Measurements of influenza virus RNA in cough-generated aerosols
WILLIAM G. LINDSLEY (1), Francoise M. Blachere (1), Robert E. Thewlis (1), Abhishek Vishnu (2), Kristina A. Davis (3), Gang Cao (1), Jan E. Palmer (4), Karen E. Clark (4), Melanie A. Fisher (3), Rashida Khakoo (3), Stephen M. Davis (5), Bean T. Chen (1) and Donald H. Beezhold (1)
(1) NIOSH, (2) Department of Community Medicine, West Virginia University, (3) Department of Medicine, West Virginia University, (4) Well WVU Student Health, West Virginia University, (5) Department of Emergency Medicine, West Virginia University
Abstract Number: 154
Preference: Platform Presentation
Last modified: April 26, 2010
Working Group: Biological Aerosol Detection and Sampling
Influenza continues to be a major public health concern because of the potential for a severe pandemic. However, the relative importance of the different possible modes for influenza transmission, particularly airborne transmission, remains unclear. To better understand the potential for airborne transmission in the spread of influenza, we measured the amount and size of aerosol particles containing influenza virus RNA that were produced by patients when they coughed. Subjects were recruited from patients presenting at a student health clinic with influenza-like symptoms. Nasal swabs were collected from volunteers and they were asked to cough three times into a modified piston-style medical spirometer. After each cough, the cough-generated aerosol was collected using a NIOSH two-stage bioaerosol cyclone sampler. The amount of influenza viral RNA contained in each stage of the sampler was then analyzed using quantitative real-time PCR targeted at the influenza matrix gene M1. Forty-eight subjects were tested, of whom 38 had influenza-positive nasal swabs. Influenza virus RNA was detected in coughs from 32 subjects (84%). Thirty-five percent of the influenza RNA was contained in particles > 4 micrometer in aerodynamic diameter, while 23% was in particles 1 to 4 micrometer and 42% in particles < 1 micrometer. The total copy number ranged from 1 to 407 viral particles in all three coughs combined (mean 75, SD 88). These results show that influenza patients emit measurable amounts of aerosol particles containing influenza virus while coughing and that much of the viral RNA is contained within particles in the respirable size range. The results support the idea that the airborne route may be an important pathway for influenza transmission, especially in the immediate vicinity of an influenza patient.