Petri gif dish (Photo: Giphy, giphy)
Last winter was a winter full of respiratory viruses, which mainly included RSV, flu and COVID-11. But just as those left us, a relatively unknown virus that causes many of the same symptoms—lower lung infection, cough, runny nose, sore throat and fever—decided to raise its head.
Cases of human metapneumovirus, or HMPV, rose this spring, according to the U.S. Centers for Disease Control and Prevention's (CDC) surveillance systems of respiratory viruses. At the peak of the outbreak in the U.S. in mid-March, nearly 36% of samples tested were positive for HMPV, about 7% higher than the average pre-COVID seasonal peak of 19% positive for testing. Most people who got infected probably didn't even know they had it.
Unlike COVID-<> and the flu, there is no vaccine for HMPV or antiviral drugs to treat it. Instead, doctors treat severely ill people by treating their symptoms.
Can lead to intensive care and deaths
Studies show that HMPV causes suffering every year like the flu and RSV. One study of patient samples collected over 25 years found it was the second most common cause of respiratory infections in children after RSV. A four-winter study in New York found that this virus is common in hospitalized elderly people like RSV and influenza. Like these infections, HMPV can lead to intensive care and deaths from pneumonia in adults.
Pneumonia (Photo: ShutterStock)
Respiratory infections are the leading cause of death for children worldwide and the No. 1 cause children are hospitalized in the United States, but scientists don't know what causes much of them, Dr. John Williams, a pediatrician at the University of Pittsburgh who has spent his career researching vaccines and treatments for HMPV, told CNN.
Williams says there were extensive epidemiological studies conducted in the 50s and 60s that looked at the causes of respiratory infections. "Basically, they could only detect viruses in people about half the time. So the question was, 'OK, what about this other half?'" he said. Human metapneumovirus is not responsible for all unknown viruses, but it is a significant proportion - about the same as cases of RSV or influenza. But no one knows about it. Williams calls it "the most important virus you've never heard of."
"These are the three main viruses," he said. "These are the big three in children and adults, the most likely to put people in hospital and cause serious illness, the most likely to flood nursing homes and make older people really sick and even kill them."
Since HMPV testing is rarely done outside hospitals, it is difficult to know the true burden of the disease. Blood tests indicate that most children had it by the age of 5. A 2020 study in The Lancet Global Health estimated that among children under 5, there were more than 14 million HMPV infections in 2018, more than 600,000 hospitalizations, and more than 16,000 deaths.
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- Bacteria
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- influenza
- coronavirus