A small number of children in California have contracted a polio-like illness since 2012, and doctors and public health officials don't yet know why.
Dr. Keith Van Haren, a pediatric neurologist at Stanford University's Lucile Packard Children's Hospital, told the Los Angeles Times that the illness is not polio, noting that all of the patients he studied had been vaccinated against the disease. However, Van Haren noted that in five cases he had studied, all of the children developed paralysis in one or more of their arms or legs, and none had recovered limb functions after being diagnosed.
The first case was reported in the fall of 2012, when a doctor requested polio testing on a child who had developed a severe paralytic illness. California health officials did not release to the Times the total number of cases reported. Van Haren told the paper that he was aware of approximately 20 cases in total. The median age of the children diagnosed is 12 years old.
The symptoms sometimes occur after a mild respiratory illness. Carol Glaser, leader of a California Department of Public Health team investigating the cases, said a virus that is usually associated with respiratory illness but which has also been linked to polio-like illnesses was detected in two of the patients. Other cases were reported in children who suffered symptoms that could not be linked to known causes like West Nile virus or botulism.
Glaser also told the Times that scans of the patients' spinal cords revealed damage patterns similar to those found in polio sufferers. Two children tested positive for enterovirus-68, which is usually associated with respiratory illness, but has been linked to polio-like illnesses as well.
Glaser encourages local physicians and health officials who are aware of similar symptoms in children to report the cases to her team.
The Associated Press contributed to this report.