Outbreak Investigation

Outbreak: Tell-Tale Signs,

Investigations, Actions & Solutions

SILVEROSE ANN A. ANDALES-BACOLCOL, M.D.,

FPCP, FPSMID

Internal Medicine and Infectious Diseases

OUTLINE of this LECTURE:

I. Definition of terms

II. How outbreaks are recognized

III. Reasons for investigating outbreaks

IV. Constraints of outbreak investigation

V. Infection Control Measures

VI. Preparing for the Investigation

VII. Steps in conducting an outbreak investigation in health care facilities

VIII. Case Study


A. What is an outbreak?

An incident in which two or more people who

are thought to have a common exposure

experience a similar illness or proven

infection.

The occurrence of more cases of a disease

than expected:

in a given place

among a specific group of people or

population

in a particular period of time


B. Epidemic

- same as outbreak but more widespread or

prolonged

C. Healthcare-associated infections

- are infections that occur in patients or healthcare

workers as a result of healthcare interventions

D. Hospital-acquired infections

- Infections acquired during hospital stay which were

not incubating at the time of admission


E. Health Care Facilities

- Hospital

- Private physician’s office

- Outpatient clinic

- Dialysis centers

- Ambulatory surgery

- Endoscopy units

- Long term care facilities

- Nursing homes

- Rehabilitation centers

- Institutions for mentally or physically handicapped

II. How are outbreaks recognized?

A. By the clinician, infection control

professional, nurse, or medical staff

B. By the laboratory personnel or

microbiologist

C. By the patient or patient’s family

D. Hospital or healthcare-associated

infection routine surveillance data

E. Unusual agent, site or host

When to Consider Nosocomial Transmission

of Infectious Diseases?

A cluster of similar infections occurs on one hospital

unit or among similar patients

A cluster of infections associated with invasive devices

occurs

HCWs and patients develop the same type of infection

A cluster of infections with organisms typically

associated with hospital-acquired infections (MDR or

opportunistic organisms)

Determine Risk Factors for Disease or

Nosocomial Infection

Host risk factors for HAI

Invasive devices

Severity of illness

Underlying diseases (Malignancy, HIV)

New technology (Chemo agents)

Environmental risk factors

Location (ICU vs. Ward)

III. Reasons for investigating outbreaks

A. Prevent additional cases in the current outbreak

B. Prevent future outbreaks

C. Assess prevention interventions

D. Learn about a new disease

E. Learn something new about an old disease

• New sources

• Unusual modes of transmission

• Complications of new procedures

F. Reassure the public

G. Minimize economic and social disruption

Negative Effects of Outbreaks

Outbreaks cause

Morbidity, mortality

Prolongation of stay

Additional procedures

Increases cost

Bad reputation

IV. Constraints of Outbreak Investigation

A. Urgency to find source and prevent

cases

B. Pressure for rapid conclusions

C. Pressures because of legal and

financial liability

D. Delays can limit human/

environmental samples for testing

V. Infection Control Measures

Introduce preventive interventions before

initiating or completing an investigation.

Handwashing in-service sessions

Close a unit to new admissions

Remove a product or device

Carefully weigh the potential benefit of more

drastic measures against the potential harm to

patients currently residing in the facility

http://www.clker.com/cliparts/f/b/2/f/1238968076936815408scott_kirkwood_scales.svg.hi.png


All levels of the health care facility’s personnel

must be committed.

Hospital Administration

Infection Control Unit

Chief of the affected service

Head Nurse or Supervisor

Head of Microbiology

Health care professionals (Doctors, nurses)


Consider availability of microbiologic isolates

for antimicrobial sensitivity (or molecular

typing)

Inform Microbiology Lab early

Save specimens and isolates

Be alert for additional isolates that may be

part of the outbreak


Identify the following:

Resources (personnel, supplies, laboratory)

Lead investigator

Person responsible for statistical analysis of

the data

VII. STEPS IN CONDUCTING AN OUTBREAK

INVESTIGATION

Step 1: Learn about the topic

Step 2: Establish the Existence of an Outbreak

Step 3: Verify the Diagnosis

Step 4: Define and Identify Cases

Step 5: Describe and orient the data in terms of time, place, and person

Step 6: Develop Hypotheses

Step 7: Evaluate Hypotheses

Step 8: Refine Hypotheses and Draw Conclusions

Step 9: Implement Control and Prevention Measures

Step 10: Communicate Findings


Research about the disease

through

Infectious Diseases

practitioner

Clinical Epidemiologist

Laboratory personnel

Infection control/ Infectious

Diseases textbooks

Medical Journals

Step 2: Establish the Existence of an

Outbreak

IS THIS AN OUTBREAK?

