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.

China’s winter illness season is less severe compared to the year before, according to data from its health authority. But the proliferation of a long-standing though little-known pathogen called human metapneumovirus (hMPV) has been raising alarm both at home and in other countries.

WHO said, ‘Human metapneumovirus, hMPV is not a new virus’, adding that it generally spreads in winter and spring.

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.

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