A common but sometimes serious respiratory virus is spreading at unseen rates among young people in the United States, overwhelming children’s hospitals.

RSV (respiratory syncytial virus) is a common cold virus that usually has mild symptoms. Most children catch it before they are two-years-old and have a non-threatening reaction, according to the CDC.

It consists of common cold and flu symptoms and goes away after one to two weeks.

But increasingly, children are coming down with severe cases of RSV that have been seen across the US, CNN reported.

These children experience dehydration, trouble breathing, and even pneumonia or bronchiolitis. They end up in emergency wards and are hospitalized.

The increase in severe RSV cases in American children is being described as “unprecedented,” according to the report. Premature babies, newborns and children with weakened immune systems or lung and heart conditions are considered high risk for the virus.

A sick child who is hospitalized generally needs to have extra oxygen and in rare cases has to be hooked up to a ventilator to have help breathing.

The CDC said on Thursday that RSV is on the rise across the country, with children’s hospitals busier than they’ve been in two years. US Department of Health and Human Services data showed that three-quarters of paediatric beds are currently in use compared to the usual average of around two-thirds.

(Israel National News' North American desk is keeping you updated until the start of Shabbat in New York. The time posted automatically on all Israel National News articles, however, is Israeli time.)