Physicians have yet to identify the mysterious polio-like illness that has paralyzed more than 100 children across 34 states since last summer, according to a USA Today report.
The cases mark the largest outbreak of a paralysis-causing virus physicians have seen in years.
The original cases coincided with an outbreak of a severe respiratory illness caused by enterovirus D68 but the inconsistency of the presence of the virus, symptoms and varying forms of paralysis have kept physicians guessing.
Physicians at the Children's Hospital Colorado in Aurora found that five of the 11 children experiencing paralysis who became patients at the hospital had enterovirus in their noses or throats but not in their spinal fluid, so researchers couldn't confirm it caused the paralysis.
Additionally, no trace of the polio virus was found in any of the children's spinal fluid although it is possible the virus was looked for too late and had already disappeared, according to the report.
Some of the symptoms children experienced include a fever roughly one week after the paralysis developed and meningitis-like symptoms, such as stiff necks and sensitivity to light.
The forms of paralysis have also varied greatly; some children experienced paralysis on only one side of their body, some said they had weakness in their limbs and others felt weakness in the muscles needed to talk and breathe. In addition to weakness, some of the children reported double vision or severe pain in their limbs.
According to the CDC, all of the paralyzed children experienced damage to their spinal nerve cells control movement merely hours before the paralysis set in.
Although there is no approved medication for enteroviruses and no vaccine, one child has fully recovered so far, according to the report.
More articles on viruses:
Canadian woman diagnosed with bird flu first in North America this year
Measles outbreak update: Reported cases top 70
Ebola virus genetics mutate, making drugs ineffective