Georgia epidemiology report, Vol. 14, no. 7 (July 1998)

July 1998

volume 14 number 7

Division of Public Health
http://www.ph.dhr.state.ga.us Director
Kathleen E. Toomey, M.D., M.P.H.
Epidemiology and Prevention Branch State Epidemiologist
Acting Director Kathleen E. Toomey, M.D., M.P.H.
Epidemiology Section
Chief Paul A. Blake, M.D., M.P.H.

The Georgia Epidemiology Report is a publication of the Epidemiology Section of the Epidemiology and Prevention Branch, Division of Public Health, Georgia Department of Human Resources
Outbreak of Escherichia coli O157:H7 infections associated with a water park
Introduction:
On June 19, 1998, the Georgia Division of Public Health was contacted by a Bartow County woman who reported a case of hemolytic uremic syndrome (HUS) (usually caused by E. coli O157) and several cases of diarrheal illness among children she had supervised in group activities. Health officials from the Rome Health District were alerted and immediately investigated the childrens illness histories, their activities and the foods that they had eaten. One of the groups activities had been visiting Water Park A. That afternoon, a local hospital reported a laboratory-confirmed case of E. coli O157 infection to the Cobb County Board of Health in a child who was not part of the Bartow County group. Cobb County public health officials determined that this child, a vegetarian, had also visited Water Park A. Over the next few days, several more cases were detected and investigated.

Public Health Advisor Mel Ralston
Notifiable Diseases
Jeffrey D. Berschling, M.P.H., Katherine Gibbs McCombs, M.P.H., Carol Hoban, M.S., M.P.H., Jane E.
Koehler, D.V.M., M.P.H., Laura Gilbert, M.P.H. Amanda Reichert, R.N., M.S.
Chronic Disease and Injury
Ken Powell, M.D., M.P.H.- Program Manager, , Patricia M. Fox, M.P.H., Rana Bayakly, M.P.H., Mary P. Mathis, Ph.D., M.P.H., Alexander K. Rowe, M.D., M.P.H.
Linda M. Martin, M.S.
Tuberculosis
Rose Marie Sales, M.D., M.P.H.- Program Manager Naomi Bock, M.D., M.S., Beverly DeVoe, M.S.
HIV/AIDS/Sexually Transmitted Diseases
John F. Beltrami, M.D., M.P.H.&T.M.- Program Manager Andrew Margolis, M.P.H., Lyle McCormick, M.P.H. Ann Buckley, M.P.H., Amy Hephner, M.P.H. Laura Axelson, M.P.H.

Methods:
Suspected and laboratory-confirmed E. coli O157 infections were reported to State and local health authorities by parents, hospital infection control personnel, physicians, and laboratories. Persons who had experienced a diarrheal illness within ten days after visiting Water Park A, and any persons with bloody diarrhea in June, 1998, were asked to submit a stool specimen to the Georgia Public Health Laboratory for culture for E. coli O157. All available E. coli O157:H7 strains were tested by pulsedfield gel electrophoresis (PFGE), a method for genetic subtyping which can determine whether tested strains are indistinguishable.
District and State investigators interviewed infected persons or their parents or guardians to obtain detailed demographic information and histories of illness, food and drink consumption, travel, and exposures to swimming pools. The data were entered into an EpiInfo database at the State. Cases were defined as culture-confirmed E. coli O157:H7 infections in persons who had lived in or visited Georgia during June.
Environmentalists inspected Water Park A repeatedly beginning June 20.
Results:
We identified 35 culture-confirmed cases of E. coli O157:H7 infection in persons with Georgia exposures during June. Twenty-six of these occurred in persons with a history of visiting Water Park A during the 10 days before onset of illness. The E. coli Ol57:H7 strains from 19 of the 26 park visitors and all 9 of the non-visitors were available for PFGE. All 19 who had visited Water Park A had a single unusual PFGE pattern, while the 9 who had not visited the park had other patterns (p<0.0001) (Fisher 2-tailed exact test).

