1Surveillance and outbreak detection Foodborne Disease Outbreak Investigation Team Training: Module...

1Surveillance and outbreak detection

Foodborne Disease Outbreak Investigation Team Training:

Module 2 – Foodborne Disease Surveillance and

Outbreak Detection


Module Learning ObjectivesAt the end of this module, you will be able to1.Describe the surveillance of foodborne illness

through notification/complaint systems.2.List ways to improve the accuracy of a food

history obtained in a foodborne illness complaint.3.Describe the surveillance of foodborne illness

through pathogen-specific surveillance.4.Recognize a possible outbreak using a

notification/complaint system or pathogen-specific surveillance.

5.Describe the role of local public health in national pathogen-specific surveillance.


Foodborne Disease Surveillance

• Many ways to find out about cases of foodborne illnesses and outbreaks

• Two primary means – Foodborne illness notification/complaint

systems– Pathogen-specific surveillance (notifiable

disease reporting)


Foodborne Illness Notification/Complaint

Systems


Notification/Complaint Systems• Complaints of illness among individuals and

groups reported by affected members of the community (and others)

• Includes any illness thought to be related to food

• Common exposures are used to link cases together

> Notifications/complaints


Steps in Receiving Complaints Illness in individual

or group

Interview of complainant

Documentation of information

Key information entered into log

Complaint to local health department

Evaluation of reports over time

for outbreaks

Routine review of log

Evaluation of individual reports

for immediate action


Starts with complaint by

consumer

Common exposures link

cases over time


Interview of Complainant

• Who is affected?

• What is the problem?

• When did problem occur?

• Where?

• Why/how?

(e.g., name, age, and sex) (e.g., symptoms, diagnosis)

(e.g., date/time of onset)

(e.g., travel, water, contact with ill persons or animals, suspect food or meal, food history)

(e.g., place of residence and exposure)


Example in appendix


Collecting Food Histories

• Complete food history important including– Foods eaten in 5 days before onset of illness

If illness suggestive of norovirus, focus on 24-48 hours before illness.

If >1 ill person, focus on shared foods/meals. – ALL foods eaten during time period of interest

(unless focusing on shared foods/meals)– Details of named events, food establishments,

or suspect food products• Information on non-food exposures



Small Group ExerciseDivide into groups of two. One person will be the interviewer; one will be the complainant.

1.The interviewer should solicit a 5-day food history from the complainant.

2.The complainant should respond to questions as if they just developed symptoms that day and based on what they really ate in the last 5 days.

3.Was it easy or difficult? Did you get a complete food history? What approaches were helpful?

Time: 10 minutes

Be prepared to share your experience with the class.


Improving Food Histories

• Look at a calendar• Describe each meal in time period• Identify key events to jog memory• Review receipts or menus• Enlist help of dining partners• Consider specific list of foods • Think about food preferences• Rule out or rule in specific foods

Have complainant



Entering Information into Log

• Extract key information from the complaint to facilitate examination of reports over time− Date of illness onset− Predominant signs and symptoms− Name of food thought to have caused illness− Names of eating places or gatherings− Source of water and type− Other exposures

• Transfer information carefully• Use consistent abbreviations and codes



Evaluation of ComplaintsIndividual reports of concern:• Symptoms suggestive of serious illnesses • Laboratory-confirmed diagnoses• Reports of obvious food safety problems• Group illnesses thought to be due to an identified,

shared exposure



Group Illnesses Due to Identified, Shared Exposure

Illnesses are likely to be related to an identified, shared exposure (e.g. particular meal, event, or establishment), if group members have:•Similar signs and symptoms•Shared a food or meal prior to onset of illness and had no other common exposures•Onset and nature of illness is consistent with identified shared exposure



Class Question

Person developed diarrhea after eating at a restaurant. Neighbors who ate at the restaurant also are sick but complainant does not know their symptoms.

Likely

Unknown

Unlikely

Which of the following group illnesses are likely to be due to the identified restaurant exposure?

Four friends develop nausea and vomiting, facial flushing, headache, and itching skin within an hour of eating fish at a restaurant.

Family members develop bloody diarrhea within hours of eating at a restaurant.


Due to Exposure


Evaluation of Complaints (cont’d)Looking at reports over time• Multiple individual complaints with same exposure

(e.g., same food establishment or food)• Multiple individual complaints with clustering by

time, place, or person• Overall increase in complaints



Response to Notifications/Complaints• Notify epidemiology unit/communicable disease staff of

laboratory-confirmed diagnoses.• Refer food safety problem to agency with regulatory

authority.• Alert appropriate persons if possible outbreak detected.• Prioritize follow-up of commercial

establishments.



