HMPV: What to know about China's human metapneumovirus cases

Recently, a surge in human metapneumovirus (HMPV) cases, a flu-like illness, in China has sparked concerns about a potential repeat of the COVID-19 pandemic. Social media has been flooded with images of hospitals crowded with masked patients, but health experts point out that HMPV is different from the coronavirus and has been around for years.

Experts state that what China and other countries are currently experiencing is simply the seasonal increase of HMPV commonly seen in winter. First discovered in the Netherlands in 2001, HMPV spreads through direct person-to-person contact or contact with contaminated surfaces. For most people, the virus causes mild upper respiratory infections with symptoms often indistinguishable from the flu, including cough, fever, and nasal congestion.

Young children, especially those under the age of two, are most susceptible to the virus. Dr. Hsu Li Yang, an infectious disease expert in Singapore, noted that people with weakened immune systems, including the elderly and those with advanced cancer, are also at greater risk. If infected, a small number of immunocompromised individuals may develop more severe illness, with lung involvement, presenting with wheezing, shortness of breath, and asthma symptoms. “Many will require hospitalisation, and a small percentage are at risk of dying from the infection,” said Dr. Hsu.

Why are HMPV cases rising in China? Like many respiratory infections, HMPV is most active in late winter and spring. This is because the virus survives better in colder environments and spreads more easily between people when they are indoors with closed windows. In northern China, the current HMPV peak coincides with the cold weather expected to last through March. Jacqueline Stephens, an epidemiologist at Flinders University in Australia, stated that many northern hemisphere countries, including the United States, are also experiencing an increase in HMPV infections. “While concerning, this increase in prevalence is likely a seasonal increase common during the winter,” she said.

The World Health Organization (WHO) is monitoring flu-like illness rates in the northern hemisphere and says it has not received reports of any unusual outbreak patterns in China or elsewhere. The WHO stated that Chinese authorities have confirmed that the healthcare system is not overwhelmed and that no emergency declarations or responses have been issued to date. In the UK, HMPV rates have been steadily increasing since October 2024. The UK Health Security Agency (UKHSA) has not published the number of recorded cases, but its latest data shows that the proportion of people testing positive rose sharply in the third week of December, remaining at high levels in the following week. However, the UKHSA says this is fully in line with normal seasonal trends, with disease levels in GP surgeries and hospitals also within expectations.

Experts say that concerns about a repeat of the COVID-19 pandemic are overblown, noting that such events are usually caused by new viruses, which HMPV is not. The disease has been present globally and has been around for decades. This means that people around the world have "a degree of existing immunity" due to previous exposure, Dr. Hsu said. Professor Paul Hunter, a professor of medicine at the University of East Anglia in the UK, stated, “Almost every child will have had HMPV at least once before they’re five, and we can expect to get repeat infections multiple times in our lives. I don’t think there’s any indication at the moment that there is a more serious global problem emerging.”

However, health officials advise taking sensible precautions to avoid contracting HMPV and other respiratory illnesses, including wearing masks in crowded places, avoiding crowds where possible (if you are at higher risk of serious illness), washing hands regularly, and safely disposing of tissues. People may also want to consider getting vaccinated against other respiratory illnesses such as the flu. In the UK, pregnant women and adults aged 75 to 79 are advised to get the respiratory syncytial virus (RSV) vaccine. RSV is a common infection that causes coughs and colds, but can sometimes be serious for babies and older people.