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http://www.sfgate.com/bayarea/article/Paralysis-cluster-cases-linked-to-polio-like-virus-6169033.php
Paralysis cluster cases linked to polio-like virus
By Erin Allday
Updated 10:16 pm, Monday, March 30, 2015
A team of researchers led by UCSF scientists has found strong evidence that recent, alarming clusters of sudden-onset paralysis cases — most of them in California and Colorado — were caused by the same virus that was also responsible for hundreds of severe respiratory infections in U.S. children last year.
Particularly worrisome is that the enterovirus identified in the research is a new strain that appears to have mutated to become more polio-like, raising the prospects of future outbreaks of the disease, scientists said in a paper published Monday.
“The changes were always in the direction to make it more similar to polio,” said Dr. Charles Chiu, head of the viral diagnostics laboratory at UCSF and lead author of the paper. “I want to make sure we don’t alarm people. There’s a chance this virus may never come back, which would be the best-case scenario. But we certainly need to be prepared.”
The virus scientists like Chiu have been hunting is called Enterovirus D68, which is a relatively common pathogen that typically causes mild symptoms associated with the common cold but can cause more serious illness.
Two years ago, however, doctors in California — including physicians at UCSF and Stanford — investigating a handful of cases of sudden-onset paralysis in children, noted that two patients carried Enterovirus D68.
The clusters
Then, last year, a massive wave of severe respiratory infections caused by Enterovirus D68 swept across the United States, targeting children. By the end of the year, more than 1,150 cases, all of them positive for Enterovirus D68, had been reported.
And at the same time, two hospitals — one in Colorado and one in California — reported small clusters of sudden-onset paralysis, with some of the patients testing positive for the same virus. Among the children eventually with paralysis, many have shown some improvement in symptoms but none has recovered fully.
But no one could say for sure that Enterovirus 68 was causing the paralysis. Baffling scientists and frustrating doctors, some of the affected children tested positive for the infection, but many did not.
Chiu’s team collected blood, tissue and fluid samples from 25 patients who were part of the paralysis clusters and used highly sensitive equipment to search for any traces of enterovirus. Most of those patients had never tested positive for enterovirus, but Chiu was able to detect Enterovirus D68 in 12 of them.
A full genomic analysis of the viruses Chiu found showed that almost all of them were of a mutated strain known as B1, which was only identified about five years ago. The strain has similar features to both the virus that causes polio and another virus — Enterovirus D70 — that’s also known to cause neurological problems.
“It’s a small study, and we’re not showing causality yet, but we’re really inching that way,” said Dr. Emmanuelle Waubant, a UCSF neurologist who treated some of the first California patients with sudden-onset paralysis but was not part of Chiu’s research team. “This work is definitely going to encourage investigators to go back to the bench and try to really understand better the neurological complication potential of this virus.”
Chiu and other scientists said they don’t yet have the “smoking gun” evidence they need to say for certain that Enterovirus D68 is the culprit in the paralysis cases. He wasn’t able to find any virus in the cerebral spinal fluid of affected patients, which would be a logical place for the pathogen if it’s causing neurological problems.
But viruses that cause paralysis — including polio-causing viruses — are notoriously tricky to locate, scientists say. And the fact that Chiu and other scientists haven’t been able to find any other possible causes of illness is another point in favor of Enterovirus D68.
It’s rare for Enterovirus D68 to cause paralysis and unclear why some patients end up with more severe symptoms than others. In the paper, scientists found the virus in a pair of siblings, one of whom suffered some paralysis and the other only minor cold symptoms. Individual genetics or environmental factors may explain the differences, and Chiu has plans to further study the siblings.
Just how concerning this virus is remains to be seen, doctors said.
Last year’s outbreak — including the hundreds of respiratory infections and the clusters of paralysis — are “not apocalyptic by any means,” said Dr. Keith Van Haren, a pediatric neurologist at Stanford’s Lucile Packard Children's Hospital who studied the first cases and was an author of the new paper. “But it’s potentially a serious, sentinel event of things that may come.”
One big question is whether Enterovirus D68 will make a comeback this year, Chiu said. Enteroviruses are not like influenza, which tends to reliably turn up every year with only two or three circulating strains. There are more than 100 strains of enterovirus, and many of them only show up sporadically, causing large clusters of illness before disappearing for many years.
“It’s hard to predict what will happen this year or next year. Certainly enterorvirus will crop up again,” Chiu said. “The question is will it be this strain or another strain? This year will be very informative.”
Outlook unclear
Meanwhile, the families affected by the paralysis still struggle with a lack of information about what caused the initial illness and what the long-term prospects are for the children.
Nirupa Muruhathasan, whose son Vikash, 11, lost partial use of his arm after falling sick two years ago, said while she’s eager to better understand what happened to him, she’s more interested in his future.
“He still does physical therapy every single day. He hasn’t plateaued yet. That’s the message I want to give other parents,” said Muruhathasan, who moved from the Bay Area to San Diego with her family last year. “I just feel like everybody wants to focus on the problem rather than finding a solution for these kids.”
