Changes to the bacteria that live inside all of us are responsible for increasing the number of people with allergies, suggests new research. The programme investigates this claim by conducting a unique experiment with two allergic families in order to find out just what it is in the modern world that is to blame.
Dr Chris van Tulleken, Dr Hannah Fry and Michael Mosley examine the latest research and explore some of the big questions about Covid-19 and the pandemic it has created. Michael visits the UK government's high-security laboratory Porton Down, where vaccines are being tested. He also uncovers what the experience of the 2002 SARs epidemic reveals about this one. Both were caused by coronaviruses, but certain key changes to today's virus have allowed it to infect the world, where SARs was contained.
This time, we meet a man who feels no pain, a woman who can smell Parkinson's disease, a man who can remember every face he has ever seen and a survivor of a head injury who woke up to find he could suddenly play the piano. These remarkable cases are shedding new light on one of the most mysterious parts of the human body - our brain.