Georgia epidemiology report, Vol. 19, no. 7 (July 2003)

July 2003

volume 19 number 07

Division of Public Health http://health.state.ga.us
Kathleen E. Toomey, M.D., M.P.H. Director
State Health Officer
Epidemiology Branch http://health.state.ga.us/epi
Paul A. Blake, M.D., M.P.H. Director
State Epidemiologist
Mel Ralston Public Health Advisor
Georgia Epidemiology Report Editorial Board
Carol A. Hoban, M.S., M.P.H. - Editor Kathryn E. Arnold, M.D.
Paul A. Blake, M.D., M.P.H. Susan Lance-Parker, D.V.M., Ph.D. Kathleen E. Toomey, M.D., M.P.H.
Angela Alexander - Mailing List Jimmy Clanton, Jr. - Graphic Designer

Listeria surveillance
Introduction
Listeria monocytogenes is an uncommon cause of illness in the general population. Nonetheless, an estimated 2,500 cases occur in the United States (U.S.) yearly, with 500 deaths/year (case fatality rate 20%). Investigations of both outbreaks and sporadic cases have shown that transmission is most likely food-borne (2). The Foodborne Diseases Active Surveillance Network (FoodNet) data demonstrate listeriosis to be the food-borne illness with the highest rates of hospitalization (90% in 2001) (1). (FoodNet is part of the Centers for Disease Control and Prevention's (CDC's) Emerging Infections program, which does active surveillance for food-borne disease in 10 areas of the country.)
L. monocytogenes is a gram-positive rod-shaped bacterium. It is present in the environment in soil, water, and vegetation, and is an important cause of zoonoses. It differs from many other food-borne bacteria in being able to multiply in refrigerated contaminated foods. L. monocytogenes has been found in a variety of ready-to-eat foods such as hot dogs and deli meats. Unpasteurized dairy foods such as milk and soft cheeses (feta, Mexican style or queso fresco) are other common sources. Cases of human disease have also been associated with fresh fruits and vegetables, smoked seafood, pate, coleslaw, and a variety of other foods. In addition to transmission through food, mother to child transmission occurs, either transplacentally or during passage through the infected birth canal. A rare mode of transmission is direct contact with infectious material.
Clinical aspects
Listeriosis has multiple clinical manifestations. The persons at highest risk for infection are the elderly, neonates, pregnant women, and immunocompromised individuals. In adults and neonates, the disease is usually manifested as sepsis or meningoencephalitis. In pregnant women, symptoms may be milder; bacteremia is manifested clinically as an acute febrile illness, and meningoencephalitis is rare. Illness usually occurs in the third trimester, probably related to the major decline in cell-mediated immunity seen at 26 to 30 weeks of gestation. Twenty-two percent of perinatal infections result in stillbirth or neonatal death; premature labor is common (3). Unrelated to pregnancy, gastrointestinal illness with and without fever also occurs, but more so in outbreak settings. Diagnosis is confirmed by isolation of the bacterium from CSF, blood, amniotic fluid, placenta, meconium, lochia or other sites of infection.

Georgia Department of Human Resources
Division of Public Health Epidemiology Branch
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
The Georgia Epidemiology Report is a publication of the Epidemiology Branch,
Division of Public Health, Georgia Department of Human Resources

Outbreaks
Outbreaks of listeriosis have been publicized recently (4,5,6). In 1998, the United States experienced one of its largest outbreaks of listeriosis, affecting 101 people in 22 different states. The outbreak was linked to hot dogs and deli meats. Georgia was not involved in the most recent outbreak, which occurred in 8 states in summer to fall of 2002, and included at least 46 cases, including 7 deaths and 3 fetal losses. This outbreak was probably linked to a plant that processed ready-to-eat turkey and chicken, and prompted a product recall. An outbreak of listeriosis in 2000, in North Carolina, involved 12 cases, 10 of whom were pregnant and had adverse outcomes for their fetuses/babies. This outbreak occurred among Hispanics, and was linked to illegally sold queso fresco. There have also been outbreaks of gastroenteritis linked to foods such as corn (7).
Surveillance
Likely due to its high mortality, listeriosis is reported at a higher rate to public health authorities more often than other food-borne bacterial infections. These reports, however, comprise only a fraction of the actual number of cases that occur (8). Rates of infection have decreased in Georgia and this is consistent with national trends (figures 1 and 2). This is partially due to the actions of government regulatory agencies. Since 1989, the Food and Drug Administration (FDA) has maintained a "zero-tolerance" policy for L. monocytogenes in ready-to-eat foods. As a result, annual incidences have declined. There have been multiple recalls. In 2002, in Georgia there was a major recall involving queso fresco. Out of the estimated 2,500 cases that occur yearly in the U.S., only 373 are obtained by passive surveillance and 1,259 by active surveillance (8). In Georgia, since 1996, laboratory-based active surveillance is done in all counties through the FoodNet project. The ability of this organism to cause severe disease and outbreaks, the fact that it is under-reported, and the goal of Healthy People 2010 to further decrease the numbers of listeria cases in our country by 50%, led us to improve our surveillance system in Georgia.

