HMPV: China’s new virus outbreak explained

BEIJING: News reports and social media posts are warning of a new outbreak of a little-known virus called human metapneumovirus (HMPV) in China, but officials are yet to confirm this.

Instead, official reports from the Chinese Center for Disease Control and Prevention indicate that rates of multiple flu-like illnesses are on the rise in China, according to data up to the last week of 2024.

That data suggests that influenza is leading the outbreak, with 30.2 percent of tests coming back positive for it—an increase of 6.2 from the previous week—and 17.7 percent of people hospitalized with a severe respiratory illness testing positive for it. However, that same dataset indicates that rates of HMPV are ahead of other flu-like diseases—such as COVID-19, rhinovirus and adenovirus—linked to 6.2 percent of positive respiratory illness tests and 5.4 percent of respiratory-illness hospitalizations in China.

Human metapneumovirus (HMPV) is a virus that can cause flu-like illness in people of all ages, although some people are more at risk, including young children, older adults and people with weakened immune systems. The virus was only discovered as recently as 2001, but it is in the same family as respiratory syncytial virus (RSV), another flu-like virus. The more widespread use of testing for specific viruses among people with flu-like symptoms has resulted in an increased awareness of HMPV as a significant cause of respiratory illnesses.

Like other similar viruses, HMPV usually spreads from person to person through droplets from coughing and sneezing, through human contact such as hugging or kissing, and through touching surfaces and objects contaminated with the virus and then the mouth, nose or eyes.

In the U.S., HMPV circulates seasonally alongside the flu and similar diseases, and is most active in late winter and spring.

The U.S. Centers for Disease Control and Prevention (CDC) recommends several ways Americans can protect themselves from the virus: washing hands often with soap and water, avoid touching the face with unwashed hands and avoid close contact with sick people. People with flu-like symptoms are advised to cover their mouth when coughing or sneezing, wash their hands frequently with soap and water, avoid sharing cups and cutlery with others, avoid kissing others and stay at home to recover. HMPV symptoms are similar to other flu-like diseases, including coughing, a fever and a stuffy or runny nose. In some cases, sick people may experience a shortness of breath and this can progress to bronchitis—inflammation of the lungs’ airways—or pneumonia: inflammation of the lungs themselves. The length of the illness depends on the severity of the ill person’s symptoms, but is generally comparable to the flu. Because HMPV is a virus that was recognized relatively recently, there is no specific treatment available for it and no available vaccine. People with HMPV are advised to treat it like the flu and to stay at home while the body fights off infection. Currently, there is not enough information from reliable sources on the extent and severity of a possible HMPV outbreak in China to accurately predict the risk of a pandemic. However, this is a virus that already circulates among populations in China, the U.S. and elsewhere, so there is more herd immunity against it than there would be against a novel virus, such as COVID-19 at the beginning of the pandemic.