverse genetics, a reassortant rSD01-PA was derived from the H9N2 subtype AIV A/Chicken/Shandong/01/2008 (SD01) by introducing the PA gene from the pandemic influenza A H1N1 virus A/swine/Shandong/07/2011 (SD07). Specific pathogen-free (SPF) chickens and guinea pigs were selected as the animal models for replication and aerosol transmission studies. Results show that rSD01-PA lost the ability of airborne transmission among SPF chickens because of the single substitution of the PA gene. However, rSD01-PA could infect guinea pigs through direct contact, while the parental strain SD01 could not, even though the infection of rSD01-PA could not be achieved through aerosol. In summary, our results indicate that the protein encoded by the PA gene plays a key role in replication and airborne transmission of the H9N2 subtype AIV.

scholarly journals Increased Viral Loads and Exacerbated Innate Host Responses in Aged Macaques Infected with the 2009 Pandemic H1N1 Influenza A Virus

2012 ◽  
Vol 86 (20) ◽  
pp. 11115-11127 ◽  
Author(s):  
L. Josset ◽  
F. Engelmann ◽  
K. Haberthur ◽  
S. Kelly ◽  
B. Park ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
H1n1 Influenza ◽  
Host Responses ◽  
Pandemic H1n1 ◽  
Viral Loads ◽  
Pandemic H1n1 Influenza

scholarly journals Recombinant Measles AIK-C Vaccine Strain Expressing Influenza HA Protein

Vaccines ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 149
Author(s):  
Takashi Ito ◽  
Takuji Kumagai ◽  
Yoshiaki Yamaji ◽  
Akihito Sawada ◽  
Tetsuo Nakayama
Keyword(s):  
Influenza A ◽  
Inflammatory Cells ◽  
Alveolar Wall ◽  
Viral Loads ◽  
Empty Vector ◽  
Influenza Hemagglutinin ◽  
Tnf Α ◽  
Cotton Rats ◽  
Ifn Γ ◽  
Ha Protein

Recombinant measles AIK-C vaccine expressing the hemagglutinin (HA) protein of influenza A/Sapporo/107/2013(H1N1pdm) (MVAIK/PdmHA) was constructed. Measles particle agglutination (PA) and influenza hemagglutinin inhibition (HI) antibodies were induced in cotton rats immunized with MVAIK/PdmHA. Cotton rats immunized with two doses of the HA split vaccine were used as positive controls, and higher HI antibodies were detected 3 weeks after the first dose. Following the challenge of A/California/07/2009(H1N1pdm), higher viral loads (107 TCID50/g) were detected in the lung homogenates of cotton rats immunized with the empty vector (MVAIK) or control groups than those immunized with MVAIK/Pdm HA (103 TCID50/g) or the group immunized with HA split vaccine (105 TCID50/g). Histopathologically, destruction of the alveolar structure, swelling of broncho-epithelial cells, and thickening of the alveolar wall with infiltration of inflammatory cells and HA antigens were detected in lung tissues obtained from non-immunized rats and those immunized with the empty vector after the challenge, but not in those immunized with the HA spilt or MVAIK/PdmHA vaccine. Lower levels of IFN-α, IL-1β, and TNF-α mRNA, and higher levels of IFN-γ mRNA were found in the lung homogenates of the MVAIK/PdmHA group. Higher levels of IFN-γ mRNA were detected in spleen cell culture from the MVAIK/PdmHA group stimulated with UV-inactivated A/California/07/2009(H1N1pdm). In conclusion, the recombinant MVAIK vaccine expressing influenza HA protein induced protective immune responses in cotton rats.

scholarly journals Cluster of Coronavirus Disease 2019 (COVID-19) in the French Alps, February 2020

