Foodborne Diseases Active Surveillance Network

[Kuester, Sarah]

Hello.  Below is today's MMWR article on the 1996 preliminary
results from the Foodborne Diseases Active Surveillance Network.
An electronic copy is available from CDC's World-Wide Web
server at http://www.cdc.gov.  (On the CDC Homepage, click on
MMWR, then select Weekly, then select Vol. 46 / No. 12.)   The
figure mentioned in the article will be visible on the Web site.

Thank you,
Sarah Kuester
Public Health Nutritionist
Centers for Disease Control and Prevention
sak2 at cdc.gov

  
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From: Morbidity and Mortality Weekly Report,  Vol. 46 (12):258-61,
March 28, 1997.

Foodborne Diseases Active Surveillance Network, 1996

As an important strategy for addressing emerging infections in the
United States, in 1994 CDC began implementing Emerging Infections
Programs (EIPs) in state health departments, in collaboration with
local health departments, academic institutions, and organizations
of health professionals ( 1 ). EIPs are sites that conduct special
population-based surveillance projects, emphasize collaborative
epidemiologic and laboratory projects, and pilot and evaluate
prevention efforts. The primary foodborne diseases component
of the EIP is the Foodborne Diseases Active Surveillance Network
(FoodNet)--a collaborative effort among CDC, the U.S. Department
of Agriculture (USDA), the Food and Drug Administration, and the
EIP sites. The objectives of FoodNet are to 1) determine more
precisely the burden of foodborne diseases in the United States,
2) determine the proportion of specific foodborne diseases
associated with certain contaminated foods or with other exposures,
 and 3) provide the framework to respond rapidly and collaboratively
to emerging foodborne diseases. This report summarizes preliminary
results from FoodNet for 1996, which document regional and seasonal
differences in the incidences of certain bacterial foodborne diseases,
and presents findings of the 1995 baseline survey of clinical
laboratories, which suggests that, for some pathogens, factors other
than differing laboratory practices accounted for regional variations
in incidences.

Active Surveillance
On January 1, 1996, FoodNet began collecting population-based
active surveillance data on culture-confirmed cases of seven
potentially foodborne diseases ( Campylobacter, Escherichia
coli O157:H7, Listeria, Salmonella, Shigella, Vibrio, and Yersinia
infections) among the 13.2 million residents in five EIP sites*. After
identifying the clinical laboratories that routinely tested for infectious
agents the stool specimens of residents of the sites (including
several out-of-state laboratories), these laboratories were routinely
(i.e., weekly or monthly) contacted by investigators to identify cases.
After removal of subsequent isolations from chronic carriers, annual
ncidence rates were calculated using the number of reported cases
as the numerator and census estimates for the individual catchment
areas as the denominator.
*Minnesota, Oregon, and selected counties in California (Alameda
and San Francisco), Connecticut (Hartford and New Haven), and
Georgia (Clayton, Cobb, DeKalb, Douglas, Fulton, Gwinnett, Newton,
 and Rockdale).

In 1996, a total of 7223 culture-confirmed cases of the seven foodborne
diseases were identified from stool specimens or specimens from
normally sterile sites. Incidence rates were highest for
campylobacteriosis (25 per 100,000 population), followed by
salmonellosis (16), shigellosis (9), E. coli O157:H7 infection
(3), Yersinia infection (1), listeriosis (0.5), and vibriosis (0.2). For
all the diseases except salmonellosis, rates varied substantially
among the EIP sites (Figure 1). Rates for campylobacteriosis
ranged from 14 (Georgia) to 58 (California); for shigellosis, from
4 (Minnesota) to 20 (Georgia); for E. coli O157:H7 infection, from
0.6 (Georgia) to 5 (Minnesota); for Yersinia infection, from 0.5
(California) to 3 (Georgia); and for vibriosis, from 0.1 (Connecticut,
Minnesota, and Oregon) to 0.3 (California). Rates also varied by
age: for example, among children aged <1 year, the rate for
salmonellosis ranged from 73 (Connecticut) to 270 (Georgia) and,
for campylobacteriosis, ranged from 25 (Georgia) to 193 (California).

FIGURE 1. Incidence rate of laboratory-confirmed cases of
Campylobacter, Salmonella, Shigella, and Escherichia coli
O157:H7 infections, by selected sites -- Foodborne Diseases
Active Surveillance Network, Emerging Infections Programs, 1996
[Figure not shown]

Isolation patterns varied by season for several pathogens: 50%
of E. coli O157:H7, 35% of Campylobacter, and 33% of Salmonella
were isolated during summer months (June-August). The percentage
of pathogens isolated from normally sterile sites (e.g., blood and
cerebrospinal fluid) was 89% for Listeria, 10% for Vibrio, 9% for
Salmonella, 3% for Yersinia, and 1% each for Shigella and
Campylobacter. Of the 7223 case-patients, 1174 (16%) were
hospitalized; hospitalization rates were highest for persons with
listeriosis (94%), followed by those with Yersinia infection (32%),
E. coli O157:H7 infection (28%), salmonellosis (22%), vibriosis (20%),
shigellosis (14%), and campylobacteriosis (10%). Of the 34 deaths,
16 (47%) were associated with salmonellosis; nine (26%), with
listeriosis; four (12%), with campylobacteriosis; two (6%), with E.
coli O157:H7 infection; two (6%), with shigellosis; and one (3%),
with vibriosis.

