Health officials are looking for the cause of a neurologic illness that 's affected 10 children in Colorado . The children were hospitalized between August 9 and September 28 with muscle weakness in their limbs , according to the Centers for Disease Control and Prevention . Something is affecting the children 's motor nerves , causing weakness primarily in their shoulders , triceps , biceps and hips , says Dr. Joyce Oleszek , a pediatric rehabilitation specialist at Children 's Hospital Colorado . Doctors are also seeing some weakness in the neck and facial muscles in these patients . `` It seems to be attacking the spinal cord and brain stem , '' Oleszek said at a press conference Monday . MRI tests spotted abnormalities in the children 's spinal gray matter . Most of the children experienced a respiratory illness before being admitted to the hospital , although only two had a history of asthma . The latest case was a girl who arrived at Children 's Hospital Colorado over the weekend . She and three of the other patients are still at the hospital . The rest have been discharged , said Dr. Sam Dominguez , a microbial epidemiologist at the hospital . Doctors do not know if the neurological damage will be permanent . The CDC is investigating the cause of these symptoms . Health officials do not believe that the cases were caused by polio , as at least eight of the 10 children are up to date on their polio vaccinations . `` We do n't know , at this point , if there is any association between the enterovirus EV-D68 that 's circulating and the paralytic conditions some of the children in Colorado are experiencing , '' CDC spokesman Tom Skinner said . Tests of the children 's cerebrospinal fluid came back negative for enteroviruses and West Nile virus . But a test of their nasal passages found enterovirus in six out of eight patients who were tested . Of those six , four tested positive for enterovirus D68 , which has been sending children across North America to the hospital with severe respiratory illnesses . The other two test results are pending . `` It could be something else . That does n't prove cause and effect , but it 's circumstantial evidence , '' said Dr. Anthony Fauci , director of the National Institute of Allergy and Infectious Diseases . The cause `` still remains a puzzle . '' Enterovirus : My son was 'like a goldfish gasping for breath ' A cluster of children with similar paralysis symptoms was identified in California last year . Samples from two of the children tested positive for enterovirus D68 . Enterovirus D68 is part of the Picornaviridae family , which also includes the poliovirus , other enteroviruses and rhinoviruses . Enteroviruses are very common , especially in late summer and early fall . The CDC estimates that 10 million to 15 million infections occur in the United States each year . These viruses usually appear like the common cold ; symptoms include sneezing , a runny nose and a cough . Most people recover without any treatment . But some types of enterovirus are more serious . These can cause hand , foot and mouth disease ; viral meningitis ; encephalitis ( inflammation of the brain ) ; an infection of the heart ; and paralysis in some patients . This year , enterovirus D68 seems to be exacerbating breathing problems in children who have asthma . The virus has infected at least 277 people in 40 states , according to the CDC . Cases have also been reported in Canada . Children 's Hospital Colorado has treated over 4,000 children with severe respiratory illness since August 18 , said Dr. Chris Nyquist , medical director for Infection Prevention and Control . About 10 % were admitted . CNN affiliate WCBS reported Friday that a New Jersey toddler died last week from a severe respiratory illness and that the CDC will be testing samples to see whether he had enterovirus D68 . The CDC is asking other hospitals across the country to be on the lookout for similar cases and to send in information on any patients with these symptoms . `` Parents should n't panic , '' Nyquist says . `` This is very , very uncommon. `` Common-sense things , like frequent hand-washing and avoiding sick people , can help protect kids from becoming infected , she said .
`` It seems to be attacking the spinal cord and brain stem , '' doctor says . MRI tests spotted abnormalities in sick children 's spinal gray matter . Health officials are looking for the cause ; it may be enterovirus . Ten children in Colorado hospitalized with limb paralysis .