Perinatal Epidemiology
James W. Buehler, M.D. - Program Manager Leslie E. Lipscomb, M.P.H.
Cheryl Silberman, Ph.D., M.P.H. Hui Zhang, M.D., M.P.H.
Mohamed Qayad, M.D., M.P.H.
Preventive Medicine Residents
Mark E. Anderson, M.D., M.P.H. & Anthony Fiore, M.D., M.P.H.

The ages of the 26 park visitors with confirmed cases ranged from 11 months to 12 years (median age of 4 years); half were female. Seventeen (65%) were from counties in Northwest Georgia and 9 were from other states (2 AL, 1 AZ, 1 FL, 1 IL, 1 KY, 2 TN, 1 TX). All 26 (100%) had diarrhea, 23/24 (96%) had abdominal cramps, 18/23 (69%) had bloody diarrhea, and 14/23 (61%) reported subjective fever. Seven (27%) of the 26 park visitors with confirmed cases developed HUS, and one of these died.
The dates when transmission occurred at Water Park A were determined by examining the dates on which the infected children had visited the park. Twenty-one (81%) of the 26 children visited the park on only one day during the period June 10-22. The days of single exposures occurred on June 11 (12 children), 12 (1), 17 (6), and 18 (2).

EIS Officers
Julia Samuelson, R.N., M.P.H., & Keoki Williams, M.D.
Graphics Dept.
Jimmy Clanton Jr. & Christopher Devoe
Georgia Epidemiology Report Editorial Board
Editorial Executive Committee
Andrew Margolis, M.P.H. - Editor Paul A. Blake, M.D., M.P.H.
Jane E. Koehler, D.V.M., M.P.H. Jeffrey D. Berschling, M.P.H.
Kathleen E. Toomey, M.D., M.P.H. Angela Alexander - Mailing List Christopher Devoe - Graphics

Most of the infected children played in both of 2 adjacent children's pools. However, all 21 children with single day exposures played in Pool 1. Parents and guardians were uncertain about whether or not 3 children had played in Pool 2. Of the remaining 18 children, 3 (17%) had not played in Pool 2.
On June 20, environmentalists found that chlorine levels in Pool 1 were below the 1.0 ppm minimum requirement for Cobb County. This pool was temporarily closed. On June 29, a State environmentalist learned from park maintenance personnel that the chlorine controller would at times shut down automatically after 2 hours of continual maximal electronic requests for additional chlorine.
Discussion:
The results of the investigation are consistent with transmission of E. coli O157:H7 infection in Pool 1 at Water Park A on June 11, 12, 17, and 18. It is likely that there was contamination of Pool 1 on June
Georgia Department of Human Resources Division of Public Health Epidemiology & Prevention Branch, Epidemiology Section Two Peachtree St., N.W., Atlanta, GA 30303 - 3186 Phone: (404) 657-2588 Fax: (404) 657-2586

