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STATEMENT OF
STEPHEN M. OSTROFF, M.D.
ASSOCIATE DIRECTOR
FOR EPIDEMIOLOGIC SCIENCE
NATIONAL CENTER FOR
INFECTIOUS DISEASES
CENTERS FOR DISEASE
CONTROL AND PREVENTION
DEPARTMENT OF HEALTH
AND HUMAN SERVICES
BEFORE THE
AGRICULTURE, NUTRITION AND FORESTRY
COMMITTEE
U.S. SENATE
September 20, 2000
I am Dr. Stephen Ostroff, Associate
Director for Epidemiologic Science, National Center for Infectious
Diseases, Centers for Disease Control and Prevention (CDC).
I would like to thank the Committee for the opportunity to
be here today with my colleagues from the Food and Drug Administration
(FDA) and U.S. Department of Agriculture (USDA)
Today, I will discuss CDC's role in the
area of foodborne diseases and food safety, including how
CDC has worked with other federal partners and used resources
obtained through the National Food Safety Initiative to strengthen
the Nation's ability to detect and respond to emerging foodborne
disease threats. I will also discuss the public health burden
of foodborne illnesses in the United States, highlight our
progress in reducing foodborne illnesses, and provide examples
from surveillance reports and recent outbreak investigations
to demonstrate how National Food Safety Initiative resources
are being applied to today's public health practice.
Today, more than 200 known diseases are transmitted through
food. The causes of foodborne illness include viruses, bacteria,
parasites, toxins, metals, and prions. The symptoms of foodborne
illness range from mild gastroenteritis to life-threatening
neurologic, hepatic, and renal syndromes. We estimate that
foodborne diseases cause approximately 76 million illnesses,
325,000 hospitalizations, and 5,000 deaths in the United States
each year. Of these, known pathogens account for an estimated
14 million illnesses, 60,000 hospitalizations, and 1,800 deaths.
Three pathogens, Salmonella, Listeria, and Toxoplasma,
are responsible for 75 percent of these deaths each year.
Unknown agents account for the remaining 62 million illnesses,
265,000 hospitalizations, and 3,200 deaths.
In the wake of this public health burden on our Nation's
health, I can report significant progress in reducing foodborne
illness. CDC data show that from 1997 to 1999, illness from
the most common foodborne pathogens declined by 20 percent.
This decline represents nearly a million fewer Americans suffering
illness each year from foodborne illness since the launch
of the President's Food Safety Initiative. I am happy to summarize
these data for you this morning.
Many factors may have contributed to these impressive two-year
declines in foodborne illness -- the fact that they were seen
across all of our active surveillance (FoodNet) sites suggests
they are not surveillance artifacts. This further suggests
that preventive measures, including those being implemented
by the FDA and USDA, are working. Let me offer a few examples:
� Campylobacter (the most
common foodborne bacterial pathogen) down 26%: Changes in
poultry processing plants encouraged by USDA's Food Safety
Inspection Service (FSIS) HACCP rule likely contributed here.
� E. coli O157:H7 infections
down 22%: Improved sanitation in slaughter and processing
plants and attention to hamburger cooking temperature likely
contributed here. E. coli causes a serious disease
which often leads to diarrhea and kidney failure, particularly
in young children.
� Salmonella
enteritidis down 48%: FDA, FSIS, state and industry
efforts to decrease contamination of eggs likely contributed
here. The implementation of the Egg Safety Action Plan and
FDA's pending final rule on egg refrigeration and labeling
are expected to contribute to further decline.
� Shigella down 44%: This
decline follows a large outbreak in 1998 traced to imported
parsley. The outbreak showed the need to improve sanitation
on produce farms throughout the continent. Recent FDA/FSIS
Good Agricultural Practices Guidelines focus on this need.
FDA also has increased sampling and detection of imported
produce, and supported education outreach programs in foreign
countries.
� Cyclospora down 70%: This
decline follows rapid FDA action and subsequent production
controls on imported raspberries.
� Salmonella up 2% overall:
This trend is partly due to large outbreaks in 1999 due to
raw sprouts, unpasturized orange juice, and imported mangoes.
New FDA guidance on raw sprouts, pending juice regulations,
and import sampling/detection strategies would be expected
to contribute to future declines in illness.
These few examples show the importance of public health surveillance
data and how such data can be used. Surveillance data document
the incidence and prevalence of foodborne illness, and suggest
where preventive measures, including regulatory action, may
be needed. Over time, surveillance data also help to document
the effectiveness of these preventive measures.
Despite these impressive gains in reducing the burden of
bacterial foodborne illnesses, we need to point out that many
challenges remain. New foodborne pathogens are emerging, old
foodborne pathogens are showing up in new foods, and antimicrobial
resistance in foodborne pathogens is increasing. As we are
here, another hearing is being conducted on the worsening
trends in antimicriobial resistance, which will be a serious
threat in future years.
