Rumors of school closures in the Chinese city of Wuhan, as well as Beijing’s acknowledgment of a rise in cases of human metapneumovirus (hMPV), have sparked understandable concern. However, although some draw parallels to the early days of COVID-19, human metapneumovirus is not a new virus and is unlikely to trigger the next pandemic.
The human metapneumovirus was first discovered in 2001 by Dutch virologists who sought to explain various respiratory infections seen over the decades but which could not be attributed to any known pathogen. By analyzing nasal swabs taken from 28 children who had such infections over the past 20 years, they isolated a previously unknown paramyxovirus. This large family of viruses also includes respiratory syncytial virus (RSV), human parainfluenza, measles and mumps.
“Although hMPV mutates and evolves over time, with new strains emerging, it is not a virus that we consider to have pandemic potential. »
– Dr Andrew Catchpole, virologue
Respiratory virus
The virus, which they named human metapneumovirus (hMPV), causes symptoms similar to respiratory syncytial virus (RSV), ranging from mild breathing problems to severe coughing, bronchiolitis (inflammation of the small airways in the lungs), and pneumonia. Often, patients also experience high fever, muscle pain and vomiting. Following a pattern reminiscent of RSV, “very young children infected with hMPV appear to require hospitalization and mechanical ventilation,” the researchers said.
After identifying this virus, researchers tested blood samples from other Dutch children, including historical samples. Their analyzes found that almost all children had antibodies to hMPV before the age of five – a sign of previous exposure – and showed that the virus had been circulating in humans for at least 50 years.
Subsequent studies have confirmed that human metapneumovirus is a common respiratory virus that circulates in many countries in winter and spring. People of all ages can be infected and reinfected throughout their lives. While some end up in hospital with bronchitis or pneumonia, most experience symptoms similar to a cold or flu – including cough, fever, nasal congestion and shortness of breath – and recover. in a few days. Young children, the elderly and those with weakened immune systems are most at risk of developing a severe form of the disease.
Cases in China
According to data released by the Chinese Center for Disease Control and Prevention, which tracked health data through December 29, 2024, a continued upward trend in respiratory viral infections was observed. This includes seasonal influenza, rhinovirus, RSV and human metapneumovirus, particularly in the northern provinces of China, during the last weeks of the year.
“The observed increase in respiratory pathogen detections is within the expected range for this time of year, during the Northern Hemisphere winter,” the World Health Organization (WHO) said. “WHO is in contact with Chinese health officials and has not received any reports of unusual outbreak patterns. »
“Chinese authorities report that the health system is not overwhelmed and that no emergency declaration or exceptional response has been triggered. »
Other temperate countries in the northern hemisphere have also reported an increase in influenza-like illnesses and/or acute respiratory infections in recent weeks, consistent with usual seasonal trends.
Although more information on the specific strain circulating in China would be helpful, “there is, so far, no evidence that what is observed in China is significantly different from what is observed in Europe.” It appears to be a combination of several common winter viral infections, rather than a new or unknown virus,” said Professor Peter Openshaw, a respiratory specialist and immunologist at Imperial College London, UK. United.
Low pandemic potential
A key difference from SARS-CoV-2, which causes the COVID-19 pandemic, is that the human metapneumovirus has been around for decades, and most people have some pre-existing immunity to it.
“Although hMPV mutates and evolves over time, with new strains emerging, it is not a virus that we consider to have pandemic potential. This is because changes in hPVD are gradual and based on strains that are already present,” explained Dr Andrew Catchpole, virologist and scientific director at hVIVO, a UK organization specializing in clinical trials of HPV vaccines. infectious and respiratory diseases.
“Pandemics occur when a completely new virus enters the human population, such as COVID-19, or, in the case of influenza, when a completely new variant of the virus arises from a combination of human versions and animals, emerges from what we call the animal reservoir. No animal reservoir of related viruses is known for hMPV. »
Prevent infection
Although the risk of a metapneumovirus pandemic is low, the virus can cause serious illness in some people and unpleasant symptoms in many others. In the absence of a vaccine to prevent human metapneumovirus or specific antiviral treatment, the best strategy is to try not to catch it.
Since the virus is spread through coughing and sneezing, or through contact with contaminated objects, surfaces, or hands, the risk of contracting or transmitting it can be reduced by taking precautions similar to those that prevent the spread of others respiratory pathogens, such as influenza.
This involves staying home if you have symptoms, wearing a mask in crowded or poorly ventilated spaces, covering your mouth and nose with a tissue or the crook of your elbow when coughing and sneezing, and washing your hands regularly. hands with soap and water. “People at high risk or with complicated or severe symptoms should seek medical attention as soon as possible,” the WHO said.
