And now, the human metapneumovirus, or HMPV for short, is infecting thousands of Americans around the country. The highly contagious virus, which belongs to the same group as respiratory syncytial virus (RSV),

Disease experts have called on Chinese authorities to reveal critical data about a worrying outbreak of HMPV, which can be deadly for those with underlying health conditions

As cases of the HMPV virus continue to increase in the U.S. and in China, here's what you need to know about the virus.