Four months after enterovirus D68 sickened thousands of children in North America, even killing some, doctors are still scrambling to learn more about the virus and its risk to the public.

While most EV-D68 infections only cause cold-like symptoms, and few to no complications, scientists in Canada and the U.S. tracked a surge in cases last year. The virus sent thousands of children across North America to hospital with respiratory distress, and some of those cases were linked to weakness, paralysis and even death.

The virus hit B.C. first in September. According to Dr. Danuta Skowronski, an infectious diseases specialist at the B.C. Centre for Disease Control, up to two-thirds of the province’s 200 EV-D68 cases led to hospitalization during the outbreak.

Soon after, other Canadian provinces and regions across the U.S. were seeing children with severe breathing difficulties linked to the virus.

More mysterious cases developed, like Evan Mutrie, a healthy, 20-year-old football player from Kamloops, B.C., who contracted the disease and become paralyzed from the neck down. And children like 13-year-old Dan Dugan saw a cough and fever develop into paralysis of the legs.

"I could feel them (my legs) but they just wouldn't move," said Dugan.

More recently, a B.C. child became the third fatality in the province linked to the EV-D68 infection. The child, who was under the age of five, died in November but the B.C. Centre for Disease Control was only notified of the fatality last week.

While the outbreak appears to be over, scientists are still scrambling to figure out whether EV-D68 has morphed from a mild virus into a potentially crippling disease. At this point, the associated paralysis seems to be permanent in some cases.

"The children who have followed up seem to have persistent limb weakness," said Dr. James J. Sejvar, a neuroepidemiologist with the U.S. Centers for Disease Control and Prevention.

Skowronski said researchers are still in the "learning phase" with the virus.

“We found some important associations that could be significant to public health and we need to learn more about that,” she said.

While doctors stress that the vast majority of children only had mild symptoms and the number of cases appear to be on the decline, they are still searching for answers in case the virus makes a comeback in 2015.

With files from CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip