The authorities in Saudi Arabia say the number of cases of the Middle East Respiratory Syndrome, or Mers, in the country has more than doubled since the start of April. The health ministry also said over the weekend that it has seen the biggest daily increase of the mysterious syndrome also known as Mers. Earlier, the US confirmed its first case in a man who had recently returned from Saudi Arabia. There are no vaccines or antiviral treatments for Mers and researchers are scrambling to understand the virus. New research shows camels have been infected with Mers but officials do not know how it is spreading to humans. Ian Lipkin, an expert from Columbia University in New York, comments about what is known so far.