KEYWORD1:
Epidemiology, Pertussis, Surveillance, Incidence

BACKGROUND:
California’s pertussis incidence rate has been rising gradually since the mid-1970s. In recent years, adults and infants under four months of age have represented a growing proportion of reported pertussis cases. Unfortunately, no vaccine is currently available to effectively prevent pertussis in these age groups. Further understanding of the epidemiology of pertussis is necessary to plan preventive interventions.

OBJECTIVE:
To investigate the increase in pertussis disease in California, especially among infants.

METHOD:
Pertussis is a reportable condition in California. Case investigation form data from 1990 to 2002 were analyzed. Incidence rates were calculated using 1990/2000 census data and intercensal population estimates.

RESULT:
In 1990, 468 cases of pertussis were reported in California (1.6/100,000). Incidence in children <1 yr of age was 50.8 and was highest in Hispanic infants, 54.9. Seventy nine percent of cases <4 months of age (n=208) were hospitalized and one one-month-old infant died. In 2001, 706 cases of pertussis were reported (2.0/100,000). Incidence in children <1 yr of age was 51.0 and was highest in Hispanic infants, 60.0. Eighty four percent of cases <4 months of age (n= 246) were hospitalized and five Hispanic and Native American infants <4 months of age died.

CONCLUSION:
The high rates of pertussis occurring among infants too young to receive three doses of pertussis-containing vaccine suggest that pertussis continues to circulate widely throughout California. Prevention and control efforts should continue to be directed at maintaining high pertussis vaccination rates, managing pertussis cases and their contacts, and minimizing infant exposures to persons with cough illnesses.
LEARNINGOBJECTIVES:
To understand the epidemiology of pertussis in a large state.