In this week's RAZOR special we cover a range of COVID-19 related stories.

Herd immunity is the term used to describe the proportion of a population that needs to be vaccinated in order to control an infectious disease. Measles is an example, where most of the population is vaccinated, which, in turn, protects those who are not.

However, the World Health Organisation has labelled herd immunity a dangerous concept when talking about COVID-19. Emma Keeling speaks with virologist Dr Jeremy Rossman and asks him if he agrees.

As lockdown restrictions ease around the world, but we remain cautious of subsequent outbreaks, people will start walking, running and cycling more often. Shini Somara Speaks to Bert Blocken about his study which has mapped the flow of particles we breathe out to see how they are affected by rapid movement. 

The whole world has its hopes set on a vaccine to coronavirus. In the UK an effort led by an Oxford University team has begun human trials, with the co-operation of research hospitals around the country, such as St George's in London. 1,000 volunteers have been injected, half with the proposed vaccine and the other half with another already established vaccine. This is what's known as a double-blind trial.

But if we are trying to get rid of the virus by other means such as social distancing and lockdowns – how will we know if a vaccine has been successful? Producer Neil Cairns put that question to Professor Paul Heath of St George's Hospital, London.

COVID-19 is a respiratory pandemic. It causes death primarily through pneumonia. But according to emergency medical practitioner Dr Richard Levitan, of New Hampshire, COVID can be confusing because patients presenting to hospital can have severe COVID pneumonia and yet not feel short of breath.

Cross-species transmission, or spillover, is the most significant cause of disease emergence in humans, and other species. Professor Richard Kock is an infectious diseases specialist at the Royal Veterinary College, University of London. He believes that the solution to cross species infection is to reform our agricultural practices and our whole relationship with the natural world. He began by telling RAZOR producer, Neil Cairns about the Nipah virus outbreak in Malaysia in 1999.