title: Viral Shedding and Transmission Potential of Asymptomatic and Paucisymptomatic Influenza Virus Infections in the Community.
abstract: Influenza virus infections are associated with a wide spectrum of disease. However, few studies have investigated in detail the epidemiological and virological characteristics of asymptomatic and mild illness with influenza virus infections.
  
  
  
  In a community-based study in Hong Kong from 2008 to 2014, we followed up initially healthy individuals who were household contacts of symptomatic persons with laboratory-confirmed influenza, to identify secondary infections. Information from daily symptom diaries was used to classify infections as symptomatic (≥2 signs/symptoms, including fever ≥37.8°C, headache, myalgia, cough, sore throat, runny nose and sputum), paucisymptomatic (1 symptom only), or asymptomatic (none of these symptoms). We compared the patterns of influenza viral shedding between these groups.
  
  
  
  We identified 235 virologically confirmed secondary cases of influenza virus infection in the household setting, including 31 (13%) paucisymptomatic and 25 (11%) asymptomatic cases. The duration of viral RNA shedding was shorter and declined more rapidly in paucisymptomatic and asymptomatic than in symptomatic cases. The mean levels of influenza viral RNA shedding in asymptomatic and paucisymptomatic cases were approximately 1-2 log10 copies lower than in symptomatic cases.
  
  
  
  The presence of influenza viral shedding in patients with influenza who have very few or no symptoms reflects their potential for transmitting the virus to close contacts. These findings suggest that further research is needed to investigate the contribution of persons with asymptomatic or clinically mild influenza virus infections to influenza virus transmission in household, institutional, and community settings.
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Dennis K M
authors.initials: DK
authors.lastname: Ip
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Ontario, Canada.
authors.forename: Lincoln L H
authors.initials: LL
authors.lastname: Lau
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Nancy H L
authors.initials: NH
authors.lastname: Leung
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Vicky J
authors.initials: VJ
authors.lastname: Fang
authors.affiliation: Department of Microbiology, , University of Hong Kong, Hong Kong.
authors.forename: Kwok-Hung
authors.initials: KH
authors.lastname: Chan
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.|Centre of Influenza Research, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: Daniel K W
authors.initials: DK
authors.lastname: Chu
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Leung
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.|Centre of Influenza Research, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: J S Malik
authors.initials: JS
authors.lastname: Peiris
authors.affiliation: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Uyeki
authors.affiliation: WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
mesh_terms: D000293:Adolescent; D000328:Adult; D058070:Asymptomatic Diseases; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009980:Influenza A virus / Q000145:classification / Q000235:genetics; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D019562:Viral Load; D017201:Virus Shedding; D055815:Young Adult
keywords: asymptomatic; epidemiology.; influenza virus; public health; viral shedding