2020 ◽  
Vol 71 (15) ◽  
pp. 825-832 ◽  
Author(s):  
Kostas Danis ◽  
Olivier Epaulard ◽  
Thomas Bénet ◽  
Alexandre Gaymard ◽  
Séphora Campoy ◽  
...  
Keyword(s):  
Viral Load ◽  
Influenza A ◽  
Index Case ◽  
Symptomatic Patient ◽  
Close Monitoring ◽  
Transmission Potential ◽  
French Alps ◽  
Health Authorities ◽  
Asymptomatic Individuals ◽  
Asymptomatic Case

Abstract Background On 7 February 2020, French Health authorities were informed of a confirmed case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in an Englishman infected in Singapore who had recently stayed in a chalet in the French Alps. We conducted an investigation to identify secondary cases and interrupt transmission. Methods We defined as a confirmed case a person linked to the chalet with a positive reverse-transcription polymerase chain reaction sample for SARS-CoV-2. Results The index case stayed 4 days in the chalet with 10 English tourists and a family of 5 French residents; SARS-CoV-2 was detected in 5 individuals in France, 6 in England (including the index case), and 1 in Spain (overall attack rate in the chalet: 75%). One pediatric case, with picornavirus and influenza A coinfection, visited 3 different schools while symptomatic. One case was asymptomatic, with similar viral load as that of a symptomatic case. Seven days after the first cases were diagnosed, 1 tertiary case was detected in a symptomatic patient with from the chalet a positive endotracheal aspirate; all previous and concurrent nasopharyngeal specimens were negative. Additionally, 172 contacts were monitored; all contacts tested for SARS-CoV-2 (N = 73) were negative. Conclusions The occurrence in this cluster of 1 asymptomatic case with similar viral load as a symptomatic patient suggests transmission potential of asymptomatic individuals. The fact that an infected child did not transmit the disease despite close interactions within schools suggests potential different transmission dynamics in children. Finally, the dissociation between upper and lower respiratory tract results underscores the need for close monitoring of the clinical evolution of suspected cases of coronavirus disease 2019.

scholarly journals Molecular basis of mammalian transmissibility of avian H1N1 influenza viruses and their pandemic potential

2017 ◽  
Vol 114 (42) ◽  
pp. 11217-11222 ◽  
Author(s):  
Mark Zanin ◽  
Sook-San Wong ◽  
Subrata Barman ◽  
Challika Kaewborisuth ◽  
Peter Vogel ◽  
...  
Keyword(s):  
Genetic Markers ◽  
Nuclear Export ◽  
Influenza A ◽  
Nonstructural Protein ◽  
H1n1 Influenza ◽  
Influenza Viruses ◽  
Upper Respiratory Tract ◽  
Influenza A Viruses ◽  
Airborne Transmission ◽  
Nonstructural Protein 1

North American wild birds are an important reservoir of influenza A viruses, yet the potential of viruses in this reservoir to transmit and cause disease in mammals is not well understood. Our surveillance of avian influenza viruses (AIVs) at Delaware Bay, USA, revealed a group of similar H1N1 AIVs isolated in 2009, some of which were airborne-transmissible in the ferret model without prior adaptation. Comparison of the genomes of these viruses revealed genetic markers of airborne transmissibility in the Polymerase Basic 2 (PB2), PB1, PB1-F2, Polymerase Acidic-X (PA-X), Nonstructural Protein 1 (NS1), and Nuclear Export Protein (NEP) genes. We studied the role of NS1 in airborne transmission and found that NS1 mutants that were not airborne-transmissible caused limited tissue pathology in the upper respiratory tract (URT). Viral maturation was also delayed, evident as strong intranuclear staining and little virus at the mucosa. Our study of this naturally occurring constellation of genetic markers has provided insights into the poorly understood phenomenon of AIV airborne transmissibility by revealing a role for NS1 and characteristics of viral replication in the URT that were associated with airborne transmission. The transmissibility of these viruses further highlights the pandemic potential of AIVs in the wild bird reservoir and the need to maintain surveillance.

