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

In China, reports of HMPV infections have indeed been rising in recent weeks in the more northerly regions. But so have reports of all the other respiratory pathogens including seasonal flu, rhinovirus and RSV.

Cases are climbing in China, but the situation is very different from when COVID-19 emerged five years ago, medical experts say. HMPV is common and decades old.