New Reporting System
Until recently, listeria infection was not considered to be a notifiable disease in the United States. In Georgia, only invasive listeriosis (Listeria monocytogenes isolated from normally sterile sites) has been reportable. In 1999, the CDC expanded its case definition to include listeriosis diagnosed by isolation from non-sterile sites. We are now changing our case definition so that a listeriosis case will be defined as a person from whom L. monocytogenes is isolated from blood, cerebrospinal fluid, or other normally sterile sites, or from placenta or products of conception in conjunction with fetal death or newborn illness.

planning to work with professional societies and sentinel sites with high-risk patient populations to increase awareness about listeriosis. Goals include getting physicians to do appropriate diagnostic workups on high-risk patients, and educating them regarding high-risk populations and behaviors so they can focus their patient education. By achieving these goals, we will increase reporting while further decreasing rates of disease.
This article was written by Melissa Tobin-D'Angelo, M.D., Heather Kotler, M.P.H., and Sandra Chaves, M.D., M.Sc.

There are multiple reasons for expanding the reporting definition. One large series of listeria cases described a neonatal mortality rate of 50% (9). An estimated incidence of listeriosis in the general population is .7/100,000 (10). This is much higher in pregnant women (12/100,000) and infants (10/ 100,000) (11). Listeriosis is difficult to clinically diagnose in pregnant women because they often have mild illnesses. A fever and influenza-like symptoms are the most commonly reported symptoms, and 13-45% of mothers are asymptomatic (12). Many of these patients are not ill enough to require a blood culture, which is the primary means of diagnosing invasive listeriosis. Other means of diagnosing pregnancy-related infections include placental cultures, amniotic fluid cultures, and pathological examination of placental tissue.
Next steps
A focus group study done by Research Triangle Institute on patients from a number of states and varying levels of education found that only 8 of 63 pregnant women received information about food safety from their physicians (13). Of the women studied, 27% regularly ate soft cheeses while pregnant, and 98% ate cold deli meat. Most of these women wanted education about food safety from their physicians. These findings help confirm that physicians and patients need further education about listeriosis and its prevention. The Georgia Department of Human Resources, Division of Public Health is

References:
1. www.cdc.gov/foodnet/ 2. Pinner RW, Schuchat A, Swaminathan B et al. Role of foods in
sporadic listeriosis. JAMA 1992;267:2046-2050. 3. Mandell GL, Bennett JE, Dolin R. Mandell, Douglas, and Bennett's
Principles & Practice of Infectious Diseases 5th ed. Philadelphia, 2002. 4. MMWR 2002;51:950-951 5. MMWR 2001;50:560-562 6. MMWR 2000;49:1129-30. 7. Aureli P, Fiorucci GC, Caroli D et al. An outbreak of febrile gastroen-
teritis associated with corn contaminated by Listeria monocytogenes. New Engl J Med 2000;342:1236-41. 8. Mead PS, Slutsker L, Dietz V, et al. Food-related illness and death in the United States. Emerging Infectious Diseases 1999;5:607-625. 9. Siegman-Igra Y et al. Listeria monocytogenes infection in Israel and review of cases worldwide. Emerging Infectious Diseases 2002;8:305-310. 10. Silver HM. Listeriosis during pregnancy. Obstetrical and Gynecological Survey 1998;53:737-740. 11. Schlech WF III. Foodborne Listeriosis. Clin Inf Dis 2000;31:770-5. 12. McLauchlin J. Human listeriosis in Britain, 1967-85, a summary of 722 cases. Epidemiol Infect 1990;104:181-189. 13. www.fsis.usda.gov/oa/research/lmfocus.htm

