As China experiences a rise in respiratory infections this winter, one little-known virus has gotten a lot of attention – and some people may worry whether the rise in cases could be felt more broadly around the world.

Rising cases of common respiratory illnesses in China and elsewhere around the Northern Hemisphere are within the range expected for winter, with no unusual outbreaks reported, the World Health Organization said.

As China continues to monitor an increase in cases of human metapneumovirus (HMPV), here's what you need to know about the illness.