Concentrations and size distributions of airborne influenza A viruses measured indoors at a health centre, a day-care centre and on aeroplanes

The relative importance of the aerosol transmission route for influenza remains contentious. To determine the potential for influenza to spread via the aerosol route, we measured the size distribution of airborne influenza A viruses. We collected size-segregated aerosol samples during the 2009–2010 flu season in a health centre, a day-care facility and onboard aeroplanes. Filter extracts were analysed using quantitative reverse transcriptase polymerase chain reaction. Half of the 16 samples were positive, and their total virus concentrations ranged from 5800 to 37 000 genome copies m −3 . On average, 64 per cent of the viral genome copies were associated with fine particles smaller than 2.5 µm, which can remain suspended for hours. Modelling of virus concentrations indoors suggested a source strength of 1.6 ± 1.2 × 10 5 genome copies m −3 air h −1 and a deposition flux onto surfaces of 13 ± 7 genome copies m −2 h −1 by Brownian motion. Over 1 hour, the inhalation dose was estimated to be 30 ± 18 median tissue culture infectious dose (TCID 50 ), adequate to induce infection. These results provide quantitative support for the idea that the aerosol route could be an important mode of influenza transmission.

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Development and application of a real-time RT-PCR assay to rapidly detect H2 subtype avian influenza A viruses

Journal of Veterinary Diagnostic Investigation ◽

10.1177/1040638721994810 ◽

2021 ◽

pp. 104063872199481

Author(s):

Yixin Xiao ◽

Fan Yang ◽

Fumin Liu ◽

Hangping Yao ◽

Nanping Wu ◽

...

Keyword(s):

Avian Influenza ◽

Real Time ◽

Influenza A ◽

Minor Groove Binder ◽

Rt Pcr ◽

Influenza A Viruses ◽

Pcr Assay ◽

Infectious Dose ◽

The Matrix ◽

Taqman Minor Groove Binder

The H2 subtypes of avian influenza A viruses (avian IAVs) have been circulating in poultry, and they have the potential to infect humans. Therefore, establishing a method to quickly detect this subtype is pivotal. We developed a TaqMan minor groove binder real-time RT-PCR assay that involved probes and primers based on conserved sequences of the matrix and hemagglutinin genes. The detection limit of this assay was as low as one 50% egg infectious dose (EID50)/mL per reaction. This assay is specific, sensitive, and rapid for detecting avian IAV H2 subtypes.

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Development and Validation of a Concentration Method for the Detection of Influenza A Viruses from Large Volumes of Surface Water

Applied and Environmental Microbiology ◽

10.1128/aem.02484-10 ◽

2011 ◽

Vol 77 (11) ◽

pp. 3802-3808 ◽

Cited By ~ 37

Author(s):

Nathalie Deboosere ◽

Srey Viseth Horm ◽

Anthony Pinon ◽

Jessica Gachet ◽

Chloé Coldefy ◽

...

Keyword(s):

Surface Water ◽

Lake Water ◽

Water Samples ◽

Influenza A ◽

Detection Threshold ◽

Glass Wool ◽

Influenza A Viruses ◽

M Gene ◽

Infectious Dose ◽

Surface Water Samples

ABSTRACTContamination of lakes and ponds plays an essential role as a reservoir of avian influenza A virus (AIV) in the environment. A method to concentrate waterborne AIV is a prerequisite for the detection of virus present at low levels in water. The aim of this study was to develop and validate a method for the concentration and detection of infectious AIV from large volumes of surface water samples. Two filtration systems, glass wool and electropositive NanoCeram filter, were studied. The individual effects of filtration-elution and polyethylene glycol (PEG) concentration parameters on the recovery efficiency of the H1N1 strain from 10-liter surface water samples were assessed. An ultimate 1% recovery rate of infectious viruses was achieved with the optimal protocol, corresponding to filtration through glass wool, followed by a viral elution step and then a PEG concentration. This method was validated for the detection of highly pathogenic H5N1 strains from artificially contaminated larger water volumes, from 10 to up to 50 liters, from different sources. The viral recovery efficiencies ranged from 0.01% to 7.89% and from 3.63% to 13.79% with lake water and rainwater, respectively. A theoretical detection threshold of 2.25 × 102TCID50(50% tissue culture infectious dose) in the filtered volume was obtained for seeded lake waters by M gene reverse transcriptase PCR (RT-PCR). Moreover, the method was used successfully in field studies for the detection of naturally occurring influenza A viruses in lake water in France.

