Virus under microscope
Cold-like bug may be linked to paralysis in children
Amid the barrage of chilling news about Ebola and its toll, another virus attracted relatively little attention recently as it coughed and sneezed its way into Canadian lives.
Enterovirus D68, however, is finally getting its moment in the spotlight. Being likened to polio will do that.
Public health officials had warned doctors earlier this fall to be on the lookout for EV-D68, a cold-like bug that was showing up in unusual numbers and causing serious respiratory complications for a small minority of young patients, some of whom have wound up on breathing machines.
Then in the past few days, hospitals began reporting an even more alarming symptom. A number of patients, some but not all of whom have actually tested positive for the virus, were experiencing poliolike paralysis or weakness in one of their limbs.
Hospitals in Toronto and Hamilton, Ont., Edmonton, Calgary and Vancouver have all reported such cases in the past two to three days.
If the enterovirus is to blame for those symptoms, it would mark an unexpected and worrying development for a bug that has proven generally insignificant since it was discovered five decades ago, said Edmonton’s Joan Robinson, chairwoman of the Canadian Pediatric Society’s infectious disease committee.
“It seems pretty clear that this virus has changed in some way, and is now causing brand-new clinical manifestations,” said Dr. Robinson. “I think it’s difficult not to be concerned about a virus that can cause a polio-like illness.”
Single-limb weakness in polio patients would sometimes spread to respiratory muscles, Dr. Robinson noted, making it difficult to breathe and landing many patients in so-called iron lungs that did the work for them.
As frightening as reports of partial paralysis sound, it is still unclear whether EV- D68 represents a serious new viral threat, or just another part of the wave of seasonal pathogens that affects most people mildly, and an unlucky few severely.
Only some of the paralysis cases have tested positive for the enterovirus, and even when they do, that does not necessarily mean EV-D68 is the cause.
Several other bugs — from West Nile to campylobacter to flu — can trigger similar symptoms, noted Dr. Dr. Bryna Warshawsky of Public Health Ontario.
Indeed, a little-known federal disease-surveillance program — set up to ensure the country remains free of polio — has documented between 24 and 64 cases annually of “acute flaccid paralysis” in children under 15 for the past 18 years.
Enteroviruses are a group that includes about 100 different “serotypes,” including the rhinoviruses that cause the common cold, and polio. It once sickened thousands of Canadians a year, leaving many paralyzed or dead, but was declared officially eradicated here in 1994, beaten back by two of the most famous vaccines ever developed.
Enterovirus D68, discovered in 1962, causes mild, cold-like symptoms in most people infected.
There have been sporadic outbreaks over the years, but most disease labs do not typically screen for it, so it may be more prevalent than test results suggest, said Dr. Robinson.
Its somewhat innocuous reputation changed this year, as it began showing up in much greater numbers than usual, with a small proportion of children experiencing wheezing and serious breathing problems. Many of those have been patients who have asthma.
“We know that children are a bit more at risk [for infection] and probably for respiratory problems, because they haven’t been exposed to this virus before,” said Dr. Warshawsky.
The law does not require reporting of EV-D68, but it appears there have been doz- ens of cases confirmed nationally.
British Columbia has identified four patients with the virus suffering from limb paralysis or weakness, while Alberta is investigating cases in Edmonton and Calgary, said Dr. Robinson. Another four patients — one of whom has tested positive for EVD68 — are being investigated at a hospital in Hamilton, while Sick Kids in Toronto is testing three children with muscle weakness for the infection.
“It’s very uncommon to see this type of neurological presentation happening in children,” Dr. Brandon Meaney, head of pediatric neurology at McMaster Children’s Hospital, told the Hamilton Spectator.
“Every region across Canada and the United States is reporting a small but significant cluster.”
And yet, such symptoms are by no means unheard of in this country. The Public Health Agency’s surveillance system recorded 24 cases of acute flaccid paralysis in children under 15 last year. The numbers have fluctuated to as high as 64.
None has been triggered by polio. Most are a result of Guillaine-Barré syndrome, where the body’s immune system attacks the nervous system, causing partial or total paralysis, usually temporary, the agency says.
While the cause is an open question, Guillaine-Barré appears linked to infection with certain viruses and bacteria, including the flu.