Science closing in on polio-like virus that paralyzed children
http://www.sfchronicle.com/health/article/Science-closing-in-on-polio-like-virus-that-10961180.php
Scientists are closer than ever to proving that new strains of an old virus are to blame for recent waves of polio-like paralysis in children that have stumped doctors and alarmed parents across the country.
Laboratory mice exposed to the virus, called Enterovirus D68, often developed sudden-onset paralysis in one or more limbs a few days later, according to research published last week by a team of scientists from UCSF, the University of Colorado School of Medicine and the California Department of Public Health.
Studies in mice don’t always translate well to humans. But infectious-disease experts said the new research is probably the best proof they can obtain that the enterovirus was responsible for the polio-like illness that hit more than 200 children in the U.S. — including several in the Bay Area — in 2014 and again last year.
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Infectious disease experts said they hope the new research will encourage other scientists to home in on Enterovirus D68 and how it affects the human body, and ultimately develop a vaccine or drugs to treat it and prevent paralysis.
“This paper is a watershed event. It’s the step that needed to happen to move into the really critical steps of developing treatments for this really bad disease,” said Dr. Keith Van Haren, a Stanford neurologist who treated some of the first Bay Area paralysis patients and was not involved in the new research.
The paralysis outbreak emerged in early 2014, when California public health officials said at least 20 children in the state had been afflicted with a “polio-like illness.” The children typically lost movement in one or more limbs, often after suffering what had seemed like a bad cold, and the damage tended to be permanent.
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Then a wave of severe respiratory infections definitively linked to Enterovirus D68 swept over much of the United States, ultimately affecting more than 1,000 children — and intensifying interest in the virus.
Chiu and other scientists soon learned that the virus had mutated, undergoing small but important changes in its genetic code since it was first identified in the 1960s. Those mutations may have made it suddenly more dangerous, with the potential to cause severe respiratory illness and, occasionally, paralysis.
Still, scientists couldn’t link Enterovirus D68 directly to paralysis in children. In the 2014 outbreak, doctors were able to find the virus in spinal fluid — a strong indicator that it had infected the nervous system — in only one patient. The only places they could consistently find it was in the blood or respiratory secretions, and in half of patients they were never able to detect the virus.
What scientists needed was proof that the mutated virus could cause paralysis. The mouse findings appear to do just that.
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“A lot of people were dubious about Enterovirus D68 because they said, ‘Gosh, this virus isn’t known to be neurotropic and we’re not finding it in the spinal fluid,’” said Dr. Kenneth Tyler, a University of Colorado neurologist and the senior author of the paper. “We asked, ‘Would these (strains) produce a neurologic disease in mice, and would it be similar to what we saw in humans?’ And the answer was a resounding yes.”
The next step for scientists will be learning more about how Enterovirus D68 works and seeking ways to treat or prevent it. Encouragingly, the scientists found that healthy mice that were given antibodies from infected animals appeared to be protected, which bodes well for the prospect of a vaccine.
Infectious disease experts said they hope the new research will also encourage public health authorities to boost surveillance of Enterovirus D68, which can be difficult to detect. Most labs aren’t equipped to test for the virus.
