BACKGROUND: Pertussis, or whooping cough, is a vaccine preventable disease caused by the bacterium Bordetella pertussis. Pertussis infection causes violent coughing and can be life-threatening to infants. Pertussis cases have been increasing in the United States since the 1980s. Pennsylvania has reported 600-1900 pertussis cases annually over the past 5 years. Pennsylvania pertussis cases reported between 2011 and 2015 were compared to socio-economic characteristics of the census tracts in which they live to determine which characteristics are more highly linked to increased pertussis morbidity.
METHODS: In Pennsylvania, pertussis cases are investigated and entered into an electronic disease data entry system, PA-NEDSS. PA-NEDSS geocodes cases’ home addresses and assigns them to a census tract. Census tract socio-economic data were obtained from census.gov. The data were analyzed using SAS software. Percentages of persons exhibiting specific socio-economic characteristics in each census tract were compared to pertussis incidence rates in the census tract using Pearson correlation to determine significance of association.
RESULTS: Several socio-economic characteristics were found to be significantly associated with higher incidence of pertussis cases with a p-value of 0.05 or lower including: low poverty levels, high percentages of college graduates, higher levels of children in kindergarten through twelfth grades attending private schools, higher rates of private medical insurance, and higher rates of persons aged 5 to 14 in the population. Socio-economic characteristics significantly associated with lower incidences of pertussis cases included: high poverty levels, low percentages of college graduates, higher levels of children in kindergarten through twelfth grades attending public schools, and higher rates of public health insurance. Characteristics unrelated to pertussis incidence included: rates of persons speaking limited English in the household, rates of children under 5 years of age and rates of persons over 65 years of age.
CONCLUSIONS: In Pennsylvania, areas in which wealthier, more highly educated persons live tend to have a higher incidence of pertussis. Conversely, census tracts which have higher rates of persons living below the poverty level, more persons attending public schools and on public medical insurance have lower incidences of pertussis. It is important to identify social and economic characteristics of communities with an increased incidence of disease to determine the best means of disease prevention and outreach in these communities.