Instances of the bacterial disease have been on a steady rise in California for a few months now, with a total of 3,458 cases of it reported since Jan. 1, more than all the cases reported in 2013, said Dr. Ron Chapman, director of the California Department of Public Health.
Chapman said the best way to prevent the spread of the disease is to make sure children are immunized.
"Preventing severe disease and death in infants is our highest priority," he said. "We urge all pregnant women to get vaccinated. We also urge parents to vaccinate infants as soon as possible."
Cases of whooping cough, or pertussis, tend to peak every three to five years, the state health department said in a statement. During the last peak in California, in 2010, 9,159 cases were reported.
The Centers for Disease Control and Prevention recommend children get the pertussis vaccine at 2 months, 4 months, 6 months 15 to 18 months, and 4 to 6 years.
Whooping cough usually starts with cold-like symptoms, including a mild cough and fever, the CDC says.
Severe coughing and coughing fits can continue for weeks after that, resulting in a loud whooping sound as the infected gasp for air.
In babies under 1 year of age, there may be a dangerous change in breathing pattern.