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Mission and Roles

  • Promote healthy lifestyles and prevent diseases and conditions affecting our communities’ wellbeing, quality of life, and economies.
  • Epidemiology is the method used to find the causes of health outcomes and diseases in populations. In epidemiology, the patient is the community and individuals are viewed collectively. Epidemiology is the study (scientific, systematic, and data-driven) of the distribution (frequency, pattern) and determinants (causes, risk factors) of health-related states and events (not just diseases) in specified populations. It is also the application of this study to the control of health problems.
  • Examples of epidemiological Investigations include
    • contagious diseases like influenza (flu), COVID-19, or sexually transmitted infections
    • food or waterborne illnesses
    • injuries like homicides and domestic violence
    • non-infectious diseases (cancer, diabetes, heart disease)
    • environmental exposures (lead, air pollution impacting respiratory illnesses)
    • natural disasters and acts of terrorism

Investigations usually involve teams of disease investigators that contact affected individuals to ask questions about their exposure to factors associated with the development of a disease or condition.



Delaware County Population

  • Delaware County has 183.8 square miles of land area. It is the 65th largest county in Pennsylvania by total area. The county has the second largest number of persons per square mile (3,040.50). Delaware County is bordered by New Castle County, Delaware, Philadelphia County, Pennsylvania, Chester County, Pennsylvania, Gloucester County, New Jersey, and Montgomery County, Pennsylvania.
  • Delaware County 2021 total population was 573,849. The county has the fifth largest county population in Pennsylvania. Age groups 55 to 59, 15 to19, and 10 to 14 accounted for the largest number of persons in the county.
  • In 2021, White or Caucasian (67.4%), African American (23.4%), Asian (6.5%), American Indian and Alaska Native (0.20%), and Native Hawaiian and Other Pacific Islander (0.10%) accounted for the county’s population. Hispanic or Latinos represented 4.5%. From 2016-2020, 10.60% of the county population was foreign born.
  • For additional information on Delaware County’s population visit:

An important responsibility of DCHD’s epidemiology and disease surveillance team is tracking and responding to reports of communicable disease in Delaware County. For healthcare practitioners and healthcare facilities, all diseases are reportable within 5 working days, unless otherwise noted. For clinical laboratories, all diseases are reportable by next work day, unless otherwise noted.

Here is the List of Reportable Diseases and reporting deadlines by condition in Pennsylvania: https://www.health.pa.gov/topics/Reporting-Registries/Pages/Reportable-Diseases.aspx (PA Code, Title 28, Chapter 27O | Updates 1 & 2 requiring electronic reporting.)

Other Resources

Leading causes of injuries and death in Delaware County: https://wisqars.cdc.gov/fatal-leading

Years of Potential Life Lost (YPLL): https://wisqars.cdc.gov/ypll

Contact Us

  •   201 West Front Street,
         Media, PA 19063
  •   8:30AM - 4:30PM
           Monday - Friday
  •   610-891-4000
  • webmaster@co.delaware.pa.us

About Delaware County

Delaware County, presently consisting of over 184 square miles divided into forty-nine municipalities is the oldest settled section of Pennsylvania.

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