Most of the AFM cases that the CDC has studied have no indication of any particular infection. The average age of those affected is four years old and more than 90 percent of cases overall are in children under 18, Dr Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases at the CDC, told reporters in a media call on Thursday.
"At this moment, we don't know if it's a virus that is coming and producing direct damage of the gray matter in the spinal cord, or if a virus is triggering immunological responses that produce a secondary damage in the spinal cord", Carlos Pardo-Villamizar, a neurological disease expert at the Johns Hopkins University School of Medicine who recently authored a paper on AFM, told Kaiser Health News. They've been seeing an increase in cases since 2014.
The CDC received information on 33 confirmed cases of AFM in 2017, 149 cases in 2016, 22 cases in 2015, and 120 cases in the latter part of 2014.
"We have [had] two patients we have treated in CHEO for [acute flaccid paralysis] since the summer", said Dr. Sunita Venkateswaran, a pediatric neurogologist with the children's hospital.
Acute flaccid paralysis, also known as acute flaccid myelitis, is experiencing a small surge in the USA, where more than 60 cases have been confirmed in recent weeks. "That is why we say that this disease is incredibly rare", Messonnier said.
HuffPost Canada has reached out to the Canadian Paediatric Society for comment.
"While we don't know the cause of most of the AFM cases, it's always important to practice disease prevention steps, such as staying up-to-date on vaccines, washing your hands, and protecting yourself from mosquito bites", the CDC said. But there are many enteroviruses, and they usually cause symptoms similar to the common cold, as do rhinoviruses, adenoviruses and many other viruses.
"What makes it worse is not knowing what caused it", said Erica Palacios, whose 2-year-old daughter, Abigail, began showing signs of AFM last month.
It is also unclear who could be at higher risk of developing AFM, Messonnier said.
"We don't know a lot about the long-term prognosis of AFM right now".
Christenson understands why parents are concerned and he says prevention is key. While potential causes may include certain viruses, environmental toxins and genetic disorders, the CDC says, "AFM can be hard to diagnose because it shares numerous same symptoms as other neurologic diseases". These kids have a sudden onset of weakness.