Friday, February 6, 2004

This Week in the News

Foege WH et al.
International Journal of Epidemiology
1976; 5:29-37

Epi Update Managing Staff:


John Agwunobi, MD, MBA, Secretary,  Department of  Health 

Landis Crockett, MD, MPH, Director, Division of Disease Control 

Don Ward, 
Acting Bureau Chief, 
Epi Update Managing Editor 

Jaime Forth, Copy Editor/ Writer 

A R T I C L E S

Back to top
 

 
Background
During May and July, 2003 the Polk County Health Department was informed of two separate clusters of gastrointestinal illness associated with events at local lakes. The May cluster consisted of forty people attending a preschool end-of-year celebration. The party was held at a private camp that had lakeside recreational facilities. Symptoms described were nausea, vomiting and diarrhea. The July cluster involved thirty people at a birthday picnic at a different local public access lake. Diarrhea, abdominal cramps, nausea vomiting, malaise and fever were the initial symptoms reported. 

Methods
The Polk County Health Department epidemiology team investigated both clusters. Standardized questionnaires were administered to both cohorts via telephone. Lake water samples were collected and analyzed for indicator organisms. Neither food nor clinical samples were available in either cohort. Statistical analysis was performed using EpiInfo 2002 software. 

Results
May Cohort: A total of 34 people who attended and four who did not attend the May event were interviewed. Three of the four who did not attend were determined to be parents of children that had attended. One parent was a secondary case. The ages of this cohort ranged from 4-63 years (mean=19.7 yrs, median=5 yrs, and mode=5 yrs). Twenty-two (57.9%) of the thirty-eight people interviewed became ill, and one out of the twenty-two sought medical treatment. A total of 16 of the 22 ill persons were children. Analysis of illness onsets of this cohort revealed two children with illness prior to the event. The primary case onsets occurred May 13 through May 15; secondary onsets occurred on May 16. (See Chart 1). The incubation period ranged from 17 to 81 hours with a median of 35 hours. The predominant symptoms were vomiting (96%), nausea (68%), abdominal cramps (59%), and diarrhea (54%). Seventy-one percent (71%) of those reporting vomiting were under the age of five.  (See Chart1)   

Swimming (RR=4.36, CI 1.20-15.86, p=0.002) and water slide use (RR=2.55, CI 1.16-5.61, p=0.009) exposures were statistically associated with illness. Water laboratory analysis results were within satisfactory limits for both the bathing facility and the potable water supply (i.e. less than 200 fecal coliforms per 100 ml of water).   

July Cohort:  A total of 29 people out of 30 from this cohort were interviewed (96.7%). Ages ranged from 4-54 years with a mean of 25.4 years, a median of 27 years and a mode of 8 years. Ten (34.5%) of the 29 became ill after the picnic, and none of the ill sought medical treatment. Of the 10 ill, 6 were children. Incubation periods ranged from 8 to 48 hours with a median of 23.5 hours. Diarrhea (90%), vomiting (80%), abdominal cramps (70%), fever (40%), malaise (30%), headache (30%), and body aches (30%) were the reported symptoms. All of the children reported vomiting, but only 50% of adults did. Onsets of illness were July 21 and 22, 2003. (See Chart 2).

Analysis of the food items did not reveal any significant relative risks. Tubing (RR=9.64, CI 1.39-66.66, p= 0.002) and wakeboarding (RR=7.33, CI=2.562-20.99, p=0.0007) were statistically associated with illness. Investigation into whether or not a sewer break occurred in vicinity was negative. Three lake water samples taken at various points near the shore were within established fecal coliform limits.

Discussion
These two outbreaks of gastrointestinal illness are statistically linked to exposure to lake water. Food exposures were not implicated in either outbreak. Both cohorts had illness onset dates that were clustered, indicating a common point source for each. The two outbreaks occurred in different bodies of water, two months apart and do not appear to be epidemiologically connected. The May cohort appears to have two index cases that may have been the source of the organism, while the July cohort source was not determined. Both bodies of water had currently acceptable indicator organism levels. While clinical samples were not available to analyze for pathogens, the incubation period and symptoms are suggestive of Norovirus.   

Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, nonenveloped viruses that cause acute gastroenteritis in humans. The incubation period for Norovirus-associated gastroenteritis in humans is usually between 24 and 48 hours (median in outbreaks 33 to 36 hours), but cases can occur within 12 hours of exposure. Norovirus infection usually presents as acute-onset vomiting, watery non-bloody diarrhea with abdominal cramps, and nausea. Low-grade fever also occasionally occurs, and vomiting is more common in children. Symptoms usually last 24 to 60 hours. Recovery is usually complete and there is no evidence of any serious long-term sequellae. Noroviruses are transmitted primarily through the fecal-oral route, either by consumption of fecally contaminated food or water or by direct or indirect person-to-person spread. Noroviruses are highly contagious, and it is thought that an inoculum of as few as 10 viral particles may be sufficient to infect an individual. 

Norovirus is a relatively stable virion in external environments. Much is still to be learned about its durability and survival in recreational bodies of water including lakes, ponds, interactive water fountains, water parks, spas and swimming pools. They are able to survive freezing, temperatures as high as 60°C, and have even been associated with illness after being steamed in shellfish. Moreover, noroviruses can survive chlorine contact up to 10 ppm chlorine. The spread of infection can typically be decreased by standard measures for control of diarrhea such as good infection control for densely populated facilities, proper personal hygiene (especially hand hygiene), cleanliness of surfaces, and exclusion of those ill if associated with care-giving or food service. However, in situations where mode of transmission is not person-to-person, interventions must then be based on the most likely exposure risk.

Although reports of waterborne transmission of viruses, particularly the Norovirus, are not as frequent as foodborne or person-to-person transmission, there have been a number of similar events reported. Detection of Norovirus in a water matrix is challenging, expensive and experimental. Only recent advances in laboratory detection methods have allowed the virus to be detected accurately in human specimens. It is very important that recreational and drinking water exposures be considered potential risk factors by epidemiologists during investigation of gastrointestinal illness clusters.

Back to top
 

The January 30^th bi-weekly conference call was attended by Bureau of Epidemiology staff and over 148 county health department personnel.  Highlights of the call are outlined here for those who were unable to participate. 

Disease Tracking in Merlin. Travis McLane explained that the Merlin reporting system is being modified to proactively track high priority diseases and notify users immediately when certain high threat diseases are entered into the system. These include smallpox, botulism, anthrax, plague, Q fever, tularemia, brucellosis, and hemorrhagic fever.  

Definitions have been set for case deletions on Merlin. From now on, unconfirmed high priority diseases, those ruled out by lab or clinical results, and diseases reported by counties prior to meeting the case definition may be deleted. When the deletions are made, the affected county will be notified. 

These and other modifications will be made to Merlin shortly and an e-mail will be sent to all users as soon as they’re completed.

EpiCom Changes. Pete Garner outlined changes to the EpiCom communications system coming soon. The most visible change will be the placement of the most recent forum posting to the top of each section.  The most active alerts will also be stationed at the top of the Forum page.  An attachment button will also be added so that if a user needs to provide documentation that goes beyond the scope of their posting, they’ll be able to add a document, spreadsheet or other file, subject to moderator approval. 

Other changes will be forthcoming and future comments and suggestions are always welcome. These changes are the result of previous input.  An announcement will accompany the changes when they’re completed.  

EIS Program. Julia Gill stated the history and purpose of the EIS Program, and stressed the importance of employing graduates of public health disciplines as investigators at our county health facilities. The deadline for applications is March 19^th and already over 100 graduate students have applied. The deadline for counties is March 12^th.  Interviews and orientation will be conducted on April 27-28^th and assignments will begin in late May or early June.

Influenza Surveillance Update. Angela Fix reported further decreases in the number of influenza cases statewide. She warned that the month of February normally shows an increase. According to the CDC, Reporting Week 3 shows the mortality rate is down. Delaware is the only state reporting widespread activity.  

She also advised that the avian flu poses no imminent threat to the U.S. 

Upcoming Training. Melanie Black reminded listeners of the regional training seminar scheduled for February 25-26^th. Registration is available online and only 10 slots remain.  On February 24^th a Grand Rounds will be presented on the topic, “ Norovirus Outbreak in a Private Elementary School in St. Lucie County, Florida.” 

Announcements. Don Ward summarized a recent smallpox reporting issue, which occurred earlier in the week in Putnam County. The case was finally diagnosed as chickenpox. The after-action report will be released soon.

The Pandemic Influenza Plan is being reviewed for changes. Treatment of high-risk populations, surveillance and a few other issues will likely be modified and forwarded to the counties for further review.

