BACKGROUND:
Despite high rates of immunization among infants and children, reported cases of pertussis in upstate New York increased significantly during 2003. A total of 932 cases were reported in 2003 compared to 445 in 2002 and 176 in 2001.

OBJECTIVE:
Describe trends and possible contributing factors to the recent increased incidence of pertussis in upstate New York.

METHOD:
Use of data from the disease reporting database and line lists from recent outbreaks to analyze trends in incidence of pertussis.

RESULT:
The majority of cases occurred during the fall. Fifteen of the 57 counties across the state reported a significant increase in cases. Ten of those counties experienced outbreaks. Most cases were fully or partially immunized individuals. Thirty-seven percent of the cases occurred in the 10-14 year age group. Fifty percent of the cases were confirmed by PCR, 27% were confirmed by epi-link, and 23% were probable. No deaths were reported, but about 10% of the cases required hospitalization. Prompt response by local health officials to initiate outbreak control measures and appropriate communication with physicians and the public was a key element in outbreak response.

CONCLUSION:
We describe a significant increase in pertussis throughout upstate New York during 2003. Possible contributing factors include waning immunity, no adult pertussis vaccine available in US, low rate of vaccine efficacy, increased physician and public awareness, availability of PCR rapid testing, and the 1996 change in the clinical case definition.

LEARNING OBJECTIVES:
Participants will be able to identify:
¨The importance of following outbreak control guidelines.
¨The significance of surveillance in monitoring trends in pertussis incidence.
¨Possible contributing factors to increased incidence of pertussis.