More cases than expected in a given place over a given time.

Determine the expected number of cases for the area in the given time frame.

Compare the current number of cases with the number from the previous weeks, months or years

Hospital surveillance records

Hospital discharge records or census

Morbidity and mortality records


Outbreak

IS THIS A PSEUDO-OUTBREAK?

• Clusters of positive cultures in patients without evidence of disease (colonization)

• A perceived increase in infections because surveillance was not previously being conducted or because surveillance definitions, intensity or methods have changed


Outbreak

What could cause an artificial increase (pseudo-outbreaks)?

Alterations in surveillance system: New personnel

New definition

New case finding method

New procedure in reporting

Increased awareness

New Laboratory procedure New diagnostic tests, laboratory equipment

New technician

New susceptible population New ward, increase in size of population


Ensure that the disease has been properly

diagnosed.

Be certain that the increase in diagnosed cases

is not the result of a mistake in the laboratory.

Confirm the diagnosis:

Clinical syndrome (signs & symptoms)

Epidemiologic risk (person, place, time)

Laboratory & diagnostic tests


Establish a case definition

Inclusion criteria:

A. Clinical criteria (symptoms, signs & onset)

B. Epidemiologic criteria (person, place, time)

C. Laboratory criteria (culture results & dates)

Case Classification:

A. Suspect/Possible- fewer of the typical clinical features

B. Probable- has the typical clinical features of the disease without laboratory confirmation

C. Confirmed- has the typical clinical features of the disease and laboratory confirmation

Exclusion Criteria (for suspect and probable)


Identify and count cases

Interview staff, patients

Review patients records, log books, employee health records

Review lab records

Infection surveillance data

Passive surveillance

Send out letters describing the situation and ask for reports

Active surveillance

Do telephone surveys or visit the facilities to collect information


Collect Case Data

Identifying information

Demographic information

Clinical information

Risk factor information

Underlying diseases

Invasive procedures

Surgical risk factors

Laboratory test results


Complete Line Listing

A table consisting of important variables such as

identification number, age, sex, signs& symptoms,

lab test results.

New cases are added to a line listing as they are

identified.

Case

#

Initials Date

of

report

Date

of

onset

Diagnosis Age Sex symptoms P.E. Labs

1 MC 2/13 2/4 HAP 67 M Cough,

fever

crac

kles

CXR,

Step 5: Describe and Orient the Data in Terms

of Time, Place, and Person

Descriptive Epidemiology

Provide a comprehensive

description of an outbreak

by showing its trend over

time, its geographic extent

(place), and the populations

(people) affected by the

disease.

Time: Epidemic Curve

Epidemic curve

A graph of the number of cases by their

date of onset

Gives a simple visual display of the

outbreak’s magnitude and time trend.

Y axis= # of cases

X axis= date of onset/time

Epidemic Curve

Cases

Day

s >probable

period of

exposure

<<Minimum>>

<<incubation>

>

<Duration of outbreak>

<<<<<<<<<< Maximum incubation >>>>>>>>>>

Epidemic Curve

Common Source

8

7 14

6 13

2 3 12 12

4 1 5 11 9 10 11

1 2 3 4 5 6 7 8 9 10 days

Continuous Source

7

2 6 8 10 13

1 3 4 5 11 9 12

1 2 3 4 5 6 7 8 9 10 11 12 12 days

Person to Person Spread

day

s

Place: “Spot Map”

Plotting cases on a map

Leads on nature & source of outbreak

Provides information on the geographic

extent of a problem

Useful to track spread by water, air,

person to person, distribution route of

contaminated item

Indicate occurrence of cases & not rates

Ground floor 2nd floor

Blue Unit (vacant)

Green Unit

Red Unit

Brown Unit

Social Admin

Kitchen

Laundry Clinics

Services

Business

OfficeClasses

Technical

3

24

8

6

2

7

4514

9

113

12 11 10

18

17

16

15

2322

21

20

19

29

28

2726

25

3332

3134

31

30

33

3536

37

1 2

3

4

8

7 65

12

11

10

9

17

16

1514

13

24

1918

23

22

21

20

27

26

25

28

29

30

31

32

33

35

36

37

38

39

40

4142

Person

Determine what populations are at risk for the disease by characterizing by person.