Figure 1. Relative rates compared with 1996 of laboratory-diagnosed cases of Campylobacter, Listeria, and Yersinia, by year -- Foodborne Diseases Active Surveillance Network, United States, 1996-2002

Figure 2. Rates of L. monocytogenes infection per 100,000 population, Georgia 1994-2002*

caes/100,000

0.6 0.4 0.2
0 94 95 96 97 98 99 00 01 02 year

-2 -

Reporting Outbreaks in Georgia

Any cluster of illness should be immediately reported to public health authorities. A cluster of illness is defined as two or more cases of a similar disease (with either a laboratory confirmed diagnosis or a similar clinical syndrome) that share common geographic and time characteristics. A cluster of illness that is related to a common source is considered an outbreak. A cluster may represent a localized outbreak or may be one of many clusters representing a multi-state or multi-country outbreak. When small clusters of illness are dismissed as unimportant, large outbreaks may be overlooked.
Clusters and outbreaks of illness come to the attention of public health authorities in a variety of ways. Some outbreaks (particularly foodborne illness outbreaks) are reported by individuals who are ill. Outbreaks may also be detected through routine disease surveillance. However, one of the most important means of outbreak detection is reporting by clinicians. In many cases, it is an astute clinician who is the first to recognize a disease outbreak. Acquired immunodeficiency syndrome (AIDS), hantavirus pulmonary syndrome, and most recently severe acute respiratory syndrome (SARS), were first identified and reported to public health authorities by clinicians who recognized an unusual cluster of patients with similar symptoms.
When a cluster of illness is reported to public health authorities, immediate action should be taken to determine if the cluster may represent an outbreak, and to conduct an epidemiologic and environmental investigation to establish the cause of the illness and the source of exposure. Investigating an outbreak is important to identify and implement prevention and control measures that can eliminate the source of exposure. These measures may range from conducting restaurant inspections, product trace backs, or recalls in the case of a foodborne disease outbreak, to the implementation of new guidelines for case management or quarantine of exposed individuals.
Prompt reporting and investigation of outbreaks is critical. When reporting is delayed or incomplete laboratory investigation is done, it is often difficult, and sometimes impossible, to determine the etiology of an outbreak. For example, in suspected foodborne outbreaks, food samples are often discarded before laboratory tests can be conducted. In addition, delays in outbreak recognition impair our ability to detect etiologic agents in clinical specimens since the shedding period may have passed and individuals affected by the outbreak may have limited recall of their food history. Most importantly, delayed reporting can result in a lost opportunity to prevent additional cases of illness.

has the number of outbreaks that are reported. In 1995, eight outbreaks were reported to the GDPH. In 2002 this number increased to 65. In addition, since 2001, the GDPH has participated in the national EHS-Net Food Safety Project. EHS-Net is a network of environmental health specialists from the Centers for Disease Control and Prevention, the U. S. Food and Drug Administration, and 8 states. The main goals of the project are to identify environmental antecedents of foodborne illness and outbreaks and identify and offer training opportunities for future environmental health specialists. Through this project, GDPH has strengthened its relationship with local environmental health staff leading to improved reporting and investigation of foodborne outbreaks.
Current methods to detect outbreaks are improving. For example, two new tools that enhance detection of foodborne disease outbreaks at the national level are the Salmonella Outbreak Detection Algorithm (SODA) and PulseNet. SODA applies a statistical algorithm to data reported through CDC's National Salmonella Surveillance System to identify significant increases over a historical baseline for any given Salmonella serotype. This system, now employed at state health departments, including GDPH, can be used to help identify clusters and/or outbreaks. PulseNet is a national network of public health laboratories, including the Georgia Public Health Laboratory, that perform pulsed-field gel electrophoresis (PFGE) on bacterial isolates that might be foodborne. The network permits rapid comparison of PFGE patterns through an electronic database at CDC. Closely related PFGE patterns suggest a common source. PulseNet is helpful in epidemiologic investigations, particularly those that involve many states. In 2002, PulseNet identified an increase in cases of a specific strain of Salmonella Newport. The cases occurred in several states and other than their matching PFGE patterns, they did not seem to be related. Further investigation identified eating tomatoes as a risk factor for illness. A total of 297 cases in 21 states were identified. A product traceback identified a single tomato packinghouse as the common source of the tomatoes. Efforts to identify and eliminate the source of contamination in the packinghouse are ongoing.
Clinicians should remember that any cluster of illness is reportable, even if there is no laboratory confirmation of etiology. This includes (but is certainly not limited to) clusters of clinical syndromes such as upper respiratory tract infection in school children, gastrointestinal illness in nursing home residents, or suspected foodborne illness among attendees at a wedding reception. In 2002, less than 25 percent of reported outbreaks were caused by etiologic agents that are considered reportable by law.