Laboratory Survey
To assess variations in laboratory culturing practices, in late 1995
FoodNet investigators mailed a questionnaire to the microbiology
supervisor at each of the 234 clinical laboratories that tested stool
 specimens for infectious agents in the EIP sites. The 230 responding
laboratories performed approximately 22,000 bacterial stool cultures
in August 1995.

Responding laboratories reported that all stool specimens submitted
for bacterial culture were tested for Salmonella and Shigella, and
approximately 99% of specimens were tested for Campylobacter.
Culturing practices for Vibrio, Yersinia, and E. coli O157:H7 varied
substantially among laboratories surveyed. Overall, 20% (range:
9%-43%) of stool specimens were tested routinely for Vibrio; 34%
(range: 13%-52%), for Yersinia; and 47% (range: 6%-82%), for E.
coli O157:H7. Overall, 80% (range: 58%-99%) of all bloody stool
specimens submitted to these laboratories were tested for E. coli
O157:H7.

Reported by: S Shallow, MPH, P Daily, MPH, G Rothrock, MPH,
California Emerging Infections Program; A Reingold, MD, Univ of
California at Berkeley; D Vugia, MD, S Waterman, MD, State
Epidemiologist, California State Dept of Health Svcs. T Fiorentino,
MPH, R Marcus, MPH, R Ryder, MD, School of Medicine, Yale
Univ, New Haven; P Mshar, JL Hadler, MD, State Epidemiologist,
Connecticut State Dept of Public Health. M Farley, MD, M Bardsley,
MPH, W Baughman, MSPH, Atlanta Metropolitan Active Surveillance
Project; J Koehler, DVM, P Blake, MD, KE Toomey, MD, State
Epidemiologist, Div of Public Health, Georgia Dept of Human
Resources. J Hogan, MPH, V Deneen, MS, C Hedberg, PhD, MT
Osterholm, PhD, State Epide- miologist, Minnesota Dept of Health.
 M Cassidy, J Townes, MD, B Shiferaw, MD, P Cieslak, MD, K Hedberg,
MD, D Fleming, MD, State Epidemiologist, State Health Div, Oregon
Dept of Human Resources. Food Safety Inspection Svc, US Dept of
Agriculture. Center for Food Safety and Applied Nutrition, Food and
Drug Administration. Foodborne and Diarrheal Diseases Br, Div of
Bacterial and Mycotic Diseases, and Office of the Director, National
Center for Infectious Diseases, CDC.

Editorial Note: The preliminary findings from FoodNet for 1996
document regional and seasonal differences in the incidences
of certain bacterial foodborne diseases, particularly Campylobacter
infection. Potential explanations for these differences include
regional and seasonal variations in food-handling practices and
the level of contamination of specific food items. Ongoing studies
are directed toward determining whether the variations in laboratory
culturing practices for E. coli O157:H7, Yersinia, and Vibrio are
associated with the regional differences in incidences of the
respective diseases. However, differences in laboratory practices
did not account for variations in the incidences of Campylobacter
and Shigella infections. FoodNet has enabled more precise
calculation of incidences of seven bacterial foodborne pathogens
and monitors the effectiveness of recent food-safety interventions
(e.g., the USDA mandated changes in the meat and poultry
 inspection process in the United States).

Additional studies of the seven diseases will assist in determining
reasons for differing hospitalization rates and causes of death.
FoodNet investigators also are conducting population-based
surveys and surveys of physicians to determine what proportion
of persons with diarrhea seeks medical care and what proportion
of physicians requests specimens from persons with diarrhea.
Analytic studies are being conducted to determine what proportion
of E. coli O157:H7 and Salmonella serogroup B and D infections
are associated with specific foods, foodhandling practices, and
behaviors.

In addition to addressing the burden and specific sources of
foodborne diseases, FoodNet and EIP have provided the
framework for responding to several emerging foodborne
diseases in the United States. For example, FoodNet collaborators
assisted in the investigations of several multistate outbreaks,
including an outbreak of Cyclospora infections associated with
consumption of raspberries imported from Guatemala ( 2 ) and
an outbreak of E. coli O157:H7 infections associated with
unpasteurized apple cider ( 3 ).

On January 1, 1997, the addition of one county in Connecticut and
12 counties in Georgia increased the FoodNet surveillance population
in the EIP sites to 14.7 million persons (6% of the U.S. population). In
addition, collaborators from Maryland and New York joined EIP in
1997 and plan to conduct active surveillance in several counties in
these states. On January 1, 1997, FoodNet initiated active surveillance
for hemolytic uremic syndrome (HUS), a sequela of E. coli O157:H7
and other Shiga toxin-producing E. coli infections. At least three of the
sites will conduct active surveillance for Cryptosporidia and
Cyclospora, and all the sites plan to participate in a case-control
study for Campylobacter infections in late 1997.

References
1. CDC. Addressing emerging infectious disease threats to health; a
prevention strategy for the United States. Atlanta, Georgia: US
Department of Health and Human Services, Public Health Service, 1994.
2. CDC. Outbreaks of Cyclospora cayetanensis infections--United
States, 1996. MMWR 1996;45:549-51.
3. CDC. Outbreaks of Escherichia coli O157:H7 infection and
cryptosporidiosis associated with drinking unpasteurized apple cider--
Connecticut and New York, October 1996. MMWR 1997;46:4-8.