As of Sept. 30, 41 states reported lab-verified cases of children infected with enterovirus 68, but severe respiratory problems are not the only thing that doctors are seeing of late. More reports are coming out of muscle weakness or symptoms of paralysis, and what's confusing health officials is it doesn't appear to always be associated with the virus.
In Colorado, there were nine cases where children had weakness or paralysis in the limbs, and a few children in Michigan and Missouri have shown similar symptoms as well.
The Centers for Disease Control and Prevention is investigating these polio-like symptoms because not all the children who exhibited the weakness tested positive for EV-68. Four of nine children tested in Colorado had the virus, while four others didn't and one wasn't tested.
This 2007 photo provided by the Children's Hospital Colorado shows the facility in Aurora, Colo. On Friday, Sept. 26, 2014, the CDC said it is investigating nine cases of muscle weakness or paralysis in children at the hospital, and whether the culprit might be enterovirus 68 which is causing severe respiratory illness across the country. (AP/Children's Hospital Colorado)
Officials don't know whether the virus caused any of the children's arm and leg weaknesses or whether it's just something else they coincidentally picked up.
While some of these cases occurred within the last two months — during the same period the nation has seen a wave of the severe respiratory illnesses linked to the virus — earlier this year about two dozen children in California were exhibiting polio-like symptoms.
KPIX-TV reported that researchers at the University of California, San Francisco and Stanford University studied five children with these symptoms at the time and only two of them had EV-68. The news station reported that the other children could not be tested for the virus because they had already received a certain amount of treatment.
Doctors at the University of California's Benioff Children's Hospital in San Francisco told KPIX that there has not yet been a direct association between EV-68 and cases of what they're calling "acute flaccid paralysis."
Watch the report:
Official symptoms of EV-68, as described by the CDC, include mild to severe respiratory problems, fever, nasal drip, cough, wheezing and body aches. A Michigan boy who tested positive for the virus was not brought to the hospital for respiratory problems though but for paralysis in his legs, the New York Times reported.
The CDC issued an advisory last week asking health officials to report any patients who are 21 years old or younger who are exhibiting "acute onset of focal limb weakness occurring on or after August 1, 2014" and a "spinal cord lesion largely restricted to grey matter" as seen on an MRI.
Mark Pallansch, director of the CDC's viral diseases division, told the Times that the a connection between the paralysis symptoms and EV-68 is a possibility but it's "not the only possibility."
According to the CDC, there have been no deaths attributed to EV-68. The CDC said that this is the middle of "enterovirus season" and that the number of infections are expected to decline as fall progresses.
The Associated Press contributed to this report.