Hundreds of children are showing symptoms of a rare respiratory illness, hospitals in at least 10 states report, and the CDC is investigating whether the trend could be an unprecedented outbreak of enterovirus D68.

Where is it?

About 475 children have been treated at Missouri’s Children Mercy Hospital in Kansas City, at least 60 of whom are in intensive care, according to a spokesman (CNN). The CDC confirmed at least 19 cases of enterovirus D68 were found at the hospital.

The Children’s Hospital Colorado in Denver told the Denver Post that more than 900 children have been treated for respiratory illnesses in the past three weeks, including 86 admitted to the hospital. At least five children at Rocky Mountain Hospital have been admitted to intensive care, but the CDC has not yet confirmed D68 in Colorado yet.

The CDC also confirmed 11 cases of the virus in Chicago, with patients ranging between 20-months-old to 15, and eight of whom with a history of asthma. The city’s hospitals have treated dozens of children with respiratory symptoms, and a University of Chicago spokesman told a local CBS affiliate that it was “as if winter flu season is starting early”.

No one has died from the outbreak in any state.

What is the CDC doing?

Anne Schuchat, director of the CDC’s center for immunization and respiratory diseases, told reporters “the situation is evolving quickly,” and that new outbreak clusters would not be surprising. Mark Pallansch, the CDC’s viral disease division director, said the agency was looking into underlying causes: “It’s not highly unusual but we’re trying to understand what happened this year in terms of these noticeable and much larger clusters of severe respiratory disease.”

Pallansch told CNN that the high number of reported hospitalizations could be “just the tip of the iceberg”. The states that have contacted the CDC are Missouri, Illinois, Colorado, Kansas, Oklahoma, Iowa, Kentucky, Ohio, North Carolina and Georgia.

What is enterovirus D68?

Enteroviruses are extremely common and most show no symptoms or resemble a mild cold. The D68 strain, though known since 1962 and related to the rhinovirus that causes the common cold, is relatively rare – or at least “very rarely reported”, in Schuchat’s words.

The virus’ most pronounced symptoms are wheezing, coughing and trouble breathing; fever, sneezing and cold-like symptoms are also possible. The virus also exacerbates asthma and pre-existing respiratory trouble, but it rarely affects adults. The rapid pace of symptoms also differentiates the virus from the common cold.

What does it feel like?

A 13-year-old from Colorado told a local ABC affiliate that “My head started hurting and after that my lungs started closing up. It felt different.” Several parents reported to local news that their children suddenly had trouble breathing, faces went “white as a ghost” and lips “turned blue”. Schuchat said “most of the runny noses out there are not going to be turning into this.”

How is it treated and prevented?

Most patients recover quickly and on their own – treatments for the common cold often help, but it is a person’s immune system that actually beats the virus. Most children recover after about a week. Should a patient suffer severe respiratory trouble, doctors will facilitate breathing with intubation, if necessary.

There are no vaccines and antibiotics have no affect on viruses, but flu shots and other preventative measures should help. As with many viruses, D68 transmits easily, by way of coughing and contact with sick people or surfaces.

Prevention is a simple as common sense during flu season: wash your hands thoroughly; avoid physical contact with sick people or stay at home if you feel ill; cough and sneeze with a hand over your moth; avoid touching your eyes, nose and mouth with dirty hands; clean surfaces, especially doorknobs; and closely monitor asthma symptoms, if you or others have it.