The number of reported whooping cough cases climbed to 2,174 last week, six times the total at this time last year in an epidemic expected to be the worst in 50 years, public health officials said.

Dr. Mark Horton, director of the California Department of Public Health, urged residents to get vaccinated against the highly contagious upper respiratory disease, also known as pertussis. (Read more: "Facts about whooping cough.")

“The pertussis epidemic is a sobering and tragic reminder that diseases long thought controlled can return with a vengeance,” Horton said in a statement Monday. “We can protect ourselves and the most vulnerable in our community by getting vaccinated today.”

Last week, officials announced that a San Diego County baby had died of whooping cough. It was the seventh pertussis death statewide. All those killed by the infection have been infants, including three babies in Los Angeles County.