Mysterious cases of paralysis in U.S. children over the last year have researchers searching for the cause of the illness. Now, a new study suggests that a new strain of a poliolike virus may be responsible for some of the cases. So far, more than 100 children in 34 states have suddenly developed muscle weakness or paralysis in their arms or legs, a condition known as acute flaccid myelitis, according to the Centers for Disease Control and Prevention. Previously, researchers linked a virus called enterovirus D68 (EV-D68), which can cause respiratory illness similar to the common cold, with some of...