11 by feces from a child with an E. coli O157:H7 infection. The smaller number infected on June 12 could have resulted from a new contamination or from persistence of the organisms overnight. The 4 day interval between June 12 and 17 without new infections, followed by infection of a substantial number of cases on June 17, suggests that there was a new contamination of the pool on June 17. Again, the smaller number on June 18 could have resulted from new contamination or from persistence. Since many children go to the park repeatedly during the summer, and most E. coli O157 infections are never cultured and diagnosed, it is highly possible that one or more children were infected on June 11 or 12 at the park, became ill several days later, and contaminated the pool on June 17 and/or 18.
Several factors could have contributed to chlorine depletion in Pool 1: 1. Pool 1 has a large surface area and contains 40,000 gallons of water. 2. Pool 1 uses unstabilized chlorine. Sunlight (UV) breaks down unstabilized chlorine quickly. Some estimates suggest that chlorine levels are halved in 15-30 minutes of direct sunlight. 3. Children frequently add organic loads, such as urine, to a pool and thus deplete free available chlorine. 4. Aeration caused by waterfalls, slides, and childrens splashing consumes free available chlorine.
With all of these factors operating, there may have been virtually no free chlorine available within minutes after chlorinated water entered Pool 1. Chlorine levels in water entering the pool had been set at a level of 1.5 ppm, but to maintain 1.5 ppm in the water leaving the pool, the controller would have to be set at or above 3 ppm on days with direct sunlight; the precise amount would have to be determined by testing.
When there is fecal contamination of pool water, persons in the immediate vicinity are at risk even if there is proper chlorination, since it takes time for chlorine to kill bacteria, and the organic matter surrounding the bacteria partially protect them from chlorine. However, chlorine will eventually kill the bacteria. Thus, maintaining optimal chlorine levels should reduce the risk of transmission of E. coli O157 bacteria via swimming pool water after fecal contamination. Due to the dangers posed by fecal contamination, children with diarrhea or with unprotected diapers should not be allowed in swimming pools. In addition, diapers should be changed in designated areas only.
The problems identified in this investigation are not unique to Water Park A; all water parks and pools share the challenge of minimizing the risk of transmission of infectious diseases when many bodies are bathed by the same water. Since swimming pools and other recreational bathing facilities have been identified as vehicles of transmission for numerous pathogens, and there is no simple solution, federal and state agencies and the recreational water industry should work to make these facilities as safe as possible. The State of Georgia is developing new guidelines for recreational bathing facilities.
Although recognized E. coli O157 infections are not common in Georgia (39 in 1996, 46 in 1997), their significance to the patient and to public health makes identifying the infection important. One of the problems faced in this investigation was that many people with suspected infections did not have stool cultures performed, or had stool cultures performed that did not include the special medium needed to identify E. coli O157. Bloody stools are much more likely than non-bloody stools to be culture-positive for E. coli O157. We encourage clinicians to culture persons with bloody diarrhea specifically for E. coli O157 so that the appropriate culture medium will be used.
Written by: Laura Gilbert, M.P.H. and Paul Blake, M.D., M.P.H.

5
4
3
2
1
0 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
E. coli O157:H7 infections among persons who visited Water Park A in June 1998, by date of onset of illness
Georgia Division of Public Health E.coli 0157: H7 Investigating Team
Epidemiology and Prevention Branch Kathleen Toomey, M.D., M.P.H. Paul Blake, M.D., M.P.H. Scott Kellerman, M.D., M.P.H. Jane Koehler, D.V.M., M.P.H. Katherine McCombs, M.P.H. Laura Gilbert, M.P.H. Preeti Pathela, M.P.H.

Georgia Public Health Laboratory Elizabeth Franko, Dr.P.H. Mahin Park, Ph.D. Marsha Ray, M.S., S.M. (AAM) Leith Cobb M.S., M.T. (ASCP) Robert Manning Jr. , B.S. James Benson, B.S., M.T. (ASCP)
Martha Bates

Environmental Health and Injury Prevention Branch
Tom Bennett, B.S. (REHS)

Health District 3, Unit 1
Virginia Galvin, M.D., M.P.H. Barbara Kauffman, B.S.N., R.N. Joy Wells, M.P.H. Pat Koffman, B.S. Tammy Hamilton, B.S. Murl McCall, B.S.

Health District 1, Unit 3 Joy Benson, M.D. Joan Mulkey, R.N.

Health District 1, Unit 1 C. Wade Sellers, M.D., M.P.H. Debbie Abercrombie, B.A. Scott Henson, B.S.

Health District 10 Barbara Rivers, R.N., M.Ed.,N.P. Lynn Beckmann, R.N., D.V.M. Scott Uhlich, B.S., M.E.P.

Health District 3, Unit 4 Ronnie Hinton, B.S.

CDC, National Center for Infectious Diseases Tim Barrett, Ph.D.

