Whoop, where it is? Pertussis in the United States from 2000-2005

Background: Among diseases for which universal childhood vaccination is recommended, pertussis is one of the least controlled. Since the 1980s, reported pertussis cases have increased.

Method: Cases were reported to CDC's National Notifiable Diseases Surveillance System, using Council of State and Territorial Epidemiologists defined probable and confirmed cases.

Results: From 2000-2005, 88,308 pertussis cases were reported; the average annual incidence was 5.1/100,000 population. There was a three-fold increase in incidence between 2000 and 2005 (2.7/100,000 versus 8.7/100,000). The incidence was highest among infants <6 months (average annual 116.0/100,000) with a two-fold increase from 2000 to 2005 (88.0/100,000 versus 160.8/100,000). Incidence in adolescents increased from 7.0/100,000 in 2000 to 18.4/100,000 in 2005; similarly, adult incidence increased from 0.78/100,000 in 2000 to 3.6/100,000 in 2005. During this time, there was an increase in use of polymerase chain reaction (PCR) testing to confirm pertussis cases. The percentage of PCR confirmed cases increased from 18% in 2000 to 29% in 2005 whereas culture confirmed cases declined from 23% in 2000 to 9% in 2005. This change in testing was similar for infants (PCR: 21% in 2000 to 39% in 2005; Culture: 39% in 2000 to 24% in 2005) and adolescents/adults (PCR: 13% in 2000 to 19% in 2005; Culture: 15% in 2000 to 6% in 2005).

Conclusions: Pertussis cases increased substantially from 2000-2005. This increase paralleled use of PCR testing, suggesting that the increase may be due, at least partially, to greater ability to diagnose pertussis rather than a true increase in pertussis cases.