Rising HMPV cases in China are 'what we would expect to see' in winter, health officials say

This winter, China has seen an increase in respiratory infections, with a little-known virus drawing widespread attention. Concerns have arisen about whether this rise in cases could have broader global implications.

Human metapneumovirus (HMPV) can cause upper and lower respiratory illnesses in people of all ages. Data released last week by the Chinese Center for Disease Control and Prevention showed an increase in cases in China in recent weeks. However, HMPV typically circulates during the winter in the Northern Hemisphere, and the Chinese CDC data also showed increases in other common respiratory infections, including seasonal influenza and respiratory syncytial virus (RSV).

World Health Organization spokesperson Margaret Harris stated at a press briefing on Tuesday, "The levels of respiratory infections reported in China are within the normal range. This is what we would expect to see in the winter." She added that hospital utilization in China is lower than at the same time last year and that the country has not triggered an emergency declaration or emergency response due to these respiratory infections, easing concerns.

Harris said, “With regard to human metapneumovirus, it’s not a new virus. It was first discovered in 2001. It’s been around in human populations for a long time. It’s a common virus that circulates in the winter and spring.” In the United States, the CDC tracks HMPV cases in the same way it tracks other respiratory virus circulation. It’s estimated that HMPV causes about 10% to 12% of respiratory illnesses in children; most people contract HMPV before the age of 5 and can be reinfected throughout their lives.

Data shows that HMPV cases have been occurring more frequently since November and have been rising since then. However, compared to other common viruses, the percentage of weekly respiratory infection tests that came back positive for HMPV has remained low, at 1.94% as of December 28. By comparison, influenza was 18.71% and COVID-19 was 7.10% that week. Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists, stated, "There’s a reason why it’s respiratory virus season. We’ve gotten so used to thinking about those really severe ones — like COVID, flu and RSV — but there are many other respiratory viruses that will make you sick."

Hamilton said that for common respiratory infections like HMPV, “a lot of the time, you’re going to get better on your own, but that’s not always the case.” She added, “Often, the infection is relatively mild, and we often think of it like a common cold. Many people don’t necessarily know that their common cold is caused by human metapneumovirus, but it’s definitely one of the viruses that’s often associated with the common cold.” Some common symptoms of an HMPV infection include coughing, fever, nasal congestion, and shortness of breath.

HMPV spreads in similar ways to some other respiratory viruses: through droplets produced by coughing or sneezing, and through touch, such as handshakes or touching contaminated surfaces. Harris said, “Simple measures can prevent transmission. Those measures are, if you are sick, if you have symptoms, stay home. Also, consider wearing a mask if you are in crowded or poorly ventilated spaces, when you are aware that viruses are circulating. Improve ventilation where you can. And of course, cover coughs and sneezes with a tissue.”

Harris said some people are at increased risk of developing severe infections from HMPV. She stated, “In some cases, like any common cold virus, it can lead to more severe disease in people who don’t have immunity or who have very weak immune systems. These are very young babies — which is why you don’t go and visit a newborn baby and kiss it when you have a cold — and very elderly people. Again, that’s why you shouldn’t go and visit your 90-something great-grandmother in the hospital when you have a cold.”

Health care providers can test for HMPV, but there is no vaccine, and there are no specific antiviral therapies to treat the infection. Resting at home and staying hydrated can help relieve symptoms, and some over-the-counter medications may also help. Mild cases of HMPV typically last a few days to a week, and many people recover on their own in two to five days. John Tregoning, a professor of vaccine immunology at Imperial College London, said in a statement released by the UK Science Media Centre on Monday, “It behaves the same as flu, SARS-CoV-2, RSV, and so the advice for those affected is the same — rest, hydrate, try not to spread it to others. See your GP if you feel very unwell. As it is a virus, antibiotics will not have any effect.”