The news: Forget your fears of Ebola coming to America — there's already a major virus sweeping the nation.

A mysterious outbreak of a respiratory disease thought to be Enterovirus 68 (EV-68) has spread from its original nexus in the Midwest to at least 38 states in the past several months. Thousands of children have visited emergency rooms, many so sick that they required hospitalization.

From Aug. 18 to Sept. 24, Children's Hospital Colorado alone had treated some 3,600 patients suspected of harboring the virus, and up to 10% needed to be treated for difficulty breathing. At Children's Hospital of Pittsburgh, the New York Times claims that up to 50 to 70 additional cases of respiratory disease among children than normal have arrived per day. Other regions facing the outbreak include Bridgeton, Mo., where SSM Cardinal Glennon has reported 800 cases, San Diego, Boston, Jackson, New York City and Chicago.

The mystery: The New York Times reports that the outbreak is "baffling" infectious disease experts, who have not yet come to any solid conclusions on why this particular strain of EV-68 has suddenly swept across the country. While enteroviruses in general are very common, EV-68 infection is normally quite rare — or at least, it's flown under the radar for epidemiologists. The CDC had only confirmed 100 causes in the U.S. between the 1960s and 2014.

While the infection hasn't resulted in any fatalities, the Washington Post reports EV-68 is causing severe symptoms like "coughing, wheezing and low blood oxygen levels (also known as hypoxemia)." Doctors advise that parents be alert and cautious, since the most serious cases may require admission:

...there are signs that a child requires immediate medical care: rapid or labored breathing that involves neck muscles, wheezing, complaining of chest pain or not being able to catch one's breath, and blue lips. A baby who has to stop drinking from a bottle to breathe should be seen by a doctor. A fever need not be present.

Jennifer Cornejo told Denver's 7News that her 13-year-old son "was in really bad shape. He came really close to death. He was unconscious at our house and white as a ghost with blue lips — he just passed out."

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No fatalities yet. The good news is that although EV-68 spreading rapidly, it is unlikely that anyone is going to die or suffer lasting complications. It primarily causes complications in young children with a history of asthma or wheezing, and it tends to be very mild in adults. Children's Mercy Hospitals and Clinics infectious disease director Dr. Mary Anne Jackson told Yahoo! News that some suspected cases of EV-68 may just be the first strains of the upcoming winter flu season.

Still, EV-68's national tour has persisted beyond expectations. In early September, Vanderbilt University infectious disease expert William Schaffner told NBC that he hoped it would clear within a week. Sen. Chuck Schumer (D-N.Y.) wants the CDC to become more involved, providing medical supplies and implementing a better tracking system.

"From the perspective of what causes respiratory disease outbreaks, it's fascinating," Infectious Diseases Society of America spokesman Dr. Andrew Pavia told MedPageToday. "Scientifically, it's kind of a big deal."