Cases of human metapneumovirus (HMPV) and other seasonal viruses are on the rise across the northern hemisphere in early 2025, according to the World Health Organization. While news reports and social media videos have caused concern about a potential HMPV outbreak in China,

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.

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.

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.

International media reports have said hospitals are being ‘overwhelmed’ by cases, but medical staff say that is not the case.

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

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

The United States witnesses a rise in HMPV cases, with positive test rates doubling between the start of December and the end of the month.