Age, gender

Health status:

Increased susceptibility

Risk factors

Underlying disease

Exposures

Procedures

Drug, IV line


Formulate a hypothesis to explain why and how the

outbreak occurred based on results of preliminary

investigation.

Hypothesis should address the source of the agent,

the mode of transmission, and the exposures that

caused the disease.

Clues from clinical syndrome

Clues from etiologic agent

Clues from case interviews (have in common?)

Clues from existing knowledge base


Comparison of the hypotheses with the established facts.

Analytic Epidemiology

Cohort studies Compare groups of people who have been exposed

to suspected risk factors with groups who have not been exposed.

Case-control studies Compare people with disease (case patients) with a

group of people without the disease (controls)

Statistical Methods

Lab and Environmental Studies

Step 8: Refine Hypotheses and Draw

Conclusions

When an outbreak occurs, you

should consider what questions

remain unanswered about the

disease.

Draw conclusions from descriptive

or analytic studies

Causal inferences

Step 9: Implement and Evaluate

Control and Prevention Measures

Should be implemented early

Control strategies:

Reduce contact between susceptibles and potential infectives

Reduce probability source is infective

Reduce infectiousness of infectious source

By treatment

Reduce susceptibility of susceptible hosts

By treatment/prophylaxis or vaccination

Interrupt transmission

Physical/Chemical methods

Environmental/Engineering methods

Prevention at Source of Infection

Human source:

Isolation or treatment of the

human source

Length of time the patient is

infectious after treatment

must be known

Prevention of Transmission

Contact and indirect contact:

Prevent contact, wear gloves if contact

is necessary, handwashing

Airborne or Droplet:

Wearing mask with sufficient filtering

ability.

Simple surgical mask sufficient for

large droplet (as long as the mask is

dry)

Masks with HEPA type filters for droplet

nuclei

Food and water borne:

Avoid suspected food and water

Prevention: Protection of At Risk Person

Protection of susceptible

individuals

Immunization (passive or

active, if time permits)

Chemoprophylaxis


1. Communicate preliminary assessments

and recommendations (letter, memo)

Communicate any changes necessitated by

the outbreak analysis to the appropriate

departments

2. Prepare interim/final report

Issue a concluding report to the hospital or

healthcare facility committees

VIII. CASE STUDY 1

An ICC nurse receives a report from the NICU of an increased number of cases of sepsis 2 to Burkholderia cepacia bloodstream infection among newborns who were delivered via normal spontaneous delivery from October 1-31, 2015.

For the month of October 2015, 16 out of 59 newborn babies were treated for sepsis. For the 16 patients, blood cultures were taken during the first few hours of life (ranging from 6 hours to 24 hours). All blood cultures were positive for Burkholderia cepacia.

OUTBREAK INVESTIGATION:

CASE STUDY

Step 1: Learn about

the topic

The ICC nurse looks up Burkholderia

cepacia in her desk copy of Bergy’s

Manual of Systematic Bacteriology

and Infectious Diseases textbook by

Mandell. She found out that

Burkholderia cepacia is a gram

negative bacillus commonly found in

soil and moist environments and

capable of surviving and growing in

nutrient-poor water. It is an important

opportunistic pathogen in

hospitalized and

immunocompromised patients.


CASE STUDY

Step 2: Establish

the existence of an

outbreak

The NICU averages about 2 %

infections per month. The rate of

infection appeared to begin to rise

around May 2015.

September’s BSI rate was 3% and

October’s rate was 27%.

There was no past record of BSI

caused by Burkholderia cepacia.

However, there were past records of

BSI caused by other organisms

(Pseudomonas aeruginosa and

Staphylococcus aureus)


CASE STUDY

Step 3: Verify the

diagnosis

The ICC nurse reviewed the charts

and culture results of the 16 patients

who developed BSI.

She visited 5 of the patients with a

positive culture for B. cepacia who

were still admitted.

She asked the medical and nursing

staff from NICU and DR if there were

any new personnel, new practices,

equipment or solutions used.


CASE STUDY

Step 4: Define and

Identify Cases

The initial case definition is, “Any

newborn baby developing a BSI

following normal spontaneous

delivery performed in the past 6

months. ”

The ICC nurse called the micro lab

and asked for 2 reports:

one screening for Blood cultures from

the NICU and another screening for

any positive Burkholderia cepacia

cultures from the NICU from May 2015

to present.


CASE STUDY

Step 5: Describe

and Orient the Data

in terms of time,

place, and person

All charts were reviewed using a data

collection form developed by the ICC.

Seven additional BSI’s were identified

related to October 2015 deliveries.

Burkholderia cepacia caused five of

the infections.


0.0

5.0

10.0

15.0

20.0

May Jun Jul Aug Sep Oct Nov

Burkholderia

others


10/5

Place

A total of 59 babies were delivered in the

month of October. 35 babies were delivered

via NSD while 24 were via CS. All 16 babies

with BSI were delivered via NSD in Delivery

Room # 3.

NSDs are performed in DR # 3 and 4.

Cesarean Deliveries are performed in DR # 1

and 2

Person

Obstetrician X is associated with 9/16 deliveries of

newborns who developed Burkholderia cepacia BSI.

She has been practicing for 10 years in the hospital.

Nurse A, a DR nurse assisted the deliveries of 16/16

known Burkholderia cepacia BSI cases. Records

showed that she was newly hired and started on

October 1, 2015

Nurse B, a NICU nurse performed newborn care to

8/16 babies who developed B. cepacia BSI. She has

been employed for 5 years.


CASE STUDY

Step 6: Develop a

Hypothesis

It was decided to narrow down the

case definition to:

A BSI that is culture positive for

Burkholderia cepacia in a newborn

patient who was delivered via NSD in

the month of October 2015.

The tentative hypothesis is that

patients are being exposed to

Burkholderia cepacia in the Delivery

Room or NICU.


CASE STUDY

Step 7: Test the

Hypothesis

The ICC nurse notes that Obstetrician

X was involved in 9/16 cases,

Nurse B was involved in 8/16 cases,

and Nurse A was involved in all 16/16

cases.

She decides to determine if their

presence during these deliveries is

significant.


CASE STUDY

Step 7: Test

Hypotheses

The ICC nurse reviewed perinatal and

intra-operative care by interviewing

obstetricians, OB and Pedia residents, and

other D.R. and NICU personnel and by

observing a NSD procedure performed by

Obstetrician X in D.R. # 3 where both Nurse

A & Nurse B were assisting.

Nurse A prepared the patient in labor

prior to NSD. Aseptic technique was

performed. Cotton cherries pre-soaked in

betadine solution was used for cleaning

the perineal area. The umbilical cord was

clamped using sterile clamps and was cut

by a disposable sterile blade.


CASE STUDY

Step 7: Test

Hypotheses

Nurse B assisted the Pediatrician in

performing newborn care. Aseptic

technique was performed while handling

the baby. Sterile suction tubing was used

for suctioning of airways. The newborn

was bathed using pre-boiled water. Cord

care was done using 70% isopropyl

alcohol.


CASE STUDY

Step 7: Test

Hypotheses

Environmental cultures were done to

determine the source of the outbreak.

A culture of the ff. were done:

Cotton cherries pre-soaked in

Betadine solution in DR #3

Betadine solution stored in big

bottles at DR #3

Kelly pads in DR# 3

Pre-boiled water used for bathing

newborns

Bath tub used during bathing of

newborns


CASE STUDY

Step 7: Test

Hypotheses

Result of cultures:

Cultures of cotton cherries pre-

soaked in Betadine solution in DR #3

grew Burkholderia cepacia.


CASE STUDY

Step 8: Refine

Hypotheses and

Draw Conclusions

Newborn babies who were delivered

via NSD in October 2015 developed

Bloodstream infection due to

exposure to Burkholderia cepacia in

Delivery Room # 3.

The technique used by Nurse A in

preparing patients in labor by using

cotton cherries pre-soaked in

contaminated Betadine solution for

cleaning the perineal area caused the

exposure of newborn babies to B.

cepacia during delivery.


CASE STUDY

Step 9: Implementing

Control and

Prevention Measures

The ICC nurse recommends a change in

procedure in preparing patients in labor

prior to NSD.

