Food-borne outbreakinvestigation

10 June 2014Carmen Varela Martinez

Directive 2003/99/EC:• An incidence, observed under given

circumstances, of two or more human cases of the same disease and/or infection, or a situation in which the observed number of human cases exceeds the expected number and where the cases are linked, or are probably linked, to the same food source.

Food-borne outbreak definition

Aim of food-borne outbreak investigation

Identification of:– Causative agent

– Implicated food

– Contributory factors

In order to:– Control the outbreak

– Prevent similar outbreaks

Steps in food-borne outbreak investigation

Detection

Finding cases

Generating hypotheses

Testing hypotheses and finding the source

Control the outbreak

Epidemiological Surveillance in Spain

Notifiable DiseasesOutbreaks System

Source:Physicians

Microbiology Information SystemSource:

Microbiology Labs

Local

Autonomous Regions

NationalCentre of Epidemiology

International

Detection

Food-borne outbreaks. Spain 1976-2012

*

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

Detection

Detection

No of Cases

654321

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2010

Sampling date

Salmonella Poona cases. Spain 2010

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology

Detection

Detection

Listeria cases. Spain 2012

Index cases

Each colour shows one autonomous regionSource: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology

Detection

Salmonella food-borne outbreaks. Spain 2002-2012*.

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

0

10

20

30

40

50

60

70

Serotyped Serotypes diferent thanEnteritidis andTyphimurium

Phagotyped

% of Salmon

ella outbreaks

Typing

N=425157.4

1.2 1.9

Finding casesCase definition:

Sensitivity versus specificity

Generating hypotheses

Questionnaire for description of the outbreak:

– Disease / Causative agent

– Place: Setting

– Time: Epidemic curve

– Person: age, sex, ocupation, etc.

– Common exposure: food, travel, animal, etc.

Generating hypothesesb.1) Food intake (72 hours before onset of symptoms): Food Branch Batch Place of

acquisition Date of

acquisition Eggs and egg products

Cakes/Ice creams

Milk/ yoghourt

Cheese

Chicken

Pig

Meat products “Embutido”:

salchichón

chorizo

lomo

jamón serrano

jamón york

chistorra

otros:

__________________

__________________

__________________

Sausages

Minced meat

Other meat

Tap water

Bottle water

Generating hypotheses

b.2) Food preferences (food intake per week): Food Never 1 per week 2 per week 3 per week >3 per weekEggs and egg

products

Cakes/Ice

creams

Milk/ yoghourt

Cheese

Chicken

Pig

“Embutido”

Sausages

Minced meat

Other meat

Generating hypotheses

No of Cases Cases < 1 yearCases >= 1 year

654321

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2010

Sampling dateSource: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology

Testing hypotheses, finding the source

EFSA

Epidemiological evidence (whether descriptive or analytical)

– Strong or week

Microbiological evidence– Strong or week

EU summary report on zoonoses, zoonotic agents and food-borne outbreaks 2012. EFSA

Testing hypotheses, finding the source

Testing hypotheses, finding the source

EU summary report on zoonoses, zoonotic agents and food-borne outbreaks 2012. EFSA

EU summary report on zoonoses, zoonotic agents and food-borne outbreaks 2012. EFSA

Testing hypotheses, finding the source

Food-borne outbreaks with unknown causative agent. Spain 2002-2012*.

0

5

10

15

20

25

30

35

40

45

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

% of o

utbreaks 

Year

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

N=8739

Causative agent unknown

2002‐2009 33,382010‐2012 28,17

Χ2=16,99p=0,000038

Testing hypotheses, finding the source

0

5

10

15

20

25

30

35

40

45

50

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

% of o

utbreaks

Year

Microbiological

Epidemiological

Both

Food-borne outbreaks according to the type of evidence. Spain 2002-2012*.

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

N=8739

Testing hypotheses, finding the source

0

10

20

30

40

50

60

70

80

90

100

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

% of o

utbreaks

Year

Food-borne outbreaks with at least one sample analysed. Spain 2002-2012*.

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

N=8739

Testing hypotheses, finding the source

0

5

10

15

20

25

30

35

40

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

% of o

utbreaks

Year

Food-borne outbreaks mentioning a food item. Spain 2002-2012*.

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

N=8604

Testing hypotheses, finding the source

Testing hypotheses, finding the source

Cheese3%

Eggs/egg products45%

Chicken4%

Fish6%

Sellfish8%

Cakes5%

Mix7%

Others22%

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

Food-borne outbreaks according to the reported food. Spain 2002-2012*.

N=8604

Contaminated ingredient

15%

Storage time/temperature 

abuse17%

Inadequate heat treatment

4%

Inadequate chilling11%

Cross‐contamination18%

Infected food handler3%

Other 1%

Unknown31%

Contributory factors reported in food-borne outbreaks. Spain 2002-2012*.

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

N=11550

Testing hypotheses, finding the source

No of outbreaks according transmission mode. Spain 2012*

1%

57%

42%

Food Water Other

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

N=1259

Testing hypotheses, finding the source

Imported food-borne outbreaks according to country of infection. Spain 2002-2012*.

Source: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

Not specified Bulgaria Colombia Cuba Denmark Ecuador Egypt India Italy Morocco Namibia PortugalEscherichia coli 1L.monocytogenes 1Salmonella 1 4S.Typhi/S.Paratyphi 1Shigella 2 2V.cholerae 1Trichinella 1 1Virus hepatitis A 1 1 1 6 1Norovirus 1 1Unknown 1 2 7

TOTAL 2 1 1 1 1 1 1 4 1 10 1 13

Testing hypotheses, finding the source

Control the outbreak

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Facilities inspection

Hygiene education

Unknown

Food handler control

Contact tracing

Specified treatment

Food detention

Cessation of activity

Disciplinary procedure

Deficiency repairing

Desinfection

Other

Isolation

Immunization

Mea

sure

s

No of measuresSource: National Network of Epidemiological SurveillanceElaboration: National Centre of Epidemiology * Provisional data

implemented measures in food-borne outbreaks. Spain 2002-2012*.

N=12848

Conclusions

Typing information added to the epidemiological

data is of great value in the investigation of

food-borne outbreaks.– ECDC is supporting molecular typing initiatives.

Web based tools together with social networks

can facilitate the investigation of food-borne

outbreaks.

Conclusions

Investigation of food-borne outbreaks differs

among EU Member States.

To achieve a higher proportion of food-borne

outbreaks with strong epidemiological and/or

microbiological evidence would lead to a better

prevention and control of them.