Human metapneumovirus: Doctors say it’s the most important virus they’ve ever heard of

CNN
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Last winter was a tough one for respiratory viruses, dominated by a surge in respiratory syncytial virus, influenza and Covid-19. But just as the epidemic was winding down, a little-known virus was picking up steam that caused many of the same symptoms: lower lung infections, severe coughs, runny noses, sore throats and fevers.

A case of human metapneumovirus (HMPV) soared this spring, according to the U.S. Centers for Disease Control and Prevention’s Respiratory Virus Surveillance System.fulfilled hospital intensive care unit If you have young children or the elderly who are most vulnerable to these infections. At its peak in mid-March, almost 11% of specimens tested were HMPV-positive, a figure approximately 36% higher than the pre-pandemic average. peak season The test positive rate is 7%.

But most people who got infected probably didn’t even know they had it. Sick people usually don’t get tested outside of a hospital or ER. Unlike COVID-19 and influenza, there are no vaccines or therapeutic antivirals for HMPV. Instead, doctors treat severely ill people by addressing their symptoms.

Underestimated threat

According to research HMPV causes as much tragedy in the United States each year as influenza and a closely related virus, RSV. A study of patient samples collected over a 25-year period found it to be the second most common cause of respiratory infections in children after respiratory syncytial virus. A study conducted over four winters in New York found it to be as common as respiratory syncytial virus and influenza among hospitalized elderly. Like these infections, HMPV can lead to intensive care in the elderly and fatal cases of pneumonia.

Diane Lee Davison contracted human metapneumovirus during a family celebration in early April. Two weeks later she had a severe cough and was unable to speak on her phone.

“It was just a few words,” said Davison, 59, an entertainment attorney in Baltimore. “Sometimes I would cough so hard and hard that I literally felt like throwing up.”

Her cough was so constant and bad that she was convinced she had finally contracted it after she had managed to avoid it during the pandemic. However, she took six rapid tests for COVID-19, all of which came out negative.

Davison has been on guard throughout the pandemic because of his weakened immune system. Worried about pneumonia, he took an X-ray at a radiology clinic near his home and was told nothing was wrong.

However, doctors were not satisfied and sent her to the emergency room for further examination. Her blood test revealed that she had HMPV.

“I was like, ‘What? ‘ Because that sounds really dire,” Davison said. “It’s the first time I’ve heard of such a thing.”

Human metapneumovirus was discovered in 2001 by Dutch virus hunters. They collected 28 samples from Dutch children with respiratory infections of unknown origin. Some of the children were so sick that some required ventilators, but they tested positive for no known pathogens.

The researchers cultured samples with different types of cells from monkeys, chickens and dogs and looked at the cultures under an electron microscope. Something they seem to be structurally related to the Paramyxoviridae family, a group of viruses known to cause respiratory illnesses in people such as measles, mumps, and respiratory syncytial virus (RSV). I found

A detailed genetic study of this virus revealed that it is closely related to the avian metapneumovirus that infects birds. The new virus was named human metapneumovirus. Scientists believe they probably jumped from birds to humans at some point and evolved from there.

When researchers tested blood samples from 72 patients that had been stored since 1958, all showed evidence of exposure to the mysterious virus, allowing the virus to enter humans undetected for at least half a century. was shown to circulate.

doctor and patient in the dark

Respiratory infections are the leading cause of death in children worldwide and the leading cause of hospitalization in children in the United States, but scientists still don’t know what causes a significant portion of them, says pediatrician John Williams. says Dr. The University of Pittsburgh PhD has spent his career researching HMPV vaccines and treatments.

Williams said large-scale epidemiological studies were conducted to investigate the causes of respiratory infections in the 1950s and ’60s.

“Basically, we were only able to identify the virus in people about half the time. So the question was, ‘OK, what about the other half?’ “Human metapneumovirus doesn’t account for all of the unknown viruses, but it does account for a significant proportion, with roughly the same number of cases as RSV and influenza.”

But no one knows about it. Williams calls it “the most important virus we’ve ever heard of.”

“These are the big three viruses,” he said. “Those are the big three.” It is children and adults who are most likely to send people to hospitals and cause serious illness, and it is most likely to storm nursing homes and make the elderly really sick and even dead. ”

Testing for HMPV is rarely done outside hospitals, making it difficult to know the true burden of the disease.

Blood tests show that most children are infected by the age of five.

2020 study The Lancet Global Health estimated that in 2018, more than 14 million children under the age of five were infected with HMPV, more than 600,000 were hospitalized, and more than 16,000 died. there is

However, humans are reinfected throughout their lives because infection results in weak or incomplete immune defenses.

Companies are working to develop a vaccine against it. Covid-19 vaccine maker Moderna has just completed early studies of mRNA vaccines against HMPV and parainfluenza, according to the website clinicaltrials.gov.

The CDC recommends that physicians consider testing for HMPV during the winter and spring, when HMPV infections peak.

Doctors don’t test for the virus largely because of a lack of awareness of the virus, but also because testing probably won’t change the care they give patients, Williams said. That would help rule out other causes that have specific treatments, such as the novel coronavirus or the flu.

Ms Davison said she suffered severe bronchitis from HMPV. She was hospitalized briefly for follow-up. She eventually got better, but she was sick for a month.

Of course, she’s had respiratory infections before, but she’s especially happy to be on the other side of the human metapneumovirus, she said. “This was really the worst thing I have ever experienced.”