Environmental Health, Environmental Justice
Influenza Virus in Respiratory Droplets Produced by Naturally and Experimentally Infected Patients
(School of Public Health (UMD) Maryland Institute for Applied Environmental Health Doctoral Student)
Background: Controlled clinical trials of influenza transmission from artificially inoculated individuals have the potential to test hypotheses about modes of transmission. Here we compared the influenza virus content of fine (<5μm) and coarse (≥5μm) aerosol particles in expired breath from persons with experimental infection (EI) and natural community acquired infection (CAI) to determine whether experimental human infection can serve as an appropriate model for simulating influenza transmission. Methods: We recruited CAI cases from the UMD campus and studied EI (by nasal inoculation with GMP A/Wisconsin/H3N2/67/2005) enrolled in a study of influenza transmission. Exhaled breath samples from both groups were collected using the G-II bioaerosol sampler following identical sampling protocols. CAI samples were subtyped using CDC’s panel and all were quantified alongside EI samples in the same lab by RTqPCR using CDC Taqman® primers and probes for influenza A virus. Findings: We collected breath samples from 86 CAI cases with confirmed H3N2 infection and 52 EI cases. We detected influenza virus in coarse aerosol from 12% coarse (GM=42, GSD=2.2, range 30 - 1.8*102) of the EI cases and 56% (GM=2.5*102, GSD=15, range from 7.8 -2.3*106) of the CAI cases. We detected influenza virus in fine aerosol from 20 % (GM=76, GSD=2.9, range 23-5.2*102) of the EI cases and 86% (GM=7.4*102, GSD=13, range 18-3.0*105) of the CAI cases. The frequency and intensity of shedding was much lower from EI cases than CAI cases. Experimentally infected donors may have had immunity not detected by serology or the partially attenuated laboratory virus may not have been capable of inducing significant shedding. However, based on historical data, the most likely explanation is that nasal inoculation produced mild infection with minimal shedding. Nasal inoculation EI does not appear to produce an adequate model for clinical trials to study infection transmission.
Importance to public health: