Pertussis Cases in California Reach 55-Year High

The California Department of Public Health (CDPH) reports that as of Sept. 14, 2010, there have been 4,017 confirmed, probable and suspect cases of pertussis (whooping cough) reported in 2010 for a state rate of 10.3 cases per 100,000.

According to data from the CDPH, 3,985 of reported cases had disease onset in 2010, with 183 new cases reported this week, compared to 234 in the prior week. This is the most cases reported in 55 years when 4,949 cases were reported in 1955 and the highest incidence in 48 years when a rate of 10.9 cases/100,000 was reported in 1962. Previously, the peak was in 2005 when there were 3,182 cases reported.

Of the 44 percent of cases with known hospitalization information, 196 (11.2 percent) cases have been hospitalized; 115 (57 percent) of hospitalized cases were infants <3 months of age and 146 (74 percent) were infants <6 months of age.

Nine deaths have been reported; eight fatalities were infants <2 months of age at time of disease onset and had not received any doses of pertussis-containing vaccine and the remainder was an ex-28 week preemie that was 2 months of age and had received the first dose of DTaP only 15 days prior to disease onset. The majority of infant cases in 2010 have occurred in infants <3 months of age.

Rates are highest in infants <6 months of age (184 cases/100,000), in children aged 7-9 years (33 cases/100,000) and adolescents aged 10-18 years (24 cases/100,000). The majority of adolescent cases are in 10-11 year-olds. Overall rates by race/ethnicity are highest in whites (9.8/100,000), however age-specific rates indicate that the highest rates are seen in Hispanic infants <6 months of age (229/100,000).

The median case rate by county is 9.1 cases per 100,000 (range 0-128).