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.

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,

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.