TORONTO -- A new threat is emerging in the outbreak of the respiratory illness enterovirus D68 -- a small number of infected patients in Canada and the U.S. have developed polio-like symptoms.
Health officials in British Columbia say two young males hospitalized with the respiratory virus have developed paralytic symptoms: a child between five and 10 years old is experiencing weakness in one arm that has not improved for nearly a month, while a teen aged 15 to 20 also developed weakness in one arm and is still on a breathing machine after being hospitalized for about the same period.
The two young patients, whose paralysis set in about the same time as other symptoms began, live several hundred kilometres apart and have no connection to one another, B.C. officials said.
Also Wednesday, Alberta reported that doctors are investigating whether four children with respiratory illness coupled with paralytic symptoms, or "neurological syndrome," are infected with enterovirus D68, a spokesman for Alberta Health Services said from Calgary.
Doctors in the U.S., which reported its first death Wednesday related to the outbreak, are also seeing sporadic cases of paralysis complications among patients. Late last week, the Centers for Disease Control alerted practitioners to be on the lookout for polio-like symptoms in children diagnosed with enterovirus D68, which is also known as EV-D68.
Dr. Danuta Skowronski, an infectious diseases specialist at the BC Centre for Disease Control, put out an alert late Tuesday about the two B.C. cases on ProMED, an online infectious diseases newsletter commonly used by doctors and researchers to inform that community about disease developments.
But the potentially nasty turn taken by EV-D68 did not come as a complete surprise to Skowronski.
"You know with any infectious disease, there is a spectrum of illness," she said Wednesday from Vancouver. "Most enterovirus infections are mild or even asymptomatic, but with other infectious diseases we do see a spectrum of illness and we should expect that also with D68, with a small proportion (of patients) showing severe complications."
Skowronski said doctors are still learning about EV-D68, which was first identified in 1962 and has since caused a number of outbreaks around the world.
There are more than 100 enteroviruses, the second most common cause of the common cold after rhinoviruses.
Polio, which can be prevented with vaccination, is also an enterovirus, but from a different family than EV-D68, which is closer in genetic structure and function to rhinoviruses -- it doesn't replicate in the acidic environment of the gastrointestinal tract and prefers temperatures around 33 C, unlike other enteroviruses.
EV-D68 usually starts with a runny nose, sneezing and coughing, and most children develop only mild to moderate symptoms that typically resolve on their own. However, in some cases, the lower airways become compromised, leading to wheezing and difficulty breathing that requires urgent medical attention. Children with asthma or other underlying respiratory conditions are the most commonly affected.
Since the late-summer outbreak began, there have been dozens of confirmed cases in western and central Canada, including 50 in Alberta alone. In the U.S., where cases began showing up before coming into Canada, the CDC says EV-D68 has been confirmed in 472 people in 41 states and the District of Columbia.
Meanwhile Wednesday, the U.S. announced its first EV-D68-related death. A 10-year-old Rhode Island girl died last week of a staph infection associated with the virus, which that state's health department called "a very rare combination."
B.C. has confirmed eight cases of the virus, including the two boys with weakened arms, but Skowronski said she can't comment on the latter patients' prognosis. In previous cases of enterovirus-related paralysis, there has been full recovery in some patients, partial recovery in others.
"It's impossible to speculate or predict what may happen. It really is a question of how things evolve over the next several months."
There is much about the EV-D68 strain that is unknown, including its exact genetic makeup and whether it carries any particular virulence factors that could contribute to polio-like symptoms.
Skowronski said doctors and researchers need to pool case information and share genetic sequences of the virus taken from a variety of patients across North America to see if there are patterns pointing to a link with more severe disease, including polio-like symptoms.
"There's likely a combination of individual and virus factors, but while we have the viruses we really need to investigate those to see what may be the secrets within the genome of the virus that will partially, if not fully, explain the severe complications that it's causing."
Polio has been eliminated in most of the world because of widespread vaccination, although the disease remains endemic in Pakistan, Nigeria and Afghanistan, and a vaccine may need to be developed for polio's cousins, said Skowronski, adding that doctors would first need to determine the exact impact and burden of disease caused by the bugs on the population.
"So it may be that we need to be working further on the developing of a vaccine candidate for other enteroviruses, and notably D68, which seems to be causing some severe manifestations in some patients."
