Shigella Infections in Maryland

Transcription

1 Shigella Infections in Maryland Emily Lu, MPH Candidate PHASE Intern Johns Hopkins Bloomberg School of Public Health Janet Holbrook, PhD, MPH Epidemiology Department, Johns Hopkins University Pat Ryan, MS Maryland Department of Health and Mental Hygiene Emerging Infections Program

2 Background Shigella bacteria: gram-negative, nonmotile, nonencapsulated bacilli Symtoms: fever, fatigue, watery diarrhea, may progress to cramps and tenesmus Complications: severe dehydration, intestinal perforation, septicemia, seizures, and hemolytic uremic syndrome (HUS) In the U.S., among pathogens commonly transmitted through food, Shigella is the 3 rd most common cause of bacterial infections after Salmonella and Campylobacter.

3 Research Questions Do the characteristics of the population affected by Shigella infections vary over time from 1998 to 2002? Why was there a sudden increase in the incidence rate of Shigella infection during 2002?

4 Maryland s Foodborne Diseases Active Surveillance Network (FoodNet) Part of CDC s Emerging Infections Program Population-based active surveillance system for foodborne diseases caused by bacterial and parasitic infections Laboratory-confirmed cases Pathogens under surveillance: Campylobacter, E. coli 0157, Listeria monocytogenes, Salmonella, Shigella, Yersinia enterocolitica, Vibrio, Cryptosporidium and Cyclospora

5 Methods Descriptive analysis of race distribution, sex ratio, % hospitalization, mean and median age of Shigella cases Incidence rates of Shigella infection calculated using census data from Maryland Department of Planning Chi-square test for trend Multiple logistic regression analysis

6 Maryland Counties

7 Results

8 Shigella Infections in Baltimore Metro Area of Maryland, % (1296) 100% (1040) 100% (62) 100% (81) 100% (55) 100% (58) Total 2.0% (26) 1.4% (15) 1.6% (1) 4.9% (4) 3.6% (2) 6.9% (4) Shigella unspecified 91.2% (1182) 97.7% (1016) 64.5% (40) 77.8% (63) 56.4% (31) 55.2% (32) Shigella sonnei 6.0% (78) 0.8% (8) 27.4% (17) 14.8% (12) 36.4% (20) 36.2% (21) Shigella flexneri 0.8% (10) 0.1% (1) 6.5% (4) 2.5% (2) 3.6% (2) 1.7% (1) Shigella boydii Total Percent (counts) By serogroup

9 Shigella Infections in Baltimore Metro Area by Month 2002 vs Shigella Infections Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

10 Shigella Incidence Rates in Baltimore Metro Area of Maryland Infections/100,000 Population Year χ2 (df=1) =2.9 x 103, p <

11 Incidence rates of Shigella infections in Baltimore Metro Area of Maryland, By race Incidence rate/100, p value** White <.0001 Black <.0001 Other* *Other: Asian & other. (Excluded race unknown) **χ2 test for trend, 4 degree of freedom.

12 Age Distribution Incidence of Shigella Infections in Baltimore Metro Area by Age Category, incidence per 100,000 population >=60 Age group (years)

13 Age Distribution (cont d) Incidence of Shigella Infections in Baltimore Metro Area by Age Category, incidence per 100,000 population >=60 Age group (years)

14 Incidence rates of Shigella infections in Baltimore Metro Area of Maryland, By jurisdiction Incidence rate/100, P value* Anne Arundel <.0001 Baltimore City <.0001 Baltimore County <.0001 Carroll Harford <.0001 Howard *χ2 test for trend, 4 degrees of freedom.

15 Shigella Incidence Rates by Race and Age Category in Baltimore City, 2002 incidence per 100,000 population >=40 White Black Other age category (years)

16 Shigella Incidence Rates by Race and Age Category in Baltimore County, 2002 incidence per 100,000 population >=40 White Black Other age category (years)

17 Multiple Logistic Regression Analysis Year (2002 vs )* Age category** Adj. Odds Ratio (95% CI) (14.09 to 18.52) 0.57 (0.56 to 0.59) P Value < < Year (2002 vs )* Age category*** Year*Age category (40.34 to 70.91) 0.77 (0.72 to 0.82) 0.68 (0.63 to 0.73) < < < *Grouped 1998, 1999, 2000, & 2001 together as the reference group and 2002 as the comparison year. **Age divided into categories: 0-4 years=1, 5-9 years=2, years=3, years=4, years=5, years=6, years=7, & 60 years or above=8.

18 Multiple Logistic Regression Analysis (cont d) Year (2002 vs )* Race (0=white, 1=black) Adj. Odds Ratio (95% CI) (15.73 to 21.03) 7.64 (6.71 to 8.70) P Value < < Year (2002 vs )* Race (0=white, 1=black) Year*Race 5.18 (4.12 to 6.50) 1.72 (1.32 to 2.25) 7.07 (5.16 to 9.67) < < < *Grouped 1998, 1999, 2000, & 2001 together as the reference group and 2002 as the comparison year.

19 Conclusion and Public Health Implication Shigella infections affecting mostly African American children < 5 years old in 2002 Age group with highest incidence rate observed is in agreement with day care attendees Crowded living conditions, dilapidated housing and poverty may also influence the rates of Shigella infection To treat or not to treat Vaccine (not currently available) Prevention target: hygiene education (hand washing) Detection bias An underestimate of true burden

20 Acknowledgments Pat Ryan, MS Janet Holbrook, PhD David Blythe, MD, MPH Melanie Megginson, MPH Dipti Shah, MPH Michel Ibrahim, MD, PhD, MPH Ayanna Fews, MBA Frances Burman Marie Diener-West, PhD Rosa Crum, MD, MHS