Human metapneumovirus is finally being taken seriously

Like many other respiratory viruses, Williams says hMPV tends to impact those with chronic lung disease or existing conditions such as asthma and cancer. But despite this, he discovered that many doctors do not know that it is a threat, largely because until recently, no one has tried it outside of academic studies.

“There is no doubt that even in the medical community, many doctors are not aware of how common hMPV is,” he says. “As clinical evidence has become more available, I’ve had people tell me, with surprise, ‘I had a patient in my ICU with metapneumovirus last week. It’s true, and I never believed it before. Until people see themselves, I don’t think they totally believe in weight.

Vermund says that there have probably been several peaks of hMPV infections in the past, but either we were not aware of them or we confused them for influenza. He explains that one of the consequences of Covid has been the recognition of the need for greater vigilance of circulating respiratory viruses, meaning that the numbers of hMPV cases have been detected by epidemiologists for the first time.

“The Chinese have become quite advanced in molecular diagnostics for respiratory viruses and do a lot of public health surveillance, more so than many other countries,” he says. “I think what we can see is that they are doing an especially good job at this, and thus finding that the metapneumovirus is more common than we realize.”

Williams believes that the current spike in interest in hMPV could have positive consequences for public health. Now, he says hMPV can only be detected as part of a so-called multiplex panel, a diagnosis that checks for the presence of up to 25 different respiratory viruses, at a cost of about $200 per patient. While this is a worthwhile investment for emergency physicians who decide whether to admit a sick child or send him home, such costs are often prohibitive for ordinary physicians.

“There are inexpensive tests for influenza, Covid, and RSV that can be used by clinicians everywhere,” he says. “But there’s really no cheap test for hMPV, just this complex diagnostic panel that evaluates many viruses and it’s hard for the average clinic to get.”

There are hopes that low-cost tests for hMPV could be on the way. According to Vermund, the Ragon Institute in Massachusetts is working on ways to try to reduce the price of respiratory virus tests to less than $6 per patient, with the ultimate goal of reducing the cost to less than $1.

Equally, another consequence of the growing awareness surrounding hMPV is that it provides stronger incentives for the speed of a vaccine. So far, no licensed vaccine is available for the virus, but a series of candidates have entered early phase clinical trials in the last two years.

Last summer, scientists from the University of Oxford launched a clinical trial of a combined RSV and hMPV vaccine in partnership with Moderna, and Andrew Pollard, a professor of infection and immunity who heads the Oxford Vaccine Group, says adding hMPV to existing vaccines would be the most practical means of spreading additional immunization .

“If you can put in the same vaccine, so RSV and hMPV, then without needing extra needles, it actually covers more of the respiratory admissions in the hospital,” says Pollard. “But before we can do that, we need to know how often you need to vaccinate against hMPV. If you can provide immunity by vaccinating every few years, you can combine it with RSV.”

Overall, Vermund describes the sudden interest in hMPV as an important development. While the virus will not cause the next pandemic, it still afflicts such a significant number of people that it is a major drain on public health systems, in addition to being a long-underreported cause of mortality in the vulnerable.

“Although metapneumovirus is not one of the most lethal viruses, it is incredibly common,” he says. “It has caused a non-trivial amount of colds over the years, which is an incredible economic burden, and every once in a while, it kills someone.”