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A Downward Trend of the Ratio of Influenza RNA Copy Number to Infectious Viral Titer in Hospitalized Influenza A-Infected Patients

Open Forum Infectious Diseases ◽

10.1093/ofid/ofv166 ◽

2015 ◽

Vol 2 (4) ◽

Cited By ~ 5

Author(s):

Liesbeth Van Wesenbeeck ◽

David D'Haese ◽

Jeroen Tolboom ◽

Hanne Meeuws ◽

Dominic E. Dwyer ◽

...

Keyword(s):

Copy Number ◽

Influenza A ◽

Clinical Symptoms ◽

Viral Titer ◽

Infectious Dose ◽

Nasal Swabs ◽

Rate Of Decay ◽

Log Ratio ◽

The Relationship ◽

Tissue Culture Infectious Dose

Abstract Background. Efficacy endpoints in influenza clinical trials may include clinical symptoms and virological measurements, although virology cannot serve as the primary endpoint. We investigated the relationship between influenza A RNA copy number and quantity of infectious viruses in hospitalized influenza patients. Methods. One hundred fifty influenza-infected, hospitalized patients were included in this prospective cohort study spanning the 2012–2013 influenza season. Daily nasopharyngeal samples were collected during hospitalization, and influenza A RNA copy number and infectious viral titer were monitored. Results. The decay rate for 50% tissue culture infectious dose (TCID50) was 0.51 ± 0.14 log10 TCID50/mL per day, whereas the RNA copy number decreased at a rate of 0.41 ± 0.04 log10 copies/mL per day (n = 433). The log ratio of the RNA copy number to the infectious viral titer within patient changes significantly with −0.25 ± 0.09 units per day (P = .0069). For a 12-day observation period, the decay corresponds to a decline of this ratio of 3 log influenza RNA copies. Conclusions. Influenza RNA copy number in nasal swabs is co-linear with culture, although the rate of decay of cell culture-based viral titers was faster than that observed with molecular methods. The study documented a clear decreasing log ratio of the RNA copy number to the infectious viral titer of the patients over time.

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The Role of Influenza A Virus Hemagglutinin Residues 226 and 228 in Receptor Specificity and Host Range Restriction

Journal of Virology ◽

10.1128/jvi.72.9.7626-7631.1998 ◽

1998 ◽

Vol 72 (9) ◽

pp. 7626-7631 ◽

Cited By ~ 168

Author(s):

Angela Vines ◽

Krisna Wells ◽

Mikhail Matrosovich ◽

Maria R. Castrucci ◽

Toshihiro Ito ◽

...

Keyword(s):

Amino Acids ◽

Host Range ◽

Influenza A ◽

Influenza Viruses ◽

Influenza A Viruses ◽

Range Restriction ◽

Human Virus ◽

Infectious Dose ◽

H3 Subtype ◽

Host Range Restriction

ABSTRACT Influenza A viruses can be isolated from a variety of animals, but their range of hosts is restricted. For example, human influenza viruses do not replicate in duck intestine, the major replication site of avian viruses in ducks. Although amino acids at positions 226 and 228 of hemagglutinin (HA) of the H3 subtype are known to be important for this host range restriction, the contributions of specific amino acids at these positions to restriction were not known. Here, we address this issue by generating HAs with site-specific mutations of a human virus that contain different amino acid residues at these positions. We also let ducks select replication-competent viruses from a replication-incompetent virus containing a human virus HA by inoculating animals with 1010.5 50% egg infectious dose of the latter virus and identified a mutation in the HA. Our results showed that the Ser-to-Gly mutation at position 228, in addition to the Leu-to-Gln mutation at position 226 of the HA of the H3 subtype, is critical for human virus HA to support virus replication in duck intestine.

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