Investigating outbreaks is also a critical means of identifying novel and emerging pathogens as well as maintaining awareness of ongoing problems. The findings of an investigation provide the basis for regulatory and other changes to improve community safety. At the regional and national levels, surveillance data provide an indication of the etiologic agents, vehicles of transmission, and contributing factors associated with disease outbreaks and help direct public health actions to reduce illness and death in the population.

Clusters of illness should be reported immediately to the County Health Department or District Health Office where the cluster occurred. Clusters may also be reported by calling 1-866-PUB-HLTH. The report should include as much information as possible including: the place where the outbreak occurred, the suspected etiology and source of exposure, common symptoms of those who are ill, incubation period (if known), severity and duration of illness, and contact information for ill persons, and the place of exposure.

In Georgia, the capacity to identify and investigate disease outbreaks has increased dramatically. Since 1995, the number of infectious disease epidemiologists at the Georgia Department of Human Resources, Division of Public Health (GDPH) has increased from less than 5 to more than 20 and each of Georgia's 19 Health Districts now has a full-time District Epidemiologist. As this capacity to investigate outbreaks has increased, so

For more information about reporting disease clusters, contact the Notifiable Disease Section (Cindy Burnett) at 404-657-2588.
Article written by Cindy Burnett, Sandra Chaves, M.D., M.Sc., and Cherie Drenzek, D.V.M., M.S.

-3 -

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

July 2003

Volume 19 Number 07

Reported Cases of Selected Notifiable Diseases in Georgia Profile* for April 2003

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 April 2003
2003 20
2205 4 1 30
991 1 27 11 4 0 1 0 1 0 33 38 3 13 20 14 0 26

Previous 3 Months Total

Ending in April

2001

2002

2003

141

124

72

7665

8547

7592

27

27

21

4

7

4

210

183

128

4049

4327

3604

31

21

10

197

147

76

87

106

54

2

4

6

0

1

2

20

10

8

5

2

0

7

6

1

0

0

0

183

224

146

68

262

210

21

25

16

78

75

67

169

172

113

248

216

119

5

7

0

130

122

91

Previous 12 Months Total

Ending in Arpil

2001

2002

2003

631

625

617

31880

33804

34077

173

159

112

44

51

42

1140

915

880

19896

18795

18028

94

98

67

545

868

419

401

437

421

10

13

23

0

2

4

55

42

31

7

4

0

38

23

25

1

0

0

1672

1739

1873

326

1026

1835

112

103

98

283

297

334

565

690

634

819

820

640

21

24

7

677

542

516

* 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.

Report Period
Latest 12 Months: 06/02-05/03 Five Years Ago: 06/98-05/99 Cumulative: 07/81-05/03

Total Cases Reported* <13yrs >=13yrs Total

0

1,120 1,120

12

1,493 1,505

211

26,146 26,357

Percent Female

AIDS Profile Update
Risk Group Distribution (%) MSM IDU MSM&IDU HS Blood Unknown

24.9

31.9

8.1

1.8

11.2

1.4

45.6

23.1

37.3

15.8

4.3

18.6

1.6

22.4

17.9

47.3

17.1

5.3

13.6

1.9

14.8

Race Distribution (%) White Black Other

18.2 76.3

5.4

21.6 76.3

2.1

33.5 64.0

2.5

MSM - Men having sex with men

IDU - Injection drug users

HS - Heterosexual

* Case totals are accumulated by date of report to the Epidemiology Section

- 4 -