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.

Most HMPV infections are mild, resembling bouts of the common cold. But severe cases can result in bronchitis or pneumonia, particularly among infants, older adults and immunocompromised people. Patients with pre-existing lung conditions, such as asthma, chronic obstructive pulmonary disease or emphysema, are at higher risk of severe outcomes.

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.

Rising cases of common respiratory illnesses in China and elsewhere around the Northern Hemisphere are within the range expected for winter, WHO says.

A rise in cases of human metapneumovirus in China is stoking fears of a new health crisis, though authorities and experts say prospects for a sequel to the COVID-19 pandemic are remote. The big picture: HMPV is similar to respiratory syncytial virus,

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