Since their inception in March 1972, Keystone Symposia on Molecular and Cellular Biology have brought together scientists from across the globe to discuss key biological topics. Now in its 40th year, it is a completely independent, nonprofit organization devoted solely to providing outstanding scientific conferences in all areas of the biological and biomedical sciences. Towards the end of May 2011, over 200 virologists and immunologists came to Hong Kong, an appropriate setting given the emergence of H5N1, to discuss influenza virus and host interactions. The meeting, expertly organized by Siamon Gordon (University of Oxford, Oxofrd, UK), Malik Peiris (University of Hong Kong, Hong Kong, China) and Kanta Subbarao (NIAID, NIH, MD, USA), took place in the aftermath of the first pandemic in 40 years and provided great insight into both pandemic H1N1 and H5N1. This article focuses on some of the recurring themes that were discussed during the week.