How a viral siege is making some people sick for weeks, even months

It started in mid-September with Vance, 5, who came down with RSV and wheezed so badly that his skin was pulling in and out of his ribs with every breath. His little brother Banks, then 11 months old, caught it too. Things were just starting to get better in October, when the boys caught a nasty cold that resulted in more sleepless nights. In November, the flu hit, bringing fevers of 102 degrees.

“It feels like a never-ending cycle,” said their mom, Michelle Huber of Louisville. “We are beyond exhausted.”...