Follow-up of Commercial Establishments

Rational approach to follow-up•As required by local law/statute or•If complainant observed specific food safety problem or•If two or more persons (not from same household)

– Have similar illness – Shared history of eating at

establishment– Onset and nature of illness

consistent with shared foods



Group Exercise

1. Is the number of complaints what you would expect for the period covered?

2. Are there individual complaints of concern?

3. Are there common exposures (e.g. foods, establishments) across complaints signaling an outbreak?

Divide into groups by table. Study the foodborne illness log at the end of this module spanning a 2-week period and determine:

Time: 10 minutes

Be prepared to share your thoughts with the class.


Strengths of Notification/Complaint Systems

Primary means to detect outbreaks that are•Localized (involving only one jurisdiction)

•Due to diseases with a short incubation period



Notification/Complaint System Issues• Inaccurate and incomplete food histories• Large numbers of complaints• Anonymous complaints• Complaints with unknown causative agent

– Inability to exclude unrelated cases– Inability to link cases based on illness unless symptoms very unique or cases report similar exposure



Pathogen-specific Surveillance


Pathogen-specific Surveillance• Also called “reportable diseases,” “notifiable

diseases,” or “laboratory-based reporting”

• Reports of individual laboratory-confirmed cases of foodborne disease by medical and laboratory staff with submission of clinical isolates, where requested

• Only covers diseases selected by public health agency

• Cases linked to each other by common pathogen

> Pathogen-specific


Steps in Pathogen-specific SurveillanceIllness in individual

Analysis of cases for clusters/outbreaks

Individual seeks health care

Specimen collected

Diagnosis by health-care provider/laboratory

Initial report to health department

Submission of isolate to

public health laboratory

Follow-up interview of

case

Further characterization

Entry into electronic database

Forward to CDC

> Pathogen-specific

Starts with positive lab

resultCommon

pathogen links cases over time


Initial Report

• From health-care provider or laboratory

• Standardized form (often pathogen-specific)

• Information of interest − Patient identifiers− Basic demographic

information− Clinical information− Laboratory results

> Pathogen-specific

Example in appendix


Follow-up Interview of Case

• To identify potential exposures leading to illness

• Similar to interview for notification/complaint system but tailored to specific pathogen− High-risk food exposures for agent− Other exposures related to agent (e.g.,

contact with ill people, animals, water)

• Often occurs weeks after exposure leading to illness resulting in poor recall

> Pathogen-specific


Laboratory Characterization of Pathogen

• Submission of patient isolate to public health laboratory for confirmation and subtyping

• Increased detail about the pathogen (e.g., serotyping, PFGE) improves

– Recognition of clusters

– Linking an outbreak with an exposure

• Most critical with common pathogens

> Pathogen-specific


Analysis for Clusters

• Examine cases by pathogen over time using– Different levels of specificity of pathogen (e.g.,

species, selected subtypes)– Subgroups of population (certain time, place,

or person characteristics)• Look for increase in number of cases over

expected or baseline, indicating a cluster

> Pathogen-specific


Analysis by Causative Agent

Month of Diagnosis

Nu

mb

er

of C

ase

Lab-confirmed salmonellosis cases by month of diagnosis, 2010.

All Salmonella

> Pathogen-specific


Month of Diagnosis

Nu

mb

er

of C

ase

Lab-confirmed salmonellosis cases by month of diagnosis

Salmonella Javiana

All Salmonella

Analysis by Causative Agent Subtype

> Pathogen-specific


Month of Diagnosis

Nu

mb

er

of C

ase

s

Lab-confirmed salmonellosis cases by month of diagnosis

Salmonella Javiana

All Salmonella

Analysis by Causative Agent and Age Group

Salmonella Javiana among persons <5 yrs.