Cherries pre-soaked in betadine

solution used for prep were not allowed

in the DR. Sterile cotton cherries packed

for single use and Betadine solution

stored in small sterile containers were

recommended.

Aseptic technique during delivery and

newborn care was reinforced.

Nurse A was required to attend in-

sevice ICC seminar.


CASE STUDY

Step 10:

Communicate

Findings

All staff was informed of findings

and the procedure change.

A written summary of findings was

distributed to appropriate staff.

STEPS IN CONDUCTING AN OUTBREAK

INVESTIGATION


Step 2: Establish the Existence of an Outbreak



Step 5: Describe and orient the data in terms of time, place, and person



Step 8: Refine Hypotheses and Draw Conclusions

Step 9: Implement Control and Prevention Measures


VIII. CASE STUDY 2

On March 2015, the ICU Link Nurse was the charge nurse on

duty. Upon updating the cultures of patients, the link nurse has

noticed that 4 out of 10 patients in the ICU have growth of

Klebsiella Pneumoniae Carbapenemase (+) in their cultures.

The Link Nurse immediately notified the Infection Prevention

and Control Office. The surveillance coordinator together with

the Link Nurse conducted an on-the-spot audit of Infection

Prevention and Control Practices of all healthcare workers at the

ICU and reviewed the interactions that occurred with the

patients.


CASE STUDY

Step 1: Learn

about the

topic

The link nurse reads about Klebsiella

pneumoniae carbapenemase from

the Infectious Diseases textbook by

Mandell. She found out that Klebsiella

pneumoniae carbapenemase is a gram

negative bacteria which develop

resistance to most antibiotics including

cabapenems. It is a common cause of

nosocomial infections such as UTI,

pneumonia, and meningitis. It is an

important opportunistic pathogen in

hospitalized and immunocompromised

patients.


CASE STUDY

Step 2: Establish

the existence of

an outbreak

The rate of infection due to KPC at

the ICU appeared to begin to rise

around March 2015.

The KPC HAI rates for the past 6

months were reviewed.

There were no HAIs 2 to KPC last

October, November, January and

February 2015.

There was a past record of HAI 2 to

KPC last December (2 cases of

UTI).


CASE STUDY

Step 3: Verify

the

diagnosis

The ICU link nurse reviewed the

charts and culture results of the 4

patients who developed HAI 2 to

KPC.

She correlated the culture results

with the clinical findings of the

patients.

Patient A.N.- VAP 2 to KPC

Patient B.L- VAP 2 to KPC

Patient N.D.- CAUTI 2 to KPC

Patient S.R.- Infected Decubitus

ulcer 2 to KPC


CASE STUDY

Step 4: Define

and Identify

Cases

The initial case definition is, “Any

ICU patient developing a HAI

secondary to KPC in the month of

March 2015. ”

The ICU link nurse called the

micro lab and asked for a report:

A report screening for any

positive culture of Klebsiella

pneumoniae carbapenemase from

the ICU from March 1 to 31, 2015.


CASE STUDY

Step 4: Define

and Identify

Cases

Line List:

Name Isolate Source Room # Date

collected

Date

admitted

at ICU

Date

transferred

to floor

A.N. (+) KPC ETA ICU 2 3/12/15 3/10/15 3/15/15

B.L. (+) KPC ETA ICU 2 3/8/15 3/4/15 3/10/15

N.D. (+) KPC Urine ICU 5 3/5/15 3/2/15 3/15/15

S.R. (+) KPC Wound ICU 9 3/8/15 3/5/15 3/11/15


CASE STUDY

Step 5: Describe

and Orient the

Data in terms of

time, place, and

person

All ICU charts were reviewed using

a data collection form developed by

the IPCO.


0.0

5.0

OCT NOV DEC JAN FEB MAR

KPC

others

Place

ICU 2 = 2 CASES (Patients B.L. & A.N.)

ICU 5 = 1 CASE (Patient N.D.)

ICU 9 = 1 CASE (Patient S.R.)

Person

RISK FACTORS FOR KPC HAI:

Patient A.N. was intubated since 3/08/2015. He is under the

care of Dr. B. He was cared by Nurse Love on 3/8/2015.

