Transcript for Little Boy's Fight to Walk Again After Contracting Enterovirus
Tonight, the CDC has declared a flu epidemic, but as hospitals scramble to contain the outbreak, there's another disease putting children at risk, and it's deadly. Doctors now taking emergency measures to control the Terri terrifying enterovirus. "Nightline" anchor juju Chang joins a brave 4-year-old who is fighting it with everything he's got. Reporter: This year's flu season already an epidemic. Alarming public health officials and perhaps shaping up to be deadlier than in years past. Every year, you have to be concerned about the flu. Some people say, it's just the flu, but people die from the flu. 15 children have already died this year from the flu. Reporter: This year's flu vaccine, a mismatch, according to officials, leaving near little everyone vulnerable to this season's strain. 22 states reporting a surge of E.R. Viments for flu symptoms. Flu season is a really difficult time in a hospital. In the emergency room. You can get flooded with patients who come in, some may just have the common cold. Some are going to have the flu. Reporter: This is the second round of problems for hospitals. Just months ago, our cameras on the front lines at the university of Michigan, as they battle against another respiratory illness that targeted the most fragile. Children. It's called enterovirus. How you doing? Breathing feeling any better? Let me take a listen. Take some deep breaths for me. Reporter: Dr. Marie mozan saw a nasty strain of the enterovirus sweeping the country that in extreme cases caused death. We added extra doctors and nurses every day on every shift. And we used or existing doctor staff, our faculty staff, said, guys, we have to run an enterovirus shift. Reporter: Before enterovirus struck, Alan was a typical 4-year-old. Goofy and playful earlier this year. But just after this night, Alan caught a common virus, a fever, a nagging cough. But unlike countless others who recover easily, Alan w0u7bd sound up in the hospital, paralyzed over 80% of his body. Unable to lift his head. He's able to stand up, because he cannot do that right now. Reporter: When we first metal land, his days were like this, on a feeding tube, because his throat muscles are still affected. Theparalysis, a nightmare for his mom. He was screaming, help me, mom. I'm bawling. I don't know what to do. Reporter: What's the hardest part been for you? Seeing him in pain and not being able to move. Reporter: The team here at cs children's hospital believe a virus which caused Alan's cough may also have caused his paralysis. It comes from the same virus family as polio. Across the country, families are dealing with the aftermath of paralysis. Clusters in California, Colorado, then rolling eastward. More recently, in Texas and fair vous southern states. Michigan was hard-hit. We now have seven patients that we've seen present with some type of paralysis, either upper or lower extremity. Reporter: Doctors coping with this outbreak as they're trying to crack the mystery of how it attacks. As soon as the respiratory settles down, we started seeing children come in with this acute paralysis and people started to link the enterovirus with that. Reporter: Dr. Marie Lozon saw a spike of enterovirus and paralysis. She started putting the pieces together. I cannot speak to call sags. I'm not saying the enterovirus brought about the paralysis, but you can see where the link came. Reporter: But as disturbing as the growing number of paralyzed children, enter rovirus was, in a handful of cases, proved deadly. There have been cases of children having enterovirus and dying. That is true. But we have more children die every year from inflew when Sae. Reporter: Dr. Lozon says the enterovirus is now over. While it is impossible to predict the intensity of next season, she says, make no mistake. It will return. Doctors are still learning from kalgss they are treating months later. How much longer do they think it will take? They haven't really told me that. Reporter: Twice a day, Alan gets physical therapy, where he's strapped to a gurney to retrain his muscles. His mom sails his feerms are as much out of frustration as pain. Okay? We're going to count to five. We're going to count to five and we'll be done. One, two, three, four, five. Reporter: It's tough for a 4-year-old to understand why he can no longer play with his little brother. But mild the frustration and pain, there's a glimmer of hope. How much progress have you seen so far? Well, he already is really able to move all of his extremities against gravity, so, that's super good news. And he has a lot of head control now. He's actually starting to be able to sit on his own. Reporter: And his dedicated medical team can't answer the ultimate question, will he walk again? Will he full little recover? Do you see him running around, you know, gaining that kind of strength again? It's difficult to predict, for sure. I definitely think we'll get him moving again. We'll probably get him moving on his feet. But if he's running the same also his peers is not as positive about. Reporter: Though there's little known about ways to prevent enterovirus, Dr. Lozon says, our best defense is common sense. How viral phonetic should we be right now? I think that a measure of common sense always makes sense. We have viral surges every year. And now enterovirus is just another of the viruses that we've seen. I think we cover our cough. We use good hand hygiene. You would never send your child to school feverish and coughing their brains out. If we do that, we're going to get through this. Reporter: Vigilance is key. But rather than panic, she says we should guard against the ones we can protect against. After months of treatment and therapy, just before Thanksgiving, a long awaited homecoming. Being home for the holidays may be the best medicine. Alan continues to show progress. A small miracle. Alan's recovered enough muscle tone, he's starting to walk again. A few small steps for Alan. One giant leap of determination. For "Nightline," I'm juju Chang in Ann Arbor, Michigan.
This transcript has been automatically generated and may not be 100% accurate.