Human Metapneumovirus Finally Taken Seriously

Like many other respiratory viruses, Williams says, hMPV affects those with chronic lung disease or pre-existing conditions such as asthma and cancer. But even so, he says, many doctors don’t know it’s a threat because, until relatively recently, no one tested it outside of academic research.

“There’s no doubt that many doctors, even in the medical community, don’t know how common hMPV is,” he said. “As clinical tests became more available, people were surprised to say to me, ‘There was a patient with metapneumovirus in the ICU last week.’ It’s real and I never believed it before.” Until people see it for themselves, I think they don’t fully believe in the cargo.”

Vermund says it’s likely that there have been spikes in hMPV infection 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 the number of hMPV cases is being detected by epidemiologists for the first time.

“The Chinese are quite advanced in molecular diagnostics of respiratory viruses, and they do more public health surveillance than many other countries,” he said. “I think what we’re seeing is that they’re doing a particularly good job at that, and so we’re finding that metapneumovirus is more prevalent than we previously realized.”

Williams believes that the current surge of interest in hMPV could have positive public health implications. Currently, he said, hMPV can only be detected as part of a multiplex panel, a diagnostic that tests for the presence of up to 25 different respiratory viruses, and costs about $200 per patient. While this is a worthwhile investment for emergency physicians deciding whether to admit or send a sick baby home, such costs are often prohibitive for general practitioners.

“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 many viruses and is difficult for the average clinician to capture.”

There are hopes that a low-cost test for hMPV could be on the way. According to Vermund, the Ragon Institute in Massachusetts is working on ways to try to lower the cost of a respiratory virus test below $6 per patient, with the ultimate goal of lowering the cost to below $1.

Likewise, another consequence of increased awareness of hMPV is that it provides stronger incentives to fast-track vaccination. There is currently no licensed vaccine against the virus, but a number of candidates have been introduced early stage clinical trials in the last two years.

Last summer, scientists from the University of Oxford began clinical trials Adding hMPV to existing vaccines would be the most practical means of spreading additional immunization, says Andrew Pollard, professor of infection and immunity, who leads the RSV and hMPV vaccine in partnership with Moderna and leads the Oxford Vaccine Group.

“If you can put them in the same vaccine as RSV and hMPV, you’re actually covering more of those who come into the hospital by inhalation without needing extra shots,” Pollard says. “But before we do that, we need to find out how often you should vaccinate against hMPV. “If you can provide immunity by vaccinating every few years, then you can combine it with RSV.”

Overall, Vermund describes the sudden interest in hMPV as an important development. Although the virus has not caused the next pandemic, it still affects so many people that it takes a heavy toll on public health systems, as well as a long-unrecognized cause of death in vulnerable people.

“While not one of the deadliest viruses, metapneumovirus is incredibly common,” he says. “It causes a non-trivial amount of colds over the years, it’s an incredible economic burden, and every once in a while it kills a person.”