The pertussis (whooping cough) epidemic that started last spring has continued unabated through fall. The California Department of Public Health said in its Nov. 26 report that nearly 10,000 cases have been reported this year.

The majority of cases have occurred in infants and the one fatality was of an infant 5 weeks old at the time of the disease onset.

The last pertussis epidemic in California was in 2010 when about 9,160 cases were reported. For several years, since the 1990s, the overall incidence of pertussis has increased in California. One reason for the increase, according to CDPH officials, is the use of acellular pertussis vaccines, which cause fewer reactions than the whole-cell vaccines that preceded them, but do not protect as long.

The appearance of whooping cough is occurring throughout the state. About 350 individuals have required hospital stays and nearly a quarter of these people needed intensive care.

Los Angeles and San Diego counties have seen the greatest number of cases, while Sonoma, Napa and Marin counties have the largest ratio of cases per 100,000 residents. Riverside County has reported 405 cases of pertussis, about a quarter of San Diego County cases. This represents about 18 cases per 100,000 persons compared to Sonoma’s ratio of 141.

Besides the persistence of pertussis, influenza season has started. CDPH reports, “Influenza activity in California is low but increasing.” Current hospital visits are considered within expected levels for this portion of the flu season.