> Pathogen-specific


Strengths of Pathogen-specific Surveillance

Primary means to detect outbreaks that are•Wide-spread (i.e., multijurisdictional),•Due to prolonged low-level food contamination, or •Due to diseases with a long incubation (e.g., hepatitis A)

> Pathogen-specific


Pathogen-specific Surveillance Issues

• Incomplete detection and reporting

Population

Person Becomes Ill

Person Seeks Care

Specimen Obtained

Lab Tests for Organism

Culture-confirmed Case

Reported

> Pathogen-specific



• Elapsed time

• Incomplete detection and reporting Patient

eats food

Patient becomes ill

Stool sample

collected

Salmonella identified

Isolates received by

public health lab Case

confirmed as part of

cluster

Incubation period=1-3 d

Time to contact with health care=1-5 d

Shipping time=0-7 d

Serotyping and PFGE=2-10 d

Time to diagnosis=1-3 d

Elapsed Time for Salmonella Reporting

> Pathogen-specific



• Availability of isolate for further characterization

> Pathogen-specific

• Elapsed time

• Incomplete detection and reporting


Comparison of Surveillance Systems

Notification/ complaint system

Pathogen-specific surveillance

Types of foodborne illnesses detected

All Only selected diseases

Initiating event Consumer complaint Positive lab resultMeans to link cases Common exposures Same pathogenLinkage of cases across jurisdictions

Not usually Yes

Exclusion of unrelated cases

Difficult Good

Speed Fast Relatively slow

Types of outbreaks best detected

Localized outbreaks; short incubation

illnesses

Widespread; low-level contamination

events; long incubation illnesses


National Pathogen-Specific Surveillance Systems


• NNDSS (National Notifiable Disease Surveillance System)− Data from pathogen-specific surveillance forwarded to

CDC (minimal case information)− Statistical algorithm used to identify increases

• PulseNet (National Molecular Subtyping Network for Foodborne Disease Surveillance)− Laboratory network that uses standardized pulsed field

gel electrophoresis (PFGE) methods− PFGE patterns uploaded by labs for STEC, Salmonella,

Shigella, Listeria, Campylobacter− Comparisons of patterns to identify clusters

National Pathogen-specific Surveillance

> National surveillance


National Pathogen-specific Surveillance• CaliciNet (National Electronic Norovirus Outbreak Network)

− Laboratory network that subtypes/sequences norovirus isolates related to outbreaks

− Data uploaded to CDC allows linkage of outbreaks and identification of new variants

• NARMS (National Antimicrobial Resistance Monitoring System—enteric bacteria)

− Submission of Salmonella, Shigella, E. coli O157, Campylobacter, and non-cholerae Vibrio to CDC

− Determines trends in antimicrobial resistance



Role of Local Health Departments

• Local pathogen-specific case reports and laboratory results feed into national surveillance

• Important for local health departments to − Collect data in format consistent with other

investigators.− Streamline reporting and isolate submission.− Share case reports with state and submit

patient isolates to public health laboratory as quickly as possible.

− Use national systems to learn about outbreaks in other jurisdictions.



What difference does one local case make?

6

1

11

1

• Two E. coli O157:H7 infections in MN with same PFGE pattern; both ate tenderized steaks

• Through PulseNet, single cases identified in KS and MI; both ate tenderized steaks

• Steaks eaten by cases from same plant

• Recall of 739,000 lbs. of beef

• Outbreak generated high levels of concern about needle/blade tenderized steaks



Quick Quiz


Quick Quiz

1. Typically common exposures are used to detect outbreaks through a foodborne illness notification/complaint systems whereas a common pathogen is used to detect outbreaks through pathogen-specific surveillance systems

A. True

B. False


Quick Quiz2. Illnesses in a group are likely to be related to an

identified, shared exposure (e.g. particular meal, event, or establishment), if group members have which of the following?

A. Ill persons all have the same symptoms.

B. Ill persons shared food or a meal prior to onset of illness and had no other common exposures.

C. Onset of the illness is consistent with the timing of the exposure.

D. All of the above


Quick Quiz

3. Which of the following can improve the accuracy of a food history solicited during a foodborne illness complaint?

A. Have case look at a calendar and identify key events to jog memory.

B. Have case review credit card or cash register receipts to identify where or what they ate.

C. Enlist help of dining partners.

D. All of the above


Quick Quiz

4. All of the following are true of pathogen-specific surveillance EXCEPT

A. Detects all types of foodborne illness.

B. Relies on reports from health-care providers and clinical laboratory staff.

C. Is the primary means to detect widespread outbreaks such as multistate outbreaks.

D. Has an inherent lag in reporting due to time necessary to confirm pathogen through laboratory testing.


Quick Quiz

5. All of the following are important roles for local health departments in national pathogen-specific surveillance EXCEPT

A. Collect information on local cases in a format consistent with other investigators.

B. Share case reports with state health department in a timely fashion.

C. Be alert to outbreaks in other jurisdictions.

D. Submit all patient isolates directly to CDC.

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