By Daniel Lawler An anti-Covid drug widely used across the world may have caused mutations in the virus, researchers said on Monday, but there was no evidence that the changes had led to more dangerous variants. Pharmaceutical giant Merck’s antiviral pill molnupiravir was one of the earliest treatments rolled out during the pandemic to prevent Covid becoming more severe in vulnerable people. The drug, which is taken orally over a five-day course, works mainly by […]