CDC's Role in Foodborne Diseases
and Food Safety
At its most fundamental level, CDC is the agency that keeps
its finger on the pulse of the Nation's health. CDC is the
cornerstone Federal agency responsible for identifying and
monitoring foodborne and other illness and for documenting
the effectiveness of prevention and control efforts, including
both voluntary and regulatory measures. Using this information,
we then work with partners to develop ways to improve disease
control and prevention actions. CDC collaborates with State
and local health departments, clinicians, academic centers,
industry, other countries, and international organizations.
In food safety, CDC works in very close coordination with
the other agencies represented in today's hearing.
Foodborne and waterborne diseases is a target area
in CDC's plan, Preventing Emerging Infectious Diseases:
A Strategy for the 21st Century. Public health
priorities in the plan are organized under four broad, interdependent
goals, each of which can be applied specifically to the prevention
of foodborne illness: improving surveillance and response
capacity, addressing applied research priorities, repairing
the Nation's public health infrastructure and training programs,
and strengthening prevention and control programs required
to control emerging, reemerging, and drug-resistant infectious
diseases.
CDC plays a critical and unique role as
a monitoring, investigative, and advisory agency that is separate
from regulatory agencies, but that works closely with them.
CDC monitors the occurrence of human foodborne disease in
the United States. This includes not only traditional public
health concerns, such as illness caused by pathogens such
as Salmonella, but also newer foodborne threats such
as the bacteria E. coli O157:H7 and the parasite
Cyclospora. We also monitor levels of antibiotic
resistance in bacteria that cause foodborne illness. CDC works
with State and local health departments to conduct ongoing
surveillance of cases of foodborne illness and to investigate
disease outbreaks, which often provide the first warning of
new or different threats to the food supply. CDC uses both
surveillance data and results of outbreak investigations to
identify the factors responsible for illness so that immediate
control measures can be taken and longer term prevention strategies
can be developed. While other agencies measure success of
interventions via reductions in food contamination, CDC's
role in measuring the success of interventions is to see whether
they translate into reductions in the number of human cases
of foodborne illness. The ultimate test of all prevention
efforts is whether they prevent human illness.
Once an outbreak is detected, the first response is usually
from the State or local health department. CDC will often
be invited by the State health departments to participate
in the investigation if an outbreak is very large or complex,
is thought to involve an unusual pathogen or unexpected food
vehicle, affects multiple states or countries, or when preliminary
investigations do not reveal a source. When investigating
an outbreak of a foodborne illness, public health officials
must combine laboratory diagnostic techniques and epidemiologic
investigative methods to determine the causative agent of
the illness, the food vehicle responsible for transmission,
and the environmental factors that contributed to the outbreak.
If a food is identified as the source of illness, CDC collaborates
with FDA or FSIS on the investigation and control of the outbreak,
based upon which agency regulates the suspected food.
In addition to our surveillance and response activities,
CDC also conducts applied foodborne illness research. Some
examples include developing laboratory diagnostic tests where
none currently exist, such as detection of hepatitis A virus
in food and detection of Norwalk-like viruses or Cyclospora
in clinical specimens and foods; developing methods to
subtype, or "fingerprint", bacteria, viruses, and parasites
causing foodborne illness; conducting risk factor studies
for foodborne illness in special populations, such as the
immunocompromised; and performing cost-effectiveness analyses
of potential prevention measures such as routine use of hepatitis
A vaccine in food workers.
The public health infrastructure is the underlying foundation
that supports the planning, delivery, and evaluation of public
health activities and practices. CDC's ongoing effort to rebuild
the U.S. public health infrastructure that addresses infectious
diseases is critical to improve the capacity of health departments,
health care delivery organizations, and clinical and public
health laboratories to detect and report cases of foodborne
and other illness and to implement prevention and control
strategies. Part of this effort includes enhancing capacity
to respond to disease outbreaks and training public health
professionals to be able to respond to emerging threats now
and in the future. With respect to the prevention and control
of foodborne diseases, these efforts are directed at enhancing
the states' ability to investigate, control, and report all
outbreaks of foodborne diseases.
CDC also engages in educational activities targeted to health
care professionals and the public. Examples of assistance
to health professionals include producing videos on laboratory
methods to diagnose foodborne pathogens and materials on how
to avoid foodborne illness among immunocompromised, high-risk
persons. To educate the public, CDC actively participates
with FDA, FSIS, and other Federal agencies, industry, and
consumer organizations in the Partnership for Food Safety
Education, an ambitious public private partnership created
to reduce the incidence of foodborne illness by educating
Americans about safe food-handling practices through many
activities, including the national Fight BAC!TM
Campaign. The purpose of the Fight BAC!TM Campaign
is to help educate consumers about the problem of foodborne
illness and motivate them to take basic sanitation and food-handling
steps that will reduce the risk of foodborne illness.
