Rockey, N. C.; Le Sage, V.; Shephard, M.; Vargas-Maldonado, N.; French, A. J.; Walter, S.; Ferreri, L. M.; Holmes, K. E.; VanInsberghe, D.; Clack, H.; Prussin, A. J.; Lowen, A. C.; Marr, L.; Lakdawala, S.

Sustained community spread of influenza viruses relies on efficient person to person transmission. Current experimental transmission systems do not mimic environmental conditions (e.g., air exchange rates, flow patterns), host behaviors or exposure durations relevant to real-world settings. Therefore, results from these traditional systems may not be representative of influenza virus transmission in humans. To address this pitfall, we developed a modified, more realistic transmission setup and used it to investigate the impact of ventilation rates on transmission in a close-range, play-based scenario. In this setup, four immunologically naive recipient ferrets were exposed to a donor ferret infected with a genetically barcoded 2009 H1N1 virus (H1N1pdm09) for four hours. The ferrets interacted in a shared space that included toys, similar to a child care setting. The transmission efficiency was determined under conditions of low and high ventilation rates; air exchange rates of ~ 1.3 hr-1 and 23 hr-1, respectively. Despite the large difference in ventilation rate, transmission efficiency was the same, 50 percent in two independent replicate studies. The presence of infectious virus or viral RNA on surfaces and in air throughout the exposure area was similar regardless of ventilation rate. While high viral genetic diversity in donor ferret nasal washes was maintained during infection, recipient ferret nasal washes displayed low diversity, revealing a narrow transmission bottleneck regardless of ventilation rate. Our findings indicate that in exposures characterized by frequent close-range, play-based interactions and the presence of fomites, ventilation does not significantly impact transmission efficiency.