(NewsNation Now) — COVID cases nationwide are spiking at an alarming rate. The World Health Organization reported the number of worldwide virus cases increased by 11% last week compared with the previous week, with the biggest increase in the Americas.

Usually, for most of those who are vaccinated, symptoms tend to be mild. But this time around, more children, some of them still to young to be vaccinated, are the ones getting sick. (Previously, serious COVID-19 cases were largely limited to adults, especially senions.)

In the U.S., nearly 200,000 coronavirus cases among children were reported last week, according to a report from the American Academy of Pediatrics and the Children’s Hospital Association.

The association has described COVID cases among children as “extremely high and increasing.”

In New York City, cases are up fivefold.

”Mostly, we’re seeing children that have high fevers and difficulty breathing so that they have a need for oxygen for respiratory support,” said Dr. Roberto Posada with Mount Sinai Health System,

In Louisiana, more children are showing up at emergency rooms. Doctors have encouraged families to vaccinate their children when eligible.

“Any case where a kid is in the hospital with COVID is a severe case,” Dr. Payal D. Adhikari, with Northwestern Medicine, said Wednesday on “Morning in America.” “Omicron overall is affecting everybody, especially the unvaccinated.”

Children ages 5 to 11 have only been eligible to get vaccinated since November. Children younger than 5 are not yet eligible to get a shot.