The next conference call is scheduled for Friday, February 13^th at 10:00 a.m. To be placed on the agenda, contact Melanie Black or Don Ward at 850.245.4444.

Back to top

During the past two months, Angela Fix has been visible as our spokesperson on influenza trends and events, but before she arrived in Tallahassee she resided in San Diego, California.

Angela received her BS in Medical Microbiology and Immunology from the University of Wisconsin in 1998. She spent the next three years at the University of Iowa, researching antimicrobial resistance, evaluating commercial testing systems, and performing statistical analyses on an international pathogenic bacterial surveillance project for a private laboratory. Her interest in epidemiology led her to the MPH program at San Diego State University where she obtained her graduate degree in 2003. Her thesis was on A Geospatial Analysis of Homicides in San Diego County, 1995-2001.

Angela's work at the Bureau of Epidemiology entails monitoring trends in infectious respiratory diseases, ensuring notifiable disease reporting accuracy within the electronic surveillance system, coordinating infectious disease surveillance and epidemiology programs within the bureau, and evaluating the program effectivess.

Prior to her decision to become involved in the science of disease control and investigation, Angela considered a role in seismology, with a career goal of being the first person capable of predicting earthquakes. Now that she maintains responsibility for surveillance and information of respiratory diseases, the state should be better prepared to address respiratory diseases.

Back to top
 

Title:
Norovirus Outbreak in a Private Elementary School in St. Lucie County, Florida, September 22-October 2, 2003. 

Presenters:
Edgar Morales, MPH, Environmental Epidemiologist, St. Lucie County Health Department
Karlette Peck, MPH, PA, Epidemiologist, St. Lucie County Health Department
Janet Wamnes, MS, Regional Environmental Epidemiologist, Bureau of Community Environmental Health  

Abstract:
On September 25, 2003, the St. Lucie County Health Department (SLCHD) was informed that teachers, staff and students from a private elementary school in St. Lucie County, Florida were ill with symptoms of a gastrointestinal illness. The same day the SLCHD sent a team of investigators to the school and began conducting an investigation. The school has a student body of  691, and  91 teachers and staff employees. The SLCHD conducted interviews to ascertain cases of ill individuals exhibiting symptoms of acute gastroenteritis. The reported symptoms among teachers, staff and students included vomiting, diarrhea, low-grade fever, nausea, abdominal cramps, fatigue and loss of appetite. No individuals had sought medical attention. The team decided to collect information about the meals and their ingredients served on September 23 and 24 after an assessment of some students’ onset time of illness, which was 24 to 48 hours.   

Personnel from the Epidemiology and Environmental Health Bureaus and the Bureau of Community Environmental Health conducted the investigation. The Environmental Health Division conducted a food service inspection. The Epidemiology Bureau investigators collected a menu list and developed a questionnaire that captured personal, demographic information and food consumption of students and staff who ate lunch at the school on September 23 and 24.  Recommendations were made to school officials to minimize person-to-person transmission of the virus including hand washing, using single serve utensils, a food education program for kitchen staff and closing the school for a day and a half. Norovirus was identified as the probable cause of the gastrointestinal illness. This outbreak is strongly associated with the consumption of the chef’s salad served on September 23.  

Additional Information:
The grand rounds presentation will begin promptly at 11:00 AM, EST on Tuesday, February 24, 2004. PowerPoint slides and the dial-in number will be available on the Bureau of Epidemiology intranet Website on Monday, February 23. CEUs will be provided for nursing and environmental health professionals.

Back to top
 

Medical Response to Nuclear and Radiological Terrorism
February 10, 2004
1:00 – 2:00 PM, EST 

Sponsored by the National Center for Environmental Health and the Public Health Training Network, this satellite broadcast will provide clinicians the most current information on possible radiological scenarios, basic information on protection, medical management of victims of a radiological incident and decontamination and treatment of victims. Visit the CDC/ATSDR Training and Continuing Education Online System at http://www.phppo.cdc.gov/phtnonline to register for this course. One hour of continuing education credit will be offered for various professions. Participants need to register and fill out an online evaluation for this program. Individuals who have questions about registration should call 1-800-41-TRAIN or email ce@cdc.gov. Questions regarding program content should be emailed to cdcresponse@ashastd.org. When emailing questions, please indicate Medical Response to Nuclear and Radiological Terrorism in the subject line. 

