Surveillance and Epidemiology of the Pertussis Resurgence in the United States, 1990-2010.

Abstract

After a period of successful control, pertussis or whooping cough has, in the past decade, had large nationwide epidemics with a new adolescent risk-group. The surveillance confirmation criteria for pertussis included DNA testing by polymerase chain reaction (PCR) beginning in 1997, which is more sensitive than the culture gold-standard laboratory test, especially in adolescents and adults. This dissertation uses surveillance date from the state of Michigan to retrospectively assess the internal validity of reported pertussis surveillance cases. Data from the United States Centers for Disease Control and Prevention evaluated characteristics predictive of high incidence counties. Michigan pertussis records (2000 - 2010) were evaluated according to the clinical case definition; a third included positive PCR results. Confirmed and probable cases comprised 69.4% of the data, and another 14% could have been confirmed had an adequate cough length been reported. An odds of insufficient cough duration was reported among PCR positive cases, 2.9 (95% CI: 1.57 - 2.79) times greater than in those without PCR positive results. Similar findings were observed for cases confirmed by culture and epidemiologic linkage. These findings show confirmatory criteria are frequently given precedence over the clinical case definition. We recommend that the case definition be more internally consistent with regard to the role of positive laboratory results. This dissertation illustrates that the current pertussis surveillance case definition has high internal validity. Surveillance cases need to be held to more stringent criteria for verification than for medical diagnosis, since it is the basis for allocation of time and resources for case and outbreak investigation. County-level regression analysis of socio-structural risk-factors in national United States pertussis data (1990 - 2008), indicated that denser counties with a higher prevalence of healthcare barriers and poor child health were associated with decreased pertussis incidence. We observed an element of disease risk associated with county-level factors. Our findings could be explained either by low rates of disease or a less developed surveillance structure. Further research to identify the county elements driving the risk differential is needed to tailor both vaccination and outbreak response efforts to local needs.PHDEpidemiological ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102294/1/jkknapp_1.pd