scholarly journals Aerosol Susceptibility of Influenza Virus to UV-C Light

2012 ◽  
Vol 78 (6) ◽  
pp. 1666-1669 ◽  
Author(s):  
James J. McDevitt ◽  
Stephen N. Rudnick ◽  
Lewis J. Radonovich
Keyword(s):  
Influenza Virus ◽  
Relative Humidity ◽  
Influenza A ◽  
Virulent Strain ◽  
Airborne Transmission ◽  
Mortality And Morbidity ◽  
Virus Susceptibility ◽  
Air Disinfection ◽  
Uv C ◽  
Upper Room

ABSTRACTThe person-to-person transmission of influenza virus, especially in the event of a pandemic caused by a highly virulent strain of influenza, such as H5N1 avian influenza, is of great concern due to widespread mortality and morbidity. The consequences of seasonal influenza are also substantial. Because airborne transmission appears to play a role in the spread of influenza, public health interventions should focus on preventing or interrupting this process. Air disinfection via upper-room 254-nm germicidal UV (UV-C) light in public buildings may be able to reduce influenza transmission via the airborne route. We characterized the susceptibility of influenza A virus (H1N1, PR-8) aerosols to UV-C light using a benchtop chamber equipped with a UVC exposure window. We evaluated virus susceptibility to UV-C doses ranging from 4 to 12 J/m2at three relative humidity levels (25, 50, and 75%). Our data show that the Z values (susceptibility factors) were higher (more susceptible) to UV-C than what has been reported previously. Furthermore, dose-response plots showed that influenza virus susceptibility increases with decreasing relative humidity. This work provides an essential scientific basis for designing and utilizing effective upper-room UV-C light installations for the prevention of the airborne transmission of influenza by characterizing its susceptibility to UV-C.

scholarly journals Viral Factors Associated With the High Mortality Related to Human Infections With Clade 2.1 Influenza A/H5N1 Virus in Indonesia

2019 ◽  
Vol 70 (6) ◽  
pp. 1139-1146 ◽  
Author(s):  
Hana A Pawestri ◽  
Dirk Eggink ◽  
Siti Isfandari ◽  
Tran Tan Thanh ◽  
H Rogier van Doorn ◽  
...  
Keyword(s):  
High Mortality ◽  
Influenza A ◽  
H5n1 Virus ◽  
Fatal Outcome ◽  
Viral Rna ◽  
Viral Loads ◽  
Antiviral Responses ◽  
Amantadine Resistance ◽  
Human Infections ◽  
Over Time

Abstract Background Since their emergence in Indonesia in 2005, 200 human infections with clade 2.1 highly pathogenic avian influenza A/H5N1 virus have been reported, associated with exceptionally high mortality (84%) compared to regions affected by other genetic clades of this virus. To provide potential clues towards understanding this high mortality, detailed clinical virological analyses were performed in specimens from 180 H5N1 patients, representing 90% of all Indonesian patients and 20% of reported H5N1-infected patients globally. Methods H5N1 RNA was quantified in available upper- and lower-respiratory tract specimens as well as fecal and blood samples from 180 patients with confirmed infection between 2005 and 2017. Mutations in the neuraminidase and M2 genes that confer resistance to oseltamivir and adamantanes were assessed. Fatal and nonfatal cases were compared. Results High viral RNA loads in nasal and pharyngeal specimens were associated with fatal outcome. Mortality increased over time during the study period, which correlated with increasing viral RNA loads on admission. Furthermore, the prevalence of amantadine resistance–conferring M2 mutations increased over time, and viral loads were higher in patients infected with viruses that harbored these mutations. Compared to observations from other regions, viral RNA was detected more frequently in feces (80%) and particularly in blood (85%), and antiviral responses to oseltamivir appeared less pronounced. Conclusions These observations confirm the association of viral load with outcome of human H5N1 infections and suggest potential differences in virulence and antiviral responses to oseltamivir that may explain the exceptionally high mortality related to clade 2.1 H5N1 infections in Indonesia.

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