January 6, 2025
4 minute read
HMPV cases are on the rise across Asia, but experts say there’s no need to panic
A common respiratory virus called human metapneumovirus (HMPV) is prevalent in some countries in Asia, including China, India, Malaysia, and Kazakhstan. Here’s what we know
Human metapneumovirus particles.
Brian Megson, Health Protection Agency Infectious Diseases Center/Scientific Source
Cases of a common respiratory virus called human metapneumovirus (HMPV) are surging in several Asian countries, but experts say the situation raises concerns about a larger global health threat. It is argued that this should not be caused. HMPV is classified as a winter infection, along with influenza and respiratory syncytial virus (RSV), and epidemics often peak during this time in the Northern Hemisphere. Common HMPV symptoms, such as a runny nose, cough, and fever, are usually mild. However, young children, the elderly, and people with weakened immune systems may be at higher risk of severe illness.
In mid-December 2024, Chinese health authorities reported an overall increase in respiratory infections, including an increase in HMPV in children under 14 years of age in northern China. Reports of an influx of infected people in hospitals have heightened the alarm and attention to this little-known but common winter respiratory disease.
“There is a fairly large outbreak of human metapneumovirus in Asia, and you could call it an epidemic,” says William Schaffner, an infectious disease physician and professor at Vanderbilt University Medical Center. “There is no need to panic. But for people in high-risk groups, now is the time to be careful.”
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Due to China’s relatively high number of infections, the country and neighboring countries have stepped up surveillance. Infected cases have also been confirmed in Malaysia, India, and Kazakhstan. But experts say HMPV has been occurring in humans around the world for decades.
John Williams, a pediatrician and professor of infectious diseases at the University of Wisconsin-Madison, said: “This virus has been around for at least 60 years, and genetic evolution studies suggest it evolved from an avian virus 200 to 400 years ago. This suggests that they have diverged.” I have been studying HMPV for over 20 years. “HMPV, like the more widely recognized influenza virus and RSV, causes periodic seasonal outbreaks each year. A typical HMPV season is late winter to early spring. Therefore, this is completely It’s not unexpected.”
Williams said widespread population immunity should lower the risk of larger public health problems. Schaffner added that travelers from countries with high HMPV rates “could potentially bring the virus into the United States, but the virus is already here.”
The United States experiences seasonal spikes every year. The U.S. Centers for Disease Control and Prevention currently reports a slight increase in HMPV in the country. However, the number of infections remains low, with nearly 2 percent of diagnostic tests coming back positive for the virus as of the week of Dec. 28. Last year, HMPV peaked in April, with about 8% of tests coming back positive.
Scientific American spoke with Schaffner to learn more about the recent HMPV outbreak, common symptoms, and people who are more likely to become seriously ill.
(An edited transcript of the interview follows below.)
What is HMPV?
Human metapneumovirus is also a winter respiratory virus in the same family as RSV and increases during this time of year (in the northern hemisphere). The virus affects the nose, throat, and chest and is easily transmitted from person to person. Although researchers have been keeping an eye on this virus for some time, it hasn’t been as well known to both the medical community and the general public because it doesn’t have the prominence of, say, influenza or the new coronavirus. It is also relatively unknown because there is no easy and widely available diagnostic method. But now, not only hospitalized patients, but also patients attending clinics, can receive diagnostic tests fairly quickly. Therefore, doctors are making this diagnosis more often than before. Although this virus has received more attention than before, it has always been present.
What symptoms do you have?
Like other respiratory viruses, it can invade the bronchial tubes and cause stuffy nose, sore throat, and cough. Some people also develop pneumonia. We are most concerned about young children who have not been infected with the virus or have no immunity to the virus, frail elderly people with chronic underlying health conditions, and people with weakened immune systems.
What do we know so far about recent outbreaks and cases?
In Asia, human metapneumovirus has been occurring on a fairly large scale, and it may even be called an epidemic. Although it has been diagnosed here in the United States, influenza, COVID-19, and RSV are far more prominent at this time. We can make these diagnoses more accurately, so the more we look, the more we’ll find. I don’t think this is something we should be alarmed about. That’s certainly not a bad thing. And while it is true that some travelers (to countries with high HMPV infection rates) may bring the virus into the United States, the virus is already present. My concern right now is for the American people, who have seen a surge in influenza cases in recent weeks. Our hospitals and emergency rooms are full of really miserable and pretty serious cases of influenza. And the new coronavirus and RSV are still on the rise.
Are you concerned about a larger global outbreak or pandemic?
There is nothing new about this virus, so I don’t think it can be called a pandemic. Populations may grow in different parts of the world at different times, but as the saying goes, we are a global village. And obviously, these viruses don’t require passports, so they can all travel around the world and enter through human transportation alone. And here in the U.S. we see a tremendous amount of domestic travel during the holiday season. Large gatherings of people, family gatherings, parties, etc. This provided an environment for all these respiratory viruses to accelerate their spread.
How can I minimize my risk of HMPV infection?
There is no vaccine for human metapneumovirus. So what we can do is avoid people who are coughing or sneezing. If you are sick, do not go to school or work. Please stay home. If you cough or sneeze, do so into your elbow. Wear a mask if you go indoors to a crowded place. If you are truly in that high-risk group, consider practicing social distancing. Let’s wait until these viruses are over. Then you can go out. Therefore, social distancing and wearing a mask are very helpful, along with proper hand hygiene at all times.
