What is the current thinking - in Ireland and abroad - about wearing masks?

People living in Ireland do not have to wear masks as part of the effort to curb the spread of Covid-19 - but people in New York and the Czech Republic do. So should we be wearing masks, or not? What does the science say? And are homemade cloth masks any use? On this week's episode of The Explainer, we take a look at the question of mask-wearing.