A Laboratorians Look into E. coli O157:H7
Laboratory Tests
The bacterium E. coli O157 does not ferment sorbitol, as do most other strains of E. coli. The Georgia Public Health Laboratory (GPHL) typically first cultures stool samples on a MacConkey medium that contains sorbitol as the carbohydrate source. The isolates are then tested by biochemical and serologic assays. The serologic tests determine whether the E. coli is serotype O157. The presence of the H7 antigen is determined next by performing a motility test and H7 serotyping. Isolates are also tested for the presence of Shiga-Like Toxins (SLT). All O157 isolates are characterized by pulsed-field gel electrophoresis (PFGE).
What Is Pulsed-Field Gel Electrophoresis?
Epidemiologic investigations of disease outbreaks traditionally have been based on phenotypic and metabolic differences between sub-types of the same strain. These differences have been determined by serotyping, antimicrobial-susceptibility testing, and bacteriophage typing. As a result of advances in technology, however, laboratorians are now equipped to determine very precise sub-types within a strain through the use of DNA fingerprinting. These geneticfingerprinting techniques include polymerase chain reaction (PCR), ribotyping, and PFGE. GPHL used PFGE, in addition to routine laboratory methods, to support the epidemiologic investigations of the water park outbreak.
PFGE analysis of bacterial DNA is based on using restriction enzymes that cut DNA at specific cleavage points (referred to as restriction sites) that are specific
- 2 -

for each enzyme. As a result, the application of different enzymes provides different-sized fragments. The fragments are next subjected to pulsed electrophoresis, which cyclically changes direction from side to side until all the fragments have been moved and arranged by size in the gel. The bigger fragments are less mobile and stay at the top; the smaller ones move to the bottom of the gel. The resulting fingerprint, which consists of a number of bands resembling a bar code, becomes visible on the gel after it is stained with a fluorescent dye and exposed to an ultraviolet light source.
The advantage of PFGE over other molecular techniques is its ability to separate DNA into a smaller number of fragments (e.g., 1030 bands), making comparative analysis easier. The number and position of separated fragments can be analyzed by computer for better resolution. When patterns from different patients are compared, the presence of additional bands, the deletion of a band, or differences in the position of the bands (i.e., an upward or downward shift) indicate that the organisms differ from each other. The isolates that demonstrate the same pattern are likely to be related, especially if the epidemiologic data support the laboratory findings.
The PFGE analysis included subjecting all isolates of E. coli O157:H7 to the restriction enzyme XbaI. All E. coli O157:H7 isolates associated with the water park outbreak, along with isolates from a sample of ground beef in May, demonstrated the same XbaI pattern. To further investigate these findings, the Georgia Public Health Laboratory used two additional restriction enzymes, SpeI and BlnI. The fingerprint patterns obtained by using these enzymes were all indistinguishable for isolates from persons who visited the water park and for the ground beef isolates (Figure 1). However, they differed from other isolates tested by the Georgia Public Health laboratory.
Conclusion
E. coli O157:H7 is truly an emerging pathogen in Georgia, with infections being recognized and reported more and more commonly. During the last 5 years (1993-1997), the number of these infections reported each year has risen steadily from 15 to 46, and in just the first eight months of 1998 more cases (50) were reported than in any previous year.
The investigation of the water park outbreak demonstrates the critical importance of genetic fingerprinting of E. coli O157:H7 strains by PFGE in epidemiologic investigation of these strains. PFGE is now available at the GPHL, and we encourage laboratories and clinicians to submit E. coli O157:H7 strains and appropriate specimens to the GPHL for testing.
Contributor
This article was contributed by Mahin M. Park, Ph.D., Clinical Laboratory Service Supervisor, Georgia Public Health Laboratory
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

