A severe respiratory illness that has affected hundreds in the U.S. Midwest has spread to four more states and now has been reported in more than a dozen states across the country.

The Centers for Disease Control and Prevention reported on Thursday that enterovirus EV-D68 has turned up in New York, New Jersey, Connecticut and Virginia. At least one of the cases in New York was reported in New York City, according to NBC New York.

Two children, one in New Jersey and one from Long Island, N.Y., were admitted to the hospital with the illness. Both were treated and released, and both are expected to make full recoveries.

The case in Connecticut is murkier. Reports claim a child is being treated at Yale-New Haven Hospital, but officials haven't announced what town that child is from.

The Virginia State Health Department reported that it had tested 10 patients for EV-D68 and seven were found to have the illness, according to a report from Fox 8 in that state. Those seven patients are being treated at hospitals in Virginia.

More than 100 types of enteroviruses exist and they are common in the U.S., affecting around 15 million people in the U.S. each year. Most strains of the virus are accompanied by mild cold-like symptoms.

But EV-D68 is a rare and severe strain of the enterovirus -- founded in California in 1962 -- that puts infants and children at risk. No cure has been found. Most people who catch EV-D68 recover without medical attention, but those susceptible to respiratory illness should be taken to the hospital.

Health officials warn that anyone who has trouble breathing or sees a child who does should call a doctor.

Since the virus appeared a month ago, the CDC has confirmed more than 100 cases of EV-D68 across the country. Alabama, Colorado, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Missouri, Montana and Oklahoma all have patients who have tested positive for the virus.