California health officials announced Friday that whooping cough (also known as pertussis) has reached epidemic levels in the state. The Department of Public Health reported 809 new cases of the infection, bringing the 2014 total to 3,458. That's 1,000 more cases than all of last year.
Four Bay Area communities have been hit particularly hard: Sonoma, Napa and Marin counties and Berkeley, which reports separately from the rest of Alameda County.
The overall state incidence rate is about 9 cases per 100,000 people, the CDPH says. But for Sonoma County the rate is 103 per 100,000; in Napa it's 65, and in Marin it's 53. Berkeley's rate is lower — 25 per 100,000; but that's three times higher than the rate for Alameda County as a whole. The rest of the Bay Area reports rates between a low of 6 per 100,000 in Santa Clara County and 17 per 100,000 in Solano County.
The CDPH said this year's epidemic is due at least in part to the cyclical nature of pertussis, which officials say peaks every three to five years. The last peak was in 2010, when the state had more than 9,000 cases and recorded 10 infant deaths connected to the disease.
But health officials say other factors may be at play, too. One suspected problem is the widespread use of acellular pertussis vaccines, which cause fewer negative reactions in patients than earlier vaccines but may not provide the long-lasting immunity.