ROBERT SIEGEL, HOST:
While Ebola is grabbing headlines, another virus far less deadly is spreading among Americans. The Centers for Disease Control and Prevention has about 700 people, mostly children - have been hospitalized with an infection caused by Enterovirus D68. The virus usually causes respiratory symptoms, but recently, about a dozen people with Enterovirus D68 have developed paralysis. And five have died according to the CDC. NPR's Patti Neighmond reports on what we know and what we don't know about this virus.
PATTI NEIGHMOND, BYLINE: Enterovirus D68 infects thousands of Americans every year. It's part of a very large family of enterovirus strains - literally hundreds of them.
WILLIAM SCHAFFNER: They're called enteroviruses because they like the enteric system - that is the gastrointestinal system.
NEIGHMOND: In the gut, they cause stomach and bowel upset. But D68 has migrated says Dr. William Schaffner, an infectious disease specialist at Vanderbilt Medical Center in Nashville. And now it's targeting the throat and lungs.
SCHAFFNER: It likes the pharynx more than it likes the intestinal tract. And we know that respiratory viruses are spread very readily. Look at flu.
NEIGHMOND: And that could be one reason for the upsurge. The virus spreads more easily when it resides in the lungs then when it lives in the gut. It's transmitted in tiny, contaminated droplets when people cough, sneeze, or just closely mingle. Then there's timing. The season for Enterovirus D68 is late summer, early fall when school starts. And children who aren't prone to practice the best hygiene are in enclosed, crowded areas making things ripe for transmission. The virus isn't new. Schaffner says it's been around for decades, but this year something unusual happened.
SCHAFFNER: We've been tracking the varieties of enteroviruses throughout the country for three, four decades now. And this D68 virus has remained in the background. It's been rarely detected. Why should it suddenly rise up and become this year's hit-parade virus? We have no idea.
NEIGHMOND: Children who get hospitalized usually have wheezing and difficulty breathing. Most have asthma or other respiratory problems making them more vulnerable. But the five deaths are mysteries. Researchers say it's not clear what role, if any, the virus played in the deaths. In Rhode Island, an 11-year-old girl who died was also infected with a severe bacterial staph infection. And a few states have hospitalized children suffering from muscle weakness in their arms and legs raising concerns about a polio-like virus.
SCHAFFNER: And of course, all of these children have been vaccinated against polio. This is not polio. But it could be paralysis caused by another enterovirus - against which we don't have vaccines.
NEIGHMOND: Federal health investigators are working to figure out just what's going on. Why have cases of this virus suddenly spiked, and why does it seem more potent? Right now, there are more questions than answers. Mark Pallansch with the Centers for Disease Control and Prevention.
MARK PALLANSCH: Anytime we see change in the epidemiology of these viruses, we seek to understand why some viruses are common every year - other viruses can spike in specific years and then not be seen for very long periods of time - even up to decades.
NEIGHMOND: The CDC is tracking hospitalizations nationwide and asking states to provide medical histories and specimen samples from patients suspected of Enterovirus D68 infection. Pallansch cautions that severe symptoms, especially the few cases of paralysis, are extremely rare. The vast majority of children who get infected with the virus will have only mild symptoms and get better quickly. Patti Neighmond, NPR News. Transcript provided by NPR, Copyright NPR.