DALLAS — The transmission of the Ebola virus to a nurse here forced the Centers for Disease Control and Prevention on Monday to reconsider its approach to containing the disease, with state and federal officials re-examining whether equipment and procedures were adequate or too loosely followed, and whether more decontamination steps are necessary when health workers leave isolation units. “We have to rethink the way we address Ebola infection control, because even a single infection is unacceptable,” Dr. Thomas R. Frieden, director of the C.D.C., told reporters.