The Epidemiology and the Prevention of Vaccine-Preventable Diseases-Session 1
February 19, 2004
12:00 – 3:00 PM, EST  

This satellite broadcast, sponsored by the CDC Public Health Training Network and the National Immunization Program, is the first of a four part series on improving immunization practices in the United States. This series of satellite broadcasts is an annual offering. The target audience  is public and private healthcare providers including physicians, nurses, nurse practitioners, physician assistants, pharmacists and their colleagues who either give immunizations or set policy for their offices, clinics, communicable disease or infection control programs. At the end of this series, participants will be able to describe the difference between active and passive immunity, list two characteristics of live attenuated vaccines and list two characteristics of inactivated vaccines. For each vaccine preventable disease, the broadcast will discuss the disease including the causative agent, list high risk groups, identify those for whom routine immunization is recommended descried the characteristics of the vaccine used to prevent each disease, contraindications and/or adverse reactions and immunization schedule. 

Session One will cover principles of vaccination, general recommendations on immunization, and strategies to improve immunization coverage levels, including registries and vaccine coverage assessment. 

CEUs will be offered for various professions based on three hours of instruction. Participants need to register and fill out an online evaluation for this program. Individuals who have questions about registration should call 1-800-41-TRAIN or email ce@cdc.gov.  Site registration began on December 29, 2003. Individual registration began on January 22, 2004.

The Epidemiology and the Prevention of Vaccine-Preventable Diseases-Session 2
February 26, 2004
12:00 – 3:00 PM, EST 

This satellite broadcast is the second of a four-part series provided by the CDC Public Health Training Network on improving immunization practices in the United States. This broadcast will cover Pertussis, pneumococcal disease (childhood), polio, Hib and meningococcal disease. 

CEUs will be offered for various professions based on three hours of instruction. Participants need to register and fill out an online evaluation for this program. Individuals who have questions about registration should call 1-800-41-TRAIN or email ce@cdc.gov. 

Back to top
 

Over 40 cases of a possible norovirus were reported at a resort in Nassau County this week. For details, log onto EpiCom and click on the Food and Waterborne Disease Forum.

The Bureau of Epidemiology encourages Epi Update readers not only to register with the EpiCom system at https://www.epicomfl.net but to browse EpiCom and to contribute public health observations related to any suspicious or unusual situations or circumstances as appropriate.

Back to top

Weekly Update:  During the period January 25-31, the following arboviral activity (St. Louis encephalitis [SLE] virus, eastern equine encephalomyelitis [EEE] virus, West Nile [WN] virus and dengue virus) was recorded for Florida. 

Human:  No arboviral infections were confirmed in Florida residents this week. No counties are under medical alert. People are still encouraged to take precautions against mosquito bites, such as wearing mosquito repellent and eliminating stagnant water in birdbaths, ponds and other receptacles in which mosquitoes might breed.   

Sentinel Chickens:  This week, 656 samples were tested from 8 counties. There were 8 seroconversions to WN virus from Bay (1), Lee (1), Orange (1), Sarasota (1), Volusia (2), and Walton (2) counties. There was also one seroconversion to SLE virus from a chicken in Lee County.  So far this year, there have been 25 seroconversions to WN virus and two seroconversions to SLE virus.   

Bird Mortality:  No birds tested positive this week. One dead blue jay (collected on 1/14) from Miami-Dade County tested positive for WN virus. 

Equine* and other mammals:  One horse from Polk county (onset 1/9/) tested positive for WN virus. So far this year, two horses from Alachua (onset 1/9) and Clay (onset 1/6) counties have tested positive for EEE virus. 

Mosquito Pools:  Of 362 mosquito pools received so far this year from Escambia, Monroe, Palm Beach and Sarasota counties, all have tested negative for arbovirus. 

To date, 10 of Florida’s 67 counties have reported confirmed WN activity (birds, chickens and horses), 2 have reported EEE activity (horses) and two have reported SLE activity (chickens). 

Wild and Captive Birds**: For capture counts and historical data, go to http://www.pherec.org/DECS and click on “Arbovirus Ecology” to download the database, then the "Bird Serology" tab. 

See the web page for maps and summary information on 2003 activity: http://www.doh.state.fl.us/Environment/hsee/arbo/index.htm

Disclaimer: Please note that data is subject to change with confirmatory information. 

Back to Top
 

Bureau of Epidemiology

 Epi Update Archives

Florida Department of Health

My Florida

CDC