1. Public Health Case Study Mark Wathen Is This Really Okay for Me? A Public Health Statistical Analysis CDC’s 2005 Science Ambassador Program

2. Case Study Outline I. Public Health II. Surveillance III. Epidemiological Studies A. Calculations 1. Prevalence 2. Incidence 3. Risk Ratio IV. Prevention

3. Public Health  Is the science and art of preventing disease, prolonging life, and promoting health through the organized efforts of society including Monitoring disease and other health- related conditions (surveillance); and Identifying and quantifying important trends (epidemiology).

4. Surveillance  Is the monitoring of the occurrence of a disease or other health-related condition. Active surveillance  Actively searching for people with a disease or condition. Passive surveillance  Dependent on reporting from external sources.

5. Epidemiology  The study of the distribution, determinants, and deterrents of disease or other health-related conditions. Distribution is the frequency and patterns in terms of person, place, and time (who, where, and when). Determinants are factors that cause or contribute to a disease or condition. Deterrents are factors that prevent or reduce the chance of developing a disease or condition.

6. Prevalence  The proportion of a population that has a disease or health-related condition during a specific time. total population Prevalence = Number of people affected ______________________________________

7. Case Study  February 2004.  School nurse reported 39 cases of the flu in the high school.  Age of students 14–18 years  Total of 780 students in the school.  What was the prevalence of the flu for this high school?

8. Prevalence Calculation  Report who, where, and when. Population: Students aged 14–18 Place: High school Time: February 2004 Prevalence = 39 students with flu total population Prevalence = Number of people affected ______________________ 780 total students _____________________ Prevalence = 5 out of every 100 students had the flu. Can also be said 5% of students had the flu.

9. Case Study — Continued  Results 5 out of 100 students had the flu.  Monitor the situation during the month of March (2004).  9 new cases of flu within the school.  Calculate the incidence during this time period.

10. Incidence  The rate at which new disease or health-related condition occurs in a population. Incidence = Number of newly affected people ___________________________________ population at risk Incidence = 9 new cases of flu ___________________ (780 – 39) population at risk Incidence = 12 out of 1,000 students had the flu at the high school

11. Case — Study Continued  Results — 12 out of 1,000 students had the flu.  What is the cause?  A teacher mentioned seeing students coughing and sneezing around the candy machine.  The nurse investigated to see if there was any correlation between the candy machine and having the flu.

12. Case Study — Continued  The nurse monitored 200 students over a 1-month period.  120 used the candy machine.  12 cases of flu occurred in this group.  5 cases of flu appeared in the group that didn’t use the candy machine.  So was there a risk in using the candy machine?

13. Prevalence Ratio  Ratio of prevalence of disease in the exposed group divided by the prevalence of disease in the unexposed group.

14. Prevalence Ratio 2  2 Table DiseaseNo DiseaseTotal Exposed ABA+B Unexposed CDC+D Total A+CB+DA+B+C+D Prevalence Ratio = A / (A+B) _______ C / (C+D)

15. Prevalence Ratio 2  2 Table FluNo FluTotal Exposed to machine 12108120 Unexposed 57580 Total 17183200 Prevalence Ratio = 12 / (120) _______ 5 / (80) = 1.6

16. Analysis of Prevalence Ratio  If value >1, then exposure is producing outcome.  If value =1, no connection between exposure and outcome.  If value <1, exposure is prohibiting the outcome.  In the case study, the prevalence ratio was 1.6. Therefore, students using the candy machine were 1.6 times as likely to get the flu as students not using the candy machine.

17. Prevention  The final step of public health is prevention.  If you were the school nurse, what prevention program would you develop for your school?

18. Summary  Pubic health is the science and art of preventing disease, prolonging life, and promoting health through the organized efforts of society.  There are three parts to public health: Surveillance, which monitors diseases and health-related conditions. Epidemiology, which identifies and quantifies trends (prevalence, incidence, and risk ratio). Prevention, which includes programs that inform and educate the population at risk.

19. References 1. “Public Health Measurement and Research Design” PowerPoint presentation by Alison Nair, CDC Ambassador Program, June 2004. 2. Oleckno, W.A. Essential Epidemiology: Principles and Applications. Waveland Press, Inc., Long Grove, Illinois, 2002.