Six-year-old Naiya Clarke was recovering from what seemed like a cold when she told her mother her right arm felt “funny.” Within two days, the Edmonton girl was in hospital, breathing through a respirator and paralyzed in every part of her body except her fingers and toes.
“It was my worst nightmare," her mother, Iesher Clarke, says of that period two years ago, describing her powerlessness to help. "I’ve protected her from everything in life.”
Naiya Clarke, 8, has recovered some use of her right arm after a 2016 bout enterovirus-D68, which caused a form of paralysis called acute flaccid myelitis.Amber Bracken/The Globe and Mail
Hospitals in Toronto and Montreal are reporting an uptick in cases such as Naiya’s: an extremely rare syndrome, or set of symptoms, called acute flaccid myelitis (AFM), that mostly affects children and involves a sudden weakness of one or more limbs, resembling polio. Montreal Children’s hospital has had three cases in the past three weeks. Toronto’s Sick Kids Hospital, which typically sees one or two a year, has confirmed about a dozen.
The symptoms can include sudden weakness and a loss of reflexes in one or more limbs, facial drooping, slurred speech, difficulty moving the eyes and pain.
The Public Health Agency of Canada tracks cases of acute flaccid paralysis, of which AFM is one type. Canada averages about 45 a year, according to Public Health Agency data, and has so far this year confirmed 21 cases. Fifteen more are under investigation.
Cases in the United States are soaring: 191 are under investigation this year and 75 have been confirmed, up from 33 confirmed last year, according to the Centers for Disease Control and Prevention.
AFM can be caused by different factors, from environmental toxins to autoimmune disease to infections such as the West Nile virus. However, doctors and researchers do not yet know what is behind the latest wave of cases, but some believe it may be the return of a virus whose presence has preceded similar spikes in the past.
Some researchers suspect certain children may be more susceptible than others to AFM if they are “immunologically naive” – that is, they have not developed immunity against a given pathogen that causes the condition – or if their immune system produces an exaggerated response that damages the spinal cord. Naiya, for example, was always prone to allergies and asthma attacks, which are immune-system responses. Her brother, then 11, who was not prone to allergies or asthma, had the cold-like symptoms at the same time as Naiya, but recovered fully and never developed AFM.
If past surges are any indication, the strongest hypothesis suggests the culprit in the latest clusters may be one or more of a group of viruses called enteroviruses.
For Jeffrey Pernica, head of the division of infectious disease at McMaster University’s department of pediatrics, the latest wave of AFM looks familiar. A similar cluster occurred in the fall of 2014, with 25 patients in Canada, which coincided with a rise in cases of an enterovirus called D68. For most, this virus leads to little more than coughing and wheezing, and perhaps a mild fever. But, he says, because the widespread circulation of the virus immediately preceded cases of AFM, it likely played a role. He adds experiments have also have shown enterovirus D68 can produce AFM in lab animals.
He saw six cases of AFM at his hospital in Hamilton at that time, although none this year.
At Montreal Children’s Hospital, Christos Karatzios, a pediatric infectious disease specialist, adds there are additional reasons to believe an enterovirus is to blame. For instance, the latest cluster of AFM cases corresponds with the timing of enterovirus infections, which typically occur in late summer and fall, he says.
In the United States, Charles Chiu, a professor in the department of laboratory medicine at the University of California, San Francisco, has been studying the link between AFM and enteroviruses since 2012. He says enteroviruses, including D68 and A71, have been found in nasal and oral swabs of some children with AFM, but it is difficult tell whether they are the cause of the paralyzing syndrome.
One reason is that these viruses have not been detected in the spinal fluid of children with AFM, he says.
Without that key evidence, he says, “we don’t have a smoking gun.”
In Edmonton, Naiya was treated with intravenous immunoglobulin and steroids, as well as plasmapheresis – a process of filtering blood that is used for some autoimmune diseases. Ms. Clarke says Naiya’s stool and blood samples showed enterovirus D68, but doctors were unable to explain her sudden paralysis.
Naiya, now 8, has regained mobility and feeling in almost all of her body. After nerve transplant surgery last year, she can partly use her right arm. She still cannot walk long distances, but Ms. Clarke says she continues to improve. Not all children regain mobility.
Naiya plays with the family dog, Trauma, at home in Edmonton on Monday.Amber Bracken/The Globe and Mail
Dr. Karatzios says parents should take their children to the emergency department immediately if they show any sudden weakness in their limbs.
He said if an enterovirus really is the cause of AFM, the number of new cases is expected to dwindle soon as enterovirus season ends.
Wency Leung