Georgia epidemiology report, Vol. 24, no. 5 (May 2008)

May 2008

volume 24 number 05

FoodNet

Introduction What is FoodNet? The Foodborne Diseases Active Surveillance Network (FoodNet) is the foodborne disease component of the Centers for Disease Control and Prevention's (CDC) Emerging Infections Program. FoodNet is a collaborative project among CDC, 10 sites (states or parts of states), the United States (US) Department of Agriculture (USDA), and the Food and Drug Administration (FDA). FoodNet began in 1996 in 5 sites, including Georgia, and now includes 10 (Figure 1), covering 44.5 million people, or 15% of the US population. FoodNet provides accurate estimates of foodborne illness through laboratory-based active surveillance and epidemiologic studies. FoodNet sites conduct active surveillance for seven bacteria that cause foodborne illness (Campylobacter, Listeria, Salmonella, Shigella, Shiga toxin-producing Escherichia coli (STEC), including O157, Vibrio, and Yersinia), two parasitic organisms (Cyclospora and Cryptosporidium), and one syndrome (hemolytic uremic syndrome (HUS)).

Figure 1. Map of FoodNet/Emerging Infections Program sites 2.

Active versus Passive Surveillance Most foodborne disease surveillance systems consist of passive "notifiable disease" reports, that are mandated by State laws. Clinicians who treat patients with foodborne illness, and clinical laboratories that identify causes of foodborne illness from submitted specimens, report their findings to local and state health departments. The health departments then report to CDC. Information from this passive method may be incomplete. To identify all cases of illness due to infection with the pathogens under surveillance, FoodNet personnel in all sites contact about 650 clinical laboratories (114 in Georgia) to determine whether the laboratory has isolated one of the FoodNet pathogens. Each clinical laboratory is audited at least twice yearly to ensure that FoodNet captures every case.
FoodNet Objectives and Activities FoodNet has four primary objectives: 1.) Determine the burden of foodborne illness in the US ; 2.) Monitor trends in the burden of specific foodborne illness over time; 3.) Attribute the burden of foodborne illness to specific foods and settings; and 4.) Develop and assess interventions to reduce the burden of foodborne illness. The active surveillance data described above, along with various working groups and special epidemiologic studies, are used to achieve these objectives. In addition, the data are used to design studies to answer specific research questions. For example, a recent FoodNet study in which Georgia participated explored why Salmonella infections are more common in infants than in other age groups. The study results identified exposures to reptiles, and/or riding in a shopping cart next to raw meat or poultry to be associated with Salmonella infection in infants, while having been breast-fed had a protective effect (1).

FoodNet 2007 Surveillance Summary(2) Methods Annually, FoodNet epidemiologists and statisticians analyze the preliminary surveillance data from the preceding year, and compare with data from previous years, and with the Healthy People 2010 objectives (3). CDC epidemiologists have developed a statistical model (negative binomial) to account for the increases in population over time and variation in pathogen-specific disease incidence among different sites (2). The incidence data are used to monitor trends over time, which include monitoring progress toward national health goals, and evaluating results of food safety interventions. The estimated changes in incidence between 2007 and two baseline periods (19961998 and 2004-2006) are calculated as relative rates. The more recent baseline period was used to evaluate any recent changes in relative incidence that may not be apparent using the earlier baseline period. A large outbreak caused by a FoodNet pathogen can affect the incidence data in a given year.

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Results The estimated incidence of Campylobacter, Listeria, Salmonella, Shigella, STEC O157, Vibrio, and Yersinia infections did not change significantly compared to the 2004-2006 period (Figure 2), but, the
estimated incidence in Cryptosporidium infections increased 44% (95% CI 8%-91%). If the 1996-1998 baseline period is used, the
resulting relative rates demonstrate a decrease in Yersinia*, Listeria, Shigella*, Campylobacter, and STEC infections in 2007, with no significant changes in Cryptospridium* and Vibrio infections (Figure 3). Relative rates for the less common conditions, Cyclospora and HUS, are not presented, but incidence rates can be seen in Table 1.
Comparing the incidence rates of each FoodNet pathogen for
Georgia, FoodNet overall, and the Healthy People 2010 objective
(Table 1), in 2007 Georgia rates for Shigella and Salmonella were the highest of any FoodNet site. Incidences of STEC and Campylobacter in Georgia remain lower than those of most other FoodNet sites, and
are below the Healthy People 2010 objectives. Outbreak-associated
cases of STEC O157 comprised 15.8% of total reported cases, and
5.4% of Salmonella cases were associated with outbreaks. These proportions are similar to data from previous years.
*Data not shown

The high rate of Shigella infections in Georgia in 2007 represents outbreaks in young children that cycle over years, and affect different parts of the country in different years. It is unlikely that the rates of any other FoodNet pathogens in Georgia were driven by outbreaks in 2007. It is possible the increased incidence in Cryptosporidium represents improved testing methods or improved reporting to public health. In addition, a newly approved drug (nitazoxanide) for treatment of this parasite may be leading clinicians to test more frequently. For more information about Cryptosporidium epidemiology in Georgia, see below.

