Respiratory Syncytial Virus is an extremely common infection in humans. Generally in healthy adults there is little or no disease but in infants or the elderly this lung infection can often be fatal and we do not yet have a vaccine. Over at Rule of 6ix, I ask a couple of questions to the first author of a recent PNAS paper looking at how this virus infects and causes disease in an in vitro model of a child's lung. Here Remi Villenave, a post-doc at my institute explains his work, why he did it and what it tells us about this deadly disease.