Last winter, respiratory viruses made their presence especially noticeable with an outbreak respiratory syncytial virus (RSV), from flu and his corona virus. As they began to subside, a little-known virus appeared with many of the same symptoms (cough, runny nose, sore throat and fever).

Cases of metapneumovirus, or HMPV, have increased in the spring, according to the US Centers for Disease Control and Prevention (CDC). At a peak in mid-March, nearly 11% of samples tested positive for HMPV, up 36% from the pre-pandemic seasonal peak of 7% positive, CNN reports.

However, most people who got stuck probably didn’t even know they had them. Unlike Covid-19 and the flu, there is no vaccine or antiviral drugs to treat it.

Human metapneumovirus was discovered by Dutch doctors in 2001. They had 28 samples from children in the Netherlands with unexplained respiratory infections. Some of the children were very ill and needed mechanical assistance, but no known pathogens were identified.

The researchers cultured the samples in a variety of monkey, chicken and dog cell types and then examined the cultures. They saw something that looked structurally related to the paramyxovirus family, a group of viruses known to cause respiratory illnesses such as measles, mumps, and respiratory syncytial virus.

A closer look at the genes revealed a close relative: an avian metapneumovirus that infects birds. Scientists believe that at some point it probably passed from birds to humans and evolved from there.

“Respiratory infections are the leading cause of death in children worldwide and the #1 cause of hospitalization in the United States, but scientists don’t know what causes most of them,” says Dr. John Williams. pediatrician at the University of Pittsburgh who has dedicated his career to researching vaccines and treatments for HMPV.

Williams says that extensive epidemiological studies were conducted in the 1950s and 1960s to look at the causes of respiratory infections.

“Essentially, they could identify the virus in humans about half the time. And so the question was, “OK, what about the second half?” he reported.

But nobody knows this. Williams calls it “the most important virus you’ve never heard of”.

“Those are the three main viruses,” he said. “These are the three most important factors for children and adults that are most likely to lead to hospitalization of people and cause serious illness, most likely to end up in nursing homes and make older people seriously ill and even kill them.”

According to CNN