Conclusions Many of the significant declines in incidence of these foodborne pathogens occurred before 2004, and, in 2007, incidence of most pathogens did not vary significantly from a 2004-2006 baseline period. FoodNet sites overall are not approaching the Healthy People 2010 objectives for Salmonella, but are closer in achieving the goals for STEC O157, Listeria, and Campylobacter. In Georgia, Salmonella incidence remains the highest of any FoodNet site. This may be due to a specific animal or environmental niche in the southern parts of the state (where the rates are particularly high).

Table 1. Incidence (per 100,000 population) of laboratory-confirmed bacterial and parasitic infections reported for Georgia, FoodNet overall, compared to the national health objective, 2007.

Pathogen

Georgia FoodNet

FoodNet overall

Healthy People 2010*

Campylobacter

7.29

12.79

12.30

Listeria

0.33

0.27

0.24

Salmonella

21.78

14.92

6.80

Shigella

17.39

6.26

NA

STEC O157

0.50

1.20

1.00

STEC non-O157

0.44

0.57

NA

Vibrio

0.25

0.24

NA

Yersinia

0.46

0.36

NA

Cryptosporidium

2.45

2.67

NA

Cyclospora

0.03

0.03

NA

HUS**

1.00

2.01

0.90

Adapted from reference 2

*NA denotes no objective exists for pathogen

**Incidence is limited to children under the age of 5 years

Division of Public Health http://health.state.ga.us
S. Elizabeth Ford, M.D., M.B.A., F.A.A.P.
Acting Director State Health Officer

Martha N. Okafor, Ph.D. Deputy Director
John M. Horan, M.D., M.P.H. State Epidemiologist Epidemiology Section
http://health.state.ga.us/epi

Georgia Epidemiology Report Editorial Board
Carol A. Hoban, M.S., M.P.H. Editor Kathryn E. Arnold, M.D.
Cherie Drenzek, D.V.M., M.S. John M. Horan, M.D., M.P.H. S. Elizabeth Ford, M.D., M.B.A., F.A.A.P. Angela Alexander - Mailing List Jimmy Clanton, Jr. - Graphic Designer
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Georgia Department of Human Resources
Division of Public Health

Two Peachtree St., N.W. Atlanta, GA 30303-3186 Phone: (404) 657-2588
Fax: (404) 657-7517
Please send comments to: gaepinfo@dhr.state.ga.us

Cryptosporidiosis

Cryptosporidium is a parasite that causes diarrhea and abdominal cramps. The incubation period ranges from 2 to 10 days, and the duration of illness can be 2 weeks or longer. The infection is difficult to treat in immunocompromised patients and may become chronic in AIDS patients. Although one may become infected by eating contaminated foods (especially produce) or coming in contact with various types of animals, the most commonly implicated source of infections is treated water venues such as swimming pools. Cryptosporidium is frequently resistant to chlorine, so infection may occur after swimming in chlorinated water. Oocystes can survive in the recommended chlorine levels for swimming pools (13 ppm free chlorine) for many days. Other barriers besides chlorination must be in place to prevent outbreaks of cryptosporidiosis, such as improved operator training and community education about healthy swimming practices. Examples of such messages include requiring diapered children to wear special swim pants and avoiding swallowing water while swimming.
A recent FoodNet case-control study identified a number of significant risk factors for infection with Cryptosporidium, including international travel, contact with cattle, and recreational water exposure (4). This last finding is important during summer months when recreational water activities are at their peak. Reported numbers of infections are increased during the summer (Figure 4).
In 2007, there were three clusters of swimming-associated cryptosporidiosis reported in Georgia. Two were associated with private homes and one with a neighborhood pool. It is likely that a greater number of cases and outbreaks are actually occurring, but are not being identified or reported. A pilot interview study completed in Georgia during 2007 identified

Number of cases Number of cases Jan FJeabn FMearb AMparr MAapyr JMuany JJuuln AJuugl SAeupg SOectp NOocvt DNeocv Dec

that of 32 cases interviewed by public health staff during the summer months, over half had exposure to recreational water during the 2 weeks before illness onset. The pilot was limited by the fact that only slightly over one third of reported cases were interviewed. In contrast to the pattern of increased case numbers reported nationally described (2,5), there were actually fewer cases of Cryptosporidium reported in Georgia in 2007 (247) than in 2006 (275), but these numbers are both significantly higher than the previous 3-year mean. The week of May 19-25 is the fourth annual Recreational Water Illness Prevention Week http://www.cdc.gov/healthyswimming/ rwi_prevention_week.htm. The Georgia Division of Public Health offices have educational information available for pool operators and the general public to help prevent water-related illnesses, including Cryptosporidium infection, this summer.

Figure 4. Number of Cryptosporidium infections reported by month, Georgia, 2004-2007

5050 4040 3030 2020 1010
00

20024004 20025005 20026006 20027007

MoMnothnth

This article was written by Melissa Tobin-D'Angelo, M.D., M.P.H.

