Iran was one of the first countries to be hit hard by the coronavirus. In the first population wide survey of infection rates in a Middle Eastern country, Iranian medical researchers now estimate that about one in five people on average were infected during its first wave in 18 cities in the country. But the rate varies enormously from city to city. In the city of Rasht, they estimate more than 70% of the population caught the virus. Claudia Hammond talks to Iranian infectious disease researcher Maryam Darvishian about the findings and what they mean for Iran’s attempts to control the virus today. We look at the sleep hygiene plight of international students whose study and sleep cycles have been thrown into chaos because of Covid travel restrictions. We hear the experiences of a student in Singapore studying remotely at Columbia University in New York. Her classes are usually in the dead of night Singapore time. Harvard sleep researcher Jeanne Duffy advises on the best ways for students to plan their work/sleep patterns. When surgical patients are under general anaesthetic, playing them soothing music and comforting messages may reduce the pain that they experience and the need for opioid pain relief in the 24 hours after their operations. This is the conclusion of a randomised study of about 400 patients undergoing surgery in five German hospitals. Claudia talks to anaesthesiologist Ernil Hansen of Regensberg University who explains how this might be working to make post-operative recovery more comfortable and less reliant on strong analgesic drugs. Claudia’s studio guest this week is BBC Medicine and Science correspondent James Gallagher, talking about Covid-19 vaccines, how our genes influence the severity of Covid illness and how ear wax might improve blood sugar monitoring for diabetes. Presenter: Claudia Hammond Producer: Andrew Luck-Baker (Picture: People wearing protective masks walk through a street in Tehran in July 2020. Photo credit: Fatemeh Bahrami/Anadolu Agency/Getty Images.)