As director of one of the only laboratories in the world dedicated to human Metapneumovirus research, John Williams used to spend most of his time trying to convince skeptical doctors that the virus was real. So when the recent outbreak in northern China was met with widespread alarm, Williams smiled wryly. An infection forgotten by public health was finally taken seriously.
What is Metapneumovirus or hMPV?
hMPV was first identified 24 years ago, by a group of Dutch scientists seeking to better characterize the viruses responsible for acute respiratory infections. But in the years since, awareness of hMPV has been remarkably low, despite it being one of many endemic respiratory viruses that circulate around the world seasonally, along with influenza, Covid, and respiratory syncytial virus ( VRS). “In North America or the southern hemisphere, it circulates during the winter months and, in the tropics, during the rainy season. First, RSV appears, then comes a high peak of influenza, and finally, HPV. Normally one precedes the another,” explains Williams.
Sten Vermund, medical director of the Global Virus Network (GVN), an international coalition of medical virologists, emphasizes that this virus is not going to cause a pandemic on the level of flu or covid. Being highly infectious, it is so common that almost all children suffered from it by the age of 5, In most healthy infants and adults, hMPV presents as a mild cold. Furthermore, it does not mutate or evolve with the same magnitude as covid or flu; Although our immunity levels periodically increase or decrease depending on the level of exposure, our defenses do not have to fight new forms of the virus.
However, Williams’ hunch is that the recent spike in cases in China reflects the fact that childhood immunity levels in the country had fallen as a result of the “Zero Covid” policies, which the Chinese government implemented for almost three years to suppress SARS-CoV-2. “China maintained prevention measures for much longer than the rest of the world. When it opened up, the population was more susceptible, probably because of that, rather than because there was a particularly virulent strain of hMPV,” he explains.
The self-administered flu vaccine got the go-ahead from the U.S. Food and Drug Administration.
Not everything is covid and flu
According to the latest data from the Centers for Disease Control and Prevention (CDC), hMPV levels in the US are low. Although they account for less than 2% of weekly positive tests for respiratory viruses, compared to 19% for flu and 7% for Covid, the country also experienced a sudden post-pandemic surge in Metapneumovirus infections during the winter of 2022. 2023.
In early 2023, William received calls from surprised doctors across the country, describing hospitalized patients, mainly young children, people over 75 years of age or immunocompromised individuals, who had tested positive for hMPV. For the specialist, this was not unexpected. A decade earlier, he published a seminal article in the journal New England Journal of Medicinewhich showed that the virus was the second most common infection in hospitalized children, after RSV.
A previous study conducted in New York over four years and published in 2008 also found that hVMP was as common a cause of hospitalization in older adults as RSV or influenza, with similar rates of ICU admissions ( ICU) and mortality. Another national study of adults hospitalized with symptoms of pneumonia showed that hMPV was as common as RSV, almost like the flu.
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