Recent cases of inexplicable paralysis in a few children in British Columbia and the United States may have no connection to the seasonal enterovirus D68, health officials say. Some of the children tested negative for the respiratory infection that is sweeping across the United States, while all show damage to the tissues at the centre of the spinal cord.
In the past eight weeks, a growing number of cases of partial paralysis in children have been identified in the United States, including 10 in Colorado, three in Missouri, and as of Tuesday, four cases in Massachusetts. Since late August, two young people in British Columbia infected with the seasonal illness enterovirus D68 (EV-D68) have suffered limb weakness, partial paralysis and respiratory symptoms.
Mark Pallansch, director of the division of viral diseases at the U.S. Centers for Disease Control and Prevention, said he could not comment on cases outside Colorado, but he emphasized that scientists are exploring all avenues to pinpoint the cause of the children's neurological symptoms.
He noted that scientists have isolated three different respiratory viruses, including EV-D68, in the Colorado patients. But the infections are not consistent among the patients, "and some have no detectable [infectious] agent," Dr. Pallansch said. As of yet, "we don't have a specific cause of the cases that is consistent with all of the available data," he said.
The Colorado patients' spinal fluids have tested negative for polio, adenoviruses (a frequent cause of respiratory illness and diarrhea in children) as well as West Nile virus, Dr. Pallansch said. Researchers are also looking at potential causes for paralysis that are not infectious, he added.
Both B.C. patients who developed paralysis had spinal lesions and tested positive for EV-D68, a viral infection that has been associated with an increase in mild to severe respiratory illnesses this fall. The United States is experiencing a nationwide outbreak. In Canada, clusters of mild to severe respiratory illness caused by EV-D68 have appeared in Alberta and Windsor, Ont., since the beginning of the school year. The Public Health Agency of Canada said it could not confirm whether there are cases of paralysis in addition to EV-D68 outside B.C., since provinces are not required to notify the federal agency of new cases.
Health officials in British Columbia caution that more cases of respiratory illness due to EV-D68 may emerge in that province since children returned to school on Sept. 22 after a teacher's strike. "There may be an upswing in cases," said Danuta Skowronski, lead epidemiologist on emerging respiratory viruses at the B.C. Centre for Disease Control. She noted that the majority of unexplained cases of paralysis have been in preschool children, but added that one of the B.C. patients with neurological symptoms is between 15 and 20 years old.
In late August, the young adult awoke with weakness in the right arm after a day of flu-like symptoms including mild fever, general aches and fatigue. Within 24 hours, the patient had breathing difficulties. More than month later, the patient is still on a breathing machine.
The other B.C. patient, aged between 5 and 10 years, developed headache, neck pain and paralysis in the left arm several days after the onset of cold-like symptoms including fever, cough, runny nose and congestion. Nearly a month later, the child has shown no neurological improvements. Although it is uncertain whether EV-D68 causes neurological symptoms, Dr. Skowronski advised the public to take precautions because there is no vaccine or anti-viral treatment for EV-D68.
The best defence is a return to classic public health measures, such as frequent hand washing with soap and water, "especially before and after touching the face," she said.