Like many other respiratory viruses, Williams says hMPV tends to affect people with chronic lung disease or existing illnesses such as asthma and cancer. But despite this, he found that many doctors are unaware that it is a threat, largely because until relatively recently, no one tested for it outside of academic studies.
“There is no doubt that even within the medical community, many doctors are simply unaware of how common hMPV is,” he says. “As clinical testing has become more available, people have said to me, in surprise, ‘I had a patient in my intensive care unit with metapneumovirus last week.’ It’s real, and I never believed it before. Until people see it themselves, I think they don’t fully believe this burden.
Vermund says there were probably many spikes in hMPV infections in the past, but we either weren’t aware of them or mistook them for the flu. He explains that one of the consequences of Covid has been the recognition of the need for greater surveillance of circulating respiratory viruses, meaning that cases of hMPV are being detected for the first time by epidemiologists.
“The Chinese have become very advanced in molecular diagnostics of respiratory viruses and they do a lot of public health surveillance, more than many other countries,” he says. “I think maybe what we’re seeing is that they’re doing a particularly good job in this area, and so they’re finding that metapneumovirus is more common than we thought.”
Williams believes that the current surge in interest in hMPV could have positive consequences for public health. Currently, he says hMPV can only be detected as part of a so-called multiplex panel, a diagnostic that checks for the presence of up to 25 different respiratory viruses, at a cost of about $200 per patient. Although a worthwhile investment for emergency room doctors deciding whether to admit or send a sick infant home, these costs are often prohibitive for ordinary doctors.
“There are inexpensive tests for flu, Covid and RSV that can be used by clinicians anywhere,” he says. “But there really isn’t a cheap test for hMPV, just this complex diagnostic panel that evaluates multiple viruses and it’s difficult for the average clinic to obtain.”
It is hoped that low-cost testing for hMPV could be on the way. According to Vermund, the Ragon Institute in Massachusetts is working on ways 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.
Similarly, another consequence of growing awareness of hMPV is that it provides stronger incentives to accelerate vaccine development. Currently, no approved vaccine is available against the virus, but a series of candidates have undergone preliminary clinical trials over the past two years.
Last summer, scientists at 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 directs the Oxford Vaccine Group, says adding hMPV to existing vaccines would be the most practical way to roll out additional vaccination.
“If you can deliver them in the same vaccine, so RSV and hMPV, then without needing additional needles, you’re actually covering a larger portion of respiratory hospitalizations,” Pollard says. “But before we can do that, we need to figure out how often you should get the hMPV vaccine. If you can provide immunity by vaccinating every few years, then you could combine RSV.
Overall, Vermund describes the sudden interest in hMPV as an important development. Although the virus will not trigger the next pandemic, it continues to affect such large numbers of people that it represents a major burden on public health systems, in addition to being a long-underestimated cause of mortality among vulnerable people.
“Even though metapneumovirus is not one of the deadliest viruses, it is incredibly common,” he says. “It has caused a fair number of colds over the years, which is an incredible economic burden, and every once in a while it kills someone.”
