The Centers for Disease Control and Prevention revealed there are 664 confirmed cases of enterovirus-68 in 45 U.S. states and the District of Columbia Wednesday. There has been a nationwide outbreak of the virus, which is also referred to as EV-D68, which is associated with severe respiratory illness.

The 664 number corresponds with a mid-August to Oct. 8 timeframe, the CDC said. There is at least one case of EV-D68 in each of the states listed, but just how widespread the infections are in each state wasn't revealed.

Enteroviruses typically circulate in summer and fall, the agency wrote. It’s expected that the number of cases will dwindle later in the fall.

Practically all of the confirmed cases of EV-D68 infection have been among children,  most of whom have a history of asthma or wheezing.

The respiratory disease has led to the death of at least one child a month. School districts are spreading awareness about the polio-like illness.

Dr. Emmanuelle Waubant, a neurologist at the UCSF Benioff Children’s Hospital in California, said many of the enterovirus-68 cases are “just as benign as the common cold.”

“It’s probably a little out of proportion compared to what it should be,” she said. “Because of all the fear that has been raised by these upper respiratory viral infections hitting the U.S., it’s important to keep everything in perspective. The number of kids [with enterovirus-68] that have been counted in the U.S. is not concerning at this point.”

The CDC does not have a definite reason why there has been a drastic rise in the number of cases. “This increase could be caused by many different viruses that are common during this time of year,” the agency said. “EV-D68 appears to be the predominant type of enterovirus this year and may be contributing to the increases in severe respiratory illnesses.”

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