Will Cornejo, 13, recovers at Rocky Mountain Hospital for Children at Presbyterian/St. Luke’s Medical Center in Denver from what doctors suspect is enterovirus 68. (Cyrus McCrimmon/Denver Post)

Scores of children in at least a dozen states are afflicted by a severe respiratory illness, with at least six states confirming the presence of a rare virus strain in children as young as six weeks old, public health officials say.

Hospital officials in Chicago and Kansas City, Mo., reached out to the CDC last month after the number of people needing care for severe respiratory illnesses was “higher than expected for this time of year,” Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases, said Monday.

Testing confirmed that patients in several of these states had a rare enterovirus strain that primarily leads to difficulty breathing, rather than rashes or neurological issues. Enteroviruses are incredibly common, with more than 100 strains leading to between 10 and 15 million infections each year, the CDC said. This rare strain, known as enterovirus 68, has been identified before in the U.S. and other countries, but it is fairly uncommon, Schuchat said during a conference call with reporters.

Other states are also investigating clusters of severe respiratory illness reports to see if this same strain is cropping up, the CDC said. About a dozen states in total had contacted the CDC by Monday, Schuchat said. The virus was confirmed to be in at least six states, according to the CDC and state health officials: Missouri, Illinois, Iowa, Kentucky, Colorado and Kansas. There are also suspected cases in Alabama, Georgia, Michigan, Oklahoma, Ohio and Utah, the CDC said Monday.

“We’re in a stage where it’s difficult to say just how big this is, how long it will go on for and how widespread it will be,” Schuchat said during a conference-call with reporters.

One hospital in Kansas City, Mo., reported treating nearly 500 children — ranging from six weeks old to 16 years old — for respiratory illnesses. Mary Anne Jackson, director of the infections diseases division at Children’s Mercy Hospital, said the “unusually severe outbreak” saw a surge that included dozens of children requiring care each day and required the hospital to open up new beds to treat everyone.

“It’ll be interesting to see what happens over time, because the way this virus spreads, kid to kid, it’s likely if it’s in 12 states it will be in more than 12 states over the next several weeks,” she said.

Jackson said that she believes that between 70 and 90 percent of the children treated at Children’s Mercy had this particular strain. Still, she said there is no need for public panic, because the majority of illnesses that will crop up will be like a “low-grade, common cold.”

There is no vaccination for this virus.

“Many people with this kind of respiratory virus will do well with time,” Schuchat said, adding that the virus typically lasts for about a week.

Most enterovirus infections in the U.S. occur in the summer and fall, so the timing of these infections are not unusual, Schuchat said. But the particular strain and the number of infections is unusual. In addition, children facing this strain could be wheezing or having difficulty breathing, a fairly clear sign that they need medical help.

“Most of the runny noses out there are not going to be turning into this,” she said

The only confirmed cases of this rare strain have been found in children, she said. More than half of the children confirmed to have this enterovirus strain in Kansas City and Chicago have a history of asthma or wheezing, which is why public health officials are urging extra care with children who have asthma.

On Monday, other states confirmed cases of the rare strain. Ann Garvey of the Iowa Department of Public Health said that the CDC confirmed samples sent from the state showed the strain. “It’s leading us to believe that we likely have some transmission statewide,” Garvey said, though she noted that so far health-care providers have not reported an overwhelming number of cases.

Health care officials in Colorado and Kentucky also told The Post on Monday that CDC testing had revealed that the virus was appearing in those states.

In Illinois, nearly a dozen specimens from a Chicago hospital tested positive for this strain. There have been increased reports of respiratory illnesses elsewhere in the state, but they have not been tested for the enterovirus strain, according to Melaney Arnold of the Illinois Department of Public Health.

Last month, 141 children from Kansas were treated at Children’s Mercy Hospital in Missouri and tested positive for either a rhinovirus or enterovirus; some of these children also tested positive for the rare strain of enterovirus, Aimee Rosenow, a spokeswoman for the Kansas Department of Health and Environment, told The Post.

States without any confirmed cases also remain on the lookout. While Ohio had no confirmed cases as of Monday, it did have potential cases across the state that required hospitalizing children, said Melanie Amato, a spokeswoman for the state Department of Health. The department is working with children’s hospitals in Cleveland and Cincinnati to send samples to the CDC and expects that some could come back positive.

“So far, we have not had any confirmed cases,” said Zack Moore, medical epidemiologist with the North Carolina Department of Health and Human Services. “But we don’t know what the future will hold, so we’re monitoring it very closely.”

Moore said that the reason this strain is worrisome is because it has been linked to clusters of illnesses, popping up in groups of infections.

The enterovirus 68 strain was first isolated in 1962 in California. While it has been rarely seen since then, it has cropped up in clusters and has been blamed for three deaths in the Philippines and Japan in recent years. Between 2009 and 2013, the National Enterovirus Surveillance System showed 79 reports of this strain, the CDC said.

Earlier this year, up to two dozen children in California were believed to be suffering from a polio-like illness. A report found that two of the five children tested positive for enterovirus 68; doctors noted that the exact symptoms varied in the five children.

Related: What is Enterovirus 68?