(Escherichia coli O157:H7)
(MMWR) Morbidity and Mortality Weekly Reports
YYoouu M Maayy HHaavvee M Miisssseedd
July 31, 1998 / Vol. 47 / No. RR-12
HIV Prevention Through Early Detection and Treatment of Other Sexually Transmitted Diseases -- United States. Recommendations of the Advisory Committee for HIV and STD Prevention.
July 24, 1998 / Vol. 47 / No. RR-11
Advances in Global Measles Control and Elimination: Summary of the 1997 International Meeting.
July 10, 1998 / Vol. 47 / No. RR-10
Compendium of Measures to Control Chlamydia psittaci Infection Among Humans (Psittacosis) and Pet Birds (Avian Chlamydiosis), 1998
July 3, 1998 / Vol. 47 / No. SS-2
Tetanus Surveillance -- United States, 1995-1997 Postneonatal Mortality Surveillance -- United States, 1980-1994 Abortion Surveillance -- United States, 1995
The Morbidity and Mortality Weekly Report (MMWR) series is produced by the Centers for Disease Control and Prevention (CDC). Publications are available on the World-Wide Web at http://www.cdc.gov or by calling 202.512.1800 for paper copy.

(Figure 1) PulsedField Gel Electrophoresis Patterns of E. coli O157:H7 Isolates

"OUTBREAKS and CLUSTERS"

Outbreak: The occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time.

Lanes 1,5,7,11,15-Controls Lanes 2,4-Water park case-isolates (XbaI) Lane 3-Ground beef isolate(XbaI) Lanes 8,10-Water park case-isolates (SpeI) Lane 9-Ground beef isolate (SpeI) Lanes 12,14-Water park case-isolates, (BlnI) Lane 13-Ground beef isolate, (BlnI) Lane 6-An isolate unrelated to the water park cases with indistinguishable XbaI and SpeI patterns but no match when subjected to BlnI restriction enzyme (results not shown).

Cluster: An aggregation of cases in a given area over a particular period without regard to whether the number of cases is more than expected.
CDC. Principles of Epidemiology: An Introduction to Applied Epidemiology and Biostatistics. 2nd ed. Atlanta, U.S. Department of Health and Human Services, Public Health Service, 1992.

- 3 -

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

July 1998

Volume 14 Number 7

Reported Cases of Selected Notifiable Diseases in Georgia Profile* for April 1998

Selected Notifiable Diseases Campylobacteriosis Chlamydia genital infection 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 1998
1998 55 1944 9 0 76 1560 3 77 17 0 2 6 1 3 0 87 97 12 28 62 82 0 44

Previous 3 Months Total

Ending in April

1996

1997

1998

152

116

129

3300

3928

6689

13

6

22

6

8

0

149

180

214

4829

4567

5093

15

11

11

88

134

173

6

48

66

2

2

0

0

0

3

52

38

31

1

6

1

7

6

5

0

0

0

203

220

202

147

236

244

53

40

35

131

107

67

353

318

222

263

361

229

10

9

2

203

193

140

Previous 12 Months Total

Ending in April

1996

1997

1998

978

742

796

12200

14162

19520

119

84

93

34

50

30

616

878

945

21427

19210

19104

35

47

45

138

475

829

44

109

263

10

3

4

8

2

12

133

125

108

9

15

4

31

35

14

0

0

0

1703

1463

1360

1028

1247

1213

284

183

146

616

457

309

1531

1305

977

1136

1197

1033

62

27

16

801

765

616

* 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: 08/97 to 07/98 Five Years Ago: 08/92 to 07/93 Cumulative:
07/81 to 07/98

Total Cases Reported *
1362 1920 19380

AIDS Profile Update

Percent Female

Risk Group Distribution (%)

MSM IDU MSM&IDU

HS Blood

Unknown

18.4

40.8

17.2

4.2

15.3

1.0

21.4

13.9

48.8

20.9

6.4

11.8

1.9

10.1

15.0

51.2

19.2

5.8

11.9

2.0

9.8

Race Distribution (%) White Black Other

23.6 73.7

2.6

36.4 61.6

2.0

38.8 59.1

2.0

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-