Idaho has experienced its worst epidemic of whooping cough since at least the late 1950s, and health officials say the outbreak apparently will continue into 1989.

The number of 1988 cases is 357 and rising, but the end of the epidemic may be near, state immunization coordinator Bob Medlin said Tuesday.The number of cases peaked in the spring and has decreased since, Medlin said. If Idaho's outbreak is like others, the number of cases will return to normal - about 10 a year - by spring.