The Challenges of Food Safety
Although the United States has one of the safest food supplies
in the world, the public health burden of foodborne diseases
is still substantial, and we continue to face challenges to
the safety of our foods. New foodborne pathogens are emerging,
old foodborne pathogens are showing up in new foods, and antimicrobial
resistance in foodborne pathogens is increasing. The eating
habits of Americans have changed. We now consume more fresh
produce and seafood and demand a constant supply throughout
the year. Changing food habits can result in a changing pattern
of foodborne illness. To meet the demand, an ever increasing
proportion of our food is imported, especially from developing
parts of the world. As a result, we are being exposed to pathogens
not commonly found in the United States, as demonstrated by
the Cyclospora outbreaks associated with imported
raspberries. The array of new products and processing methods,
such as pre-packaged salad mixes, presents another challenge,
as does mass production and distribution of foods, which has
the potential to produce diffuse, nationwide illness outbreaks
of unprecedented scale.
New challenges require new, creative ways to do our job more
effectively and efficiently. The President's National Food
Safety Initiative, launched in 1997, recognizes this need
and is moving our food safety system forward. CDC has been
an active partner in the development and implementation of
the Food Safety Initiative. Our resources under this initiative
have primarily been targeted to harnessing the information
and laboratory technology revolution to propel our Nation's
foodborne disease surveillance system into the 21st century.
FoodNet
I will provide two examples of CDC's progress in this area.
First is the Foodborne Diseases Active Surveillance Network
(FoodNet). The FoodNet system is a joint effort by CDC, FDA,
USDA, and State health departments to capture a more accurate
and complete picture of trends in the occurrence of illness
caused by priority foodborne pathogens. It is built on the
foundation of CDC's emerging infectious disease activities,
which provides the basic infrastructure to conduct active
disease surveillance. Before 1996, the Nation's foodborne
disease surveillance system was based on passive reports of
illness from clinicians and laboratories which were submitted
to local health departments and then onward to the State health
department and from the State to CDC. Such information lacks
timeliness, is often incomplete, and is highly variable from
one place to the next depending on the resources invested
at the state and local level.
FoodNet is part of CDC's Emerging Infections Program (EIP).
CDC funds EIP cooperative agreements with State and local
health departments to conduct population-based surveillance
and research that goes beyond the routine functions of health
departments. In these sites, the program, which usually involves
a partnership between the State health department and an academic
center, canvasses laboratories and other data sources for
illnesses caused by nine different pathogens on an active,
ongoing basis using standardized data collection methods,
standard definitions, and standard techniques. Special case-control
studies are conducted across FoodNet sites in order to identify
the major risk factors for sporadic illness. Community surveys
are conducted to help determine the overall burden of foodborne
illness. These can include mild cases of illnesses which do
not come to medical attention or cases where there is no diagnostic
test performed. Data are electronically submitted to CDC for
timely analysis. FoodNet gives high quality data never before
available and also allows us to make determinations that differences
across sites are real and not due to differing surveillance
intensities or methodologies.
PulseNet
A second system to highlight is PulseNet, a system developed
in partnership with State health departments and the Association
of Public Health Laboratories and a winner of the Ford Foundation's
"Innovations in American Government Award." PulseNet is a
network of molecular subtyping (fingerprinting) laboratories
at State health departments, FDA, USDA, and CDC, which enhances
the ability of laboratory-based surveillance to rapidly identify
clusters of related foodborne infections of certain pathogens,
sometimes scattered over large geographic areas. This system
uses a methodology known as pulsed field gel electrophoresis
(PFGE) to digest bacterial DNA and produce unique patterns.
Like human fingerprints, each bacteria and its offspring have
a unique PFGE pattern. If two bacteria are found with an indistinguishable
pattern, it is likely that they have a common source, meaning
they may be part of an outbreak of many similar cases. CDC
initially standardized PFGE methodology for E. coli O157:H7
and for Salmonella. In 1998, CDC also standardized
PFGE methodology for Listeria, not long before there
was a multi-state outbreak of listeriosis associated with
contaminated hot dogs. Using funds obtained through CDC's
Epidemiology and Laboratory Capacity (ELC) cooperative agreements
and from the Food Safety Initiative, state health laboratories
have obtained PFGE equipment, and CDC has provided training
and standardized methodology to them to test for foodborne
pathogens. USDA and FDA laboratories also participate in the
network to allow comparison between animal, food, and human
isolates. Currently, 48 state public health laboratories in
46 states are linked into this network. Eventually, CDC hopes
to include all state laboratories.