Resources FoodNet and Food Safety www.cdc.gov/foodnet www.health.state.ga.us/EIP www.foodsafety.gov www.fightbac.org
Recreational Water Safety www.cdc.gov/healthyswimming http://www.cdc.gov/healthyswimming/rwi_prevention_
week.htm http://health.state.ga.us/programs/envservices/pools.asp

References 1. Jones TF, et al. A Case-Control Study of the Epidemiology of Sporadic
Salmonella Infection in Infants. Pediatrics 2006; 118:2380-7. 2. Centers for Disease Control and Prevention. Preliminary FoodNet Data
on the Incidence of Infection with Pathogens Transmitted Commonly Through Food--10 States, 2007. MMWR 2008;57 (14): 366-370. 3. http://www.healthypeople.gov/document/html/tracking/OD10.htm. Accessed 4-30-08. 4. Roy, SL et al. Risk Factors for Sporadic Cryptosporidiosis among Immunocompetent Persons in the United States from 1999 to 2001. J. Clin. Microbiol. 2004 42: 2944-2951 5. http://www.cdc.gov/healthyswimming/pdf/Crypto_Alert_for_Health_ Professionals.pdf Accessed 4-30-08.

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The Georgia Epidemiology Report Epidemiology Branch Two Peachtree St., NW Atlanta, GA 30303-3186

PRESORTED STANDARD U.S. POSTAGE
PAID ATLANTA, GA PERMIT NO. 4528

May 2008

Volume24Number05

Reported Cases of Selected Notifiable Diseases in Georgia, Profile* for February 2008

Selected Notifiable Diseases
Campylobacteriosis Chlamydia trachomatis Cryptosporidiosis E. coli O157:H7 Giardiasis Gonorrhea Haemophilus influenzae (invasive) Hepatitis A (acute) Hepatitis B (acute) Legionellosis Lyme Disease Meningococcal Disease (invasive) Mumps Pertussis Rubella Salmonellosis Shigellosis Syphilis - Primary Syphilis - Secondary Syphilis - Early Latent Syphilis - Other** Syphilis - Congenital Tuberculosis

Total Reported for February 2008
2008 46 179 9 0 36 74 17 4 11 1 0 2 0 1 0 54 79 7 44 22 62 0 28

Previous 3 Months Total Ending in February

2006 2007 2008

112

101

123

9666

10865

5317

46

38

37

4

5

2

150

127

131

4619

4401

2083

38

38

58

11

15

12

30

38

39

3

10

9

1

0

1

3

9

4

1

0

0

7

5

4

0

0

0

240

322

266

170

300

322

27

23

12

117

126

140

90

114

89

256

259

237

3

2

1

105

110

108

Previous 12 Months Total Ending in February

2006 2007 2008

619

571

698

34792

40925

38201

178

271

236

31

44

42

721

683

682

16601

20081

15952

110

118

145

109

62

64

167

203

153

37

43

41

7

7

11

14

23

22

2

4

0

48

28

15

0

0

0

1956

1906

1962

737

1433

1661

130

120

95

540

488

580

411

403

402

994

1030

1109

5

9

8

502

518

470

* The cumulative numbers in the above table reflect the date the disease was first diagnosed rather than the date the report was received at the state office, and therefore are subject to change over time due to late reporting. The 3 month delay in the disease profile for a given month is designed to minimize any changes that may occur. This method of summarizing data is expected to provide a better overall measure of disease trends and patterns in Georgia.
** Other syphilis includes latent (unknown duration), late latent, late with symptomatic manifestations, and neurosyphilis.
AIDS Profile Update

Report Period
Latest 12 Months**:
2/06-1/07
Five Years Ago:
2/02-1/03

Disease

Total Cases Reported*

Classification <13yrs

>=13yrs Total

HIV, non-AIDS

32

2,944

2,976

AIDS

8

1,743

1,751

HIV,

-

non-AIDS

AIDS

7

1,885

1,892

Percent Risk Group Distribution

Female MSM

IDU

MSM&IDU HS

Unknown

Perinatal

Race Distribution

White Black

Hispanic

26

21

2

1

4

72

<1

22

73

4

26

26

2

1

8

63

<1

19

73

5

-

-

-

-

-

-

-

-

-

-

28

36

7

2

16

38

<1

19

75

5

Other 0 3 1

Cumulative: HIV, non-AIDS 217

11,178

11,395

32

27

6

2

11

52

2

21

74

4

1

07/81-1/07 AIDS

238

32,241

32,479

20

44

15

5

14

22

<1

30

66

3

1

Yrs - Age at diagnosis in years

MSM - Men having sex with men

IDU - Injection drug users

HS - Heterosexual

* Case totals are accumulated by date of report to the Epidemiology Section ** Due to a change in the surveillance system, case counts may be artificially low during this time period

***HIV, non-AIDS was not collected until 12/31/2003

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