As the UK gradually begins to ease out of lockdown, Marnie explores how engineers are hoping to reduce the spread of Covid-19. We’ve learned how infected people exhale droplets and aerosols, containing the virus, and how we can then either inhale them, or transfer them to our faces by touching contaminated surfaces. Many shops already have screens and physical barriers, while schools and offices are re-configuring desks and walkways. What role does the environment play in our overall risk of becoming infected and what can we do about it? This is the focus of the SAGE Environmental Working Group. Marnie talks to its Chair, Catherine Noakes, Professor of Environmental Engineering for Buildings at Leeds University. Minimising the risks that contaminated surfaces pose is a key challenge that engineers are now trying to address. Marnie asks Birmingham University Research Scientist, Felicity de Cogan, about the surface she created which kills bacteria in seconds. She's now re-purposing the technology to kill the virus that causes Covid-19. If her laboratory studies prove that it kills the virus as quickly, as she hopes, the technology could be used to create antiviral PPE that can be re-used rather than thrown away. Epidemiology has been thrust into the spotlight in recent months, helping us track the viral threat facing all of us. But companion animal epidemiology - which studies disease in pet populations - is a much younger field. It’s one that’s starting to search for the answers to another puppy-related conundrum that’s been puzzling BBC Inside Science reporter Geoff Marsh - should he get puppy Kevin castrated? Neutering has become a cultural norm in the UK. But the health risks to neutered male dogs include cancers and joint disorders in some breeds. The operation and anaesthetic carries some risk as does the age of the dog when the operation is carried out. The risk of dog populations exploding with hundreds of un-neutered dogs is low, because most owners control their dogs to such a degree the chance of unplanned mating doesn't come up. But neutering can help with some behavioural problems in pet dogs. So what is the answer? Will Kevin remain intact? Presenter - Marnie Chesterton Producers - Beth Eastwood and Fiona Roberts