In 2010, five California residents have died from the disease. All were Latino babies under 3 months old who were too young to be immunized. Also, a sixth infant death is under investigation.
Typically, a case of whooping cough appears similar to a common cold up to approximately two weeks. This is followed by weeks or months of rapid coughing fits that sometimes end with a whooping sound.
Officials advise seniors and women in child-bearing years to get vaccinated.
AP contributed to this report.