The unusually high number of hospitalizations reported now could be "just the tip of the iceberg in terms of severe cases," said Mark Pallansch, a virologist and director of the Centers for Disease Control and Prevention's Division of Viral Diseases.
"We're in the middle of looking into this," he told CNN on Sunday. "We don't have all the answers yet."
Ten states have contacted the CDC for assistance in investigating clusters of enterovirus -- Colorado, North Carolina, Georgia, Ohio, Iowa, Illinois, Missouri, Kansas, Oklahoma, and Kentucky.
Enteroviruses, which bring on symptoms like a very intense cold, aren't unusual. They're actually common. When you have a bad summer cold, often what you have is an enterovirus, he said. The season often hits its peak in September. READ MORE