Patient B.L. was intubated since 3/4/2015. He is under the care

of Dr. A. He was cared by Nurse Competence on 3/8/2015.

Patient N.D. has a foley catheter since 3/4/2015. He is under the

care of Dr. A. He was cared by Nurse Compassion on 3/5/2015.

Patient S.R. has a 2 x 2 bedsore observed since 3/5/2015. He is

under the care of Dr. C. He was cared by Nurse Competence on

3/8/2015. He was also handled by Nurse Compassion on

3/5/2015.


CASE STUDY

Step 6: Develop a

Hypothesis

The tentative hypothesis is that

Klebsiella pneumoniae

carbapenemase infection is being

transmitted from an index case to

other patients in the ICU probably

because of a break in infection

control practices.


CASE STUDY

Step 7: Test the

Hypothesis

The ICU link nurse notes that Nurse

Compassion was involved in 2/4 cases and in

the first case of KPC (patient N.D.)

Nurse Competence was involved in 2/4 cases,

and Nurse Love was involved in 1/4 cases.

Dr. A was involved in 2/4 cases (B.L. and

N.D.)

She decides to determine if their presence

are significant by conducting an audit of their

practices.


CASE STUDY

Step 7: Test

Hypotheses

Audit of Healthcare Worker Practices:

Nurse Competence has a hand hygiene

compliance of 15%.

Nurse Compassion has a hand hygiene

compliance of 50%, but he uses the same gloves

for draining the urinary bag.

Dr. B and A both have a hand hygiene compliance

of 30%.

On 3/10/2015, Patient A.N. was immediately

admitted to the ICU-2 post-OR due to severe

hemodynamic instability. The room has just been

vacated by Patient B.L.


CASE STUDY

Step 7: Test

Hypotheses

Environmental cultures at the

ICU were done to determine the

source of the outbreak.

A culture of the ff. were done:

Bedrails at ICU Beds 2,5,9

Gloves used by Nurse

Compassion for draining urine of

patient N.D.


CASE STUDY

Step 7: Test

Hypotheses

Result of cultures:

Bedrails at ICU Beds 2 & 5 were

positive for KPC

Gloves used by Nurse

Compassion for draining urine of

patient N.D. was positive for KPC


CASE STUDY

Step 8: Refine

Hypotheses and

Draw Conclusions

Patient N.D. with CAUTI 2 to KPC is the

index case (infected March 5, 2015).

Nurse Compassion transmitted KPC from

the urine of Patient N.D. to the wound of

Patient S.R. on March 5, 2015 because she

does not change gloves when draining the

urine bag.

Patient B.L developed VAP 2 to KPC on

March 8, 2015 which was transmitted from

Patient S.R. through the contaminated

hands of Nurse Competence (HHC of

15%).


CASE STUDY

Step 8: Refine

Hypotheses and

Draw Conclusions

The wound of Patient S.R. was infected

with KPC on March 8, 2015 which was

transmitted from patient B.L. through the

contaminated hands of Nurse Competence

(15% Hand hygiene compliance).

Patient A.N. developed VAP 2 to KPC on

March 12, 2015 because of inadequate

environmental cleaning of ICU 2 which was

just vacated by Patient B.L. with VAP 2 to

KPC.


CASE STUDY

Step 9:

Implementing

Control and

Prevention

Measures

The ICU link nurse recommends the

following:

Implement contact precautions for all

patients with KPC HAI and Droplet

Precautions for all patients with VAP 2

to KPC.

Gloves used for draining urine should

be disposed immediately after single

use.

Routine environmental cleaning of all

ICU cubicles should be done.

Nurse Competence and Nurse

Compassion were required to attend

in-service Infection Control seminar.


CASE STUDY

Step 10:

Communicate

Findings

All staff was informed of findings

and the recommendations.

A written summary of findings

was distributed to appropriate staff.

References:

http://www.cdc.national center for chronic disease prevention and health promotion. Outbreak Investigation

http://www.idready.org. Aragon, T., W. Enanoria, A Reingold. Conducting an outbreak investigation in 7 steps. Center for Infectious Disease Preparedness, UC Berkeley School of Public Health.

Outbreak investigation-Case Study by University of Michigan Hospitals and Health Centers, Infection Control & Epidemiology 2002.

http://www.cdc.national/

http://www.idready.org/

Outbreak Investigation

Healthcare

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