To enhance the power of the PulseNet system, in 1998, CDC
created a national computer database of PFGE patterns that
is housed at CDC. Now states can submit PFGE patterns to the
database over the Internet. The computer then automatically
scans previously submitted patterns searching for matches.
If a match is found, a signal is given to the submitter that
duplicate patterns are present and where they came from, so
that an investigation can begin to look for a common source.
When the system is fully implemented, all of this will happen
in real time, allowing the early warning system for nascent
outbreaks that we all desire.
The impact of PulseNet has been enormous, both in identifying
outbreaks that would otherwise have gone unnoticed, and in
allowing us to focus our investigations to determine the true
source and extent of an outbreak. For example in late 1998,
an increased number of cases of listeriosis were noticed.
Using PulseNet technology, CDC tested the strains from several
states and determined that many had the same PFGE pattern.
Epidemiologic investigations found a strong association with
hot dog consumption in patients with the outbreak strain,
leading to recalls which occurred just before Christmas. CDC
then continued to work with states to test all available Listeria
isolates from patients from the previous summer in order to
determine how many cases and deaths occurred as part of the
outbreak and to confirm that the outbreak is over.
Some of the strains, which were tested, were different from
the outbreak strain. Among these strains, a second cluster
with a common PFGE pattern was found. Investigation of these
cases found they were linked to consumption of a specific
imported cheese. Other small clusters of cases have been identified
and are under investigation. If not for the ability to do
the subtyping, it is unlikely that these outbreaks would have
been discovered and investigated, and prevention measures
would not have been undertaken.
Another PulseNet example involves Shigella, a bacterial
pathogen that can be foodborne but most often is not. The
Minnesota Department of Health, a FoodNet site, routinely
fingerprints Shigella isolates, and, in 1998 they
identified a cluster of strains with a similar pattern. Epidemiologic
investigations found that illness was linked to eating chopped
parsley at two different restaurants. By informing other states
and searching databases for places with an increased number
of cases, similar outbreaks were identified in five other
states and Canada. The Shigella from these outbreaks
also had the same PFGE fingerprint. All of the outbreaks were
parsley associated. Working with FDA, the implicated parsley
was traced to a specific farm. Again, if not for routine utilization
of PFGE, the links between the outbreaks would have been missed,
the source would not have been identified, and the outbreak
would have spread much further.
PFGE is a powerful surveillance tool. It allows us to detect
widely dispersed outbreaks and small clusters that would have
previously been missed. This illustrates a central tenet of
epidemiology: better surveillance leads to better and more
accurate disease detection, which in turn leads to more field
investigations. This causes increased burdens, not only on
CDC and other Federal agencies, but also on State and local
partners.
Therefore, as surveillance improves, more outbreaks, not
fewer, will be detected. However, this should not be interpreted
as a failure. Rather, it represents success, because only
by finding and investigating the outbreaks can we define risks,
develop and implement interventions, and over the long term,
identify and limit the risk.
National Food Safety Initiative at CDC
CDC will continue to direct its resources to developing the
needed public health infrastructure throughout the Nation
to detect, control, and prevent foodborne illness and to strengthen
prevention and control programs required to control emerging,
reemerging and drug-resistant infectious diseases. In short,
CDC, in collaboration with others, will continue to build
State and local health department capacity to conduct appropriate
epidemiologic, laboratory and environmental investigations;
and continue ongoing efforts to inform health professionals
and the public about foodborne illness and prevention.
For example, we will continue to develop a national network
of laboratories capable of using state-of-the-art laboratory
methods and technologies. This includes increasing the number
of States participating in PulseNet, and increasing the number
of pathogens monitored by the system in order to detect additional
outbreaks. We intend not only to expand our development of
state-of-the-art gene-based diagnostic and subtyping tools
for bacteria, but also to develop a comparable system for
identifying viral contaminants. We also will continue to support
a system known as DPDx, which harnesses telemedicine technology
to transmit images of parasites under the microscope to our
experts at CDC for appropriate diagnosis. In addition to our
efforts to improve epidemiology and laboratory capacity, we
intend to work with the States to strengthen their environmental
health capacity. For example, we plan to work with the States
to assess the training needs of food protection specialists
(environmental sanitarians) and develop food safety guidance
for local food protection programs. We also intend to continue
development of school-based prevention and control efforts,
including development of a model coordinated school health
and food safety program. We also will continue to update analyses
and estimates of the public health burden of foodborne disease.
Conclusions
In conclusion, these activities represent a small sample
of how CDC supports its State and local partners and other
Federal agencies in monitoring, controlling, and preventing
foodborne illness. Foodborne diseases remain a challenge for
public health. To address this challenge will require continued
investments in our public health infrastructure and strong
partnerships among State and local health departments and
Federal agencies.
Thank you for the opportunity to discuss the surveillance
of foodborne disease. We will be happy to answer questions
you or other members of the Committee may have.
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