Professor Paul Hunter from the University of East Anglia notes that almost every child contracts HMPV by five years of age, with reinfections occurring throughout life. “HMPV typically causes cold-like symptoms that recover by themselves within 2 to 5 days. Severe cases are rare but can occur in vulnerable groups,” he says.

While cases are climbing in China, the situation is very different from what it was when Covid-19 emerged five years ago, medical experts say. HMPV is common and decades old.

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