title: Absence of detectable influenza RNA transmitted via aerosol during various human respiratory activities--experiments from Singapore and Hong Kong.
abstract: Two independent studies by two separate research teams (from Hong Kong and Singapore) failed to detect any influenza RNA landing on, or inhaled by, a life-like, human manikin target, after exposure to naturally influenza-infected volunteers. For the Hong Kong experiments, 9 influenza-infected volunteers were recruited to breathe, talk/count and cough, from 0.1 m and 0.5 m distance, onto a mouth-breathing manikin. Aerosolised droplets exhaled from the volunteers and entering the manikin's mouth were collected with PTFE filters and an aerosol sampler, in separate experiments. Virus detection was performed using an in-house influenza RNA reverse-transcription polymerase chain reaction (RT-PCR) assay. No influenza RNA was detected from any of the PTFE filters or air samples. For the Singapore experiments, 6 influenza-infected volunteers were asked to breathe (nasal/mouth breathing), talk (counting in English/second language), cough (from 1 m/0.1 m away) and laugh, onto a thermal, breathing manikin. The manikin's face was swabbed at specific points (around both eyes, the nostrils and the mouth) before and after exposure to each of these respiratory activities, and was cleaned between each activity with medical grade alcohol swabs. Shadowgraph imaging was used to record the generation of these respiratory aerosols from the infected volunteers and their impact onto the target manikin. No influenza RNA was detected from any of these swabs with either team's in-house diagnostic influenza assays. All the influenza-infected volunteers had diagnostic swabs taken at recruitment that confirmed influenza (A/H1, A/H3 or B) infection with high viral loads, ranging from 10(5)-10(8) copies/mL (Hong Kong volunteers/assay) and 10(4)-10(7) copies/mL influenza viral RNA (Singapore volunteers/assay). These findings suggest that influenza RNA may not be readily transmitted from naturally-infected human source to susceptible recipients via these natural respiratory activities, within these exposure time-frames. Various reasons are discussed in an attempt to explain these findings.
authors.affiliation: Alberta Provincial Laboratory for Public Health, University of Alberta Hospital, Edmonton, Canada; Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada; Department of Laboratory Medicine, National University Hospital, Singapore, Singapore.
authors.forename: Julian W
authors.initials: JW
authors.lastname: Tang
authors.affiliation: Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China; Turning Point Alcohol and Drug Centre, Eastern Health, Melbourne, Australia; Eastern Health Clinical School, Monash University, Melbourne, Australia.
authors.forename: Caroline X
authors.initials: CX
authors.lastname: Gao
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore.
authors.forename: Gerald C
authors.initials: GC
authors.lastname: Koh
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Daniel
authors.initials: D
authors.lastname: Chu
authors.affiliation: Turning Point Alcohol and Drug Centre, Eastern Health, Melbourne, Australia; Eastern Health Clinical School, Monash University, Melbourne, Australia.
authors.forename: Cherie
authors.initials: C
authors.lastname: Heilbronn
authors.affiliation: Turning Point Alcohol and Drug Centre, Eastern Health, Melbourne, Australia; Eastern Health Clinical School, Monash University, Melbourne, Australia.
authors.forename: Belinda
authors.initials: B
authors.lastname: Lloyd
authors.affiliation: Department of Mechanical Engineering, University of Maryland, Baltimore, Maryland, United States of America.
authors.forename: Jovan
authors.initials: J
authors.lastname: Pantelic
authors.affiliation: Department of Laboratory Medicine, National University Hospital, Singapore, Singapore.
authors.forename: Andre D
authors.initials: AD
authors.lastname: Nicolle
authors.affiliation: Department of Laboratory Medicine, National University Hospital, Singapore, Singapore.
authors.forename: Christian A
authors.initials: CA
authors.lastname: Klettner
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: J S Malik
authors.initials: JS
authors.lastname: Peiris
authors.affiliation: Department of Building, School of Design and Environment, National University of Singapore, Singapore, Singapore.
authors.forename: Chandra
authors.initials: C
authors.lastname: Sekhar
authors.affiliation: Department of Building, School of Design and Environment, National University of Singapore, Singapore, Singapore.
authors.forename: David K W
authors.initials: DK
authors.lastname: Cheong
authors.affiliation: Department of Building, School of Design and Environment, National University of Singapore, Singapore, Singapore.
authors.forename: Kwok Wai
authors.initials: KW
authors.lastname: Tham
authors.affiliation: Department of Laboratory Medicine, National University Hospital, Singapore, Singapore; Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
authors.forename: Evelyn S C
authors.initials: ES
authors.lastname: Koay
authors.affiliation: Department of Family Medicine and Primary Healthcare, Hong Kong West Cluster, Hospital Authority, Hong Kong SAR, China.
authors.forename: Wendy
authors.initials: W
authors.lastname: Tsui
authors.affiliation: Department of Family Medicine and Primary Healthcare, Hong Kong West Cluster, Hospital Authority, Hong Kong SAR, China.
authors.forename: Alfred
authors.initials: A
authors.lastname: Kwong
authors.affiliation: University Health Service, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Kitty
authors.initials: K
authors.lastname: Chan
authors.affiliation: Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Yuguo
authors.initials: Y
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000328:Adult; D003371:Cough; D045853:Exhalation; D005260:Female; D006723:Hong Kong; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics*; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics*; D009981:Influenza B virus / Q000235:genetics*; D007251:Influenza, Human / Q000635:transmission / Q000821:virology*; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D012367:RNA, Viral / Q000235:genetics* / Q000302:isolation & purification; D012119:Respiration; D012846:Singapore; D019562:Viral Load
chemical_list: D012367:RNA, Viral