www.cdc.gov/flu

Daniel B. Jernigan, MD MPHDaniel B. Jernigan, MD MPHDeputy Director, Influenza DivisionDeputy Director, Influenza Division

National Center for Immunization and Respiratory DiseasesNational Center for Immunization and Respiratory Diseases

Surveillance in a Pandemic:Surveillance in a Pandemic:Situational Awareness Situational Awareness and Assessing Severityand Assessing Severity

www.cdc.gov/flu

Objectives

Describe the US experience with surveillance and situational awareness during the 2009 pandemic

Identify some things that worked and some that could be improved

Describe the challenges of measuring severity in an emerging pandemic

www.cdc.gov/flu

First Cases Prompt

Investigation April 21 report of two cases in Southern California Both cases seen as outpatients, both recovered April 24 report of link with cases in Mexico

Same virus, different sense of “severity” or potential impact

Cases prompted a cascade of activity Enhanced surveillance Virus characterization

MMWR

www.cdc.gov/flu

CDC Virologic Surveillance in the First Week

0

2000

4000

6000

8000

10000

12000

Week Number

Num

ber

of

Posi

tive S

peci

mens

0

10

20

30

40

50

60

70

80

90

100

Perc

ent

Posi

tive

B A(Subtyping not performed) A(H1)

A(H3) A(Unable to Subtype) A(2009 H1N1)

Percent Positive

2008 2009

35,000Specimens Tested in One Week

196,000Specimens

Tested Over the Season

www.cdc.gov/flu

April 27CDC posts 40 gene

sequences on

GenBank

May 1First Diagnostic Kits Shipped toWHO Network and State Labs

To date: 2,125 kits to 432 labs in 142 Countries

May 7Case Series (N=642)

Published in NEJM

May 23Vaccine Strain

Begins Shipping toManufacturers

April 28CDC Posted PCR

Protocol on

WHO website

Virus

DetectedField Investigations and Enhanced Surveillance

Early Assessment

www.cdc.gov/flu

Early Estimate of Symptomatic Case Fatality RatioReed, Biggerstaff – CDC unpublished data

www.cdc.gov/flu

Making Situational Awareness Possible in the First Days

Early communication accelerated global response

Case-contact investigations and community surveys were critical for early characterization

Availability of diagnostics aided response PCR devices in place or quickly deployed Influenza Reagent Resource for distribution

Preparedness investments invaluable

www.cdc.gov/flu

Early Challenges Decisions need to be made on limited data

Estimating and monitoring impact is an ongoing process

Need to manage expectations of stakeholders and decision-makers

Pandemic planning called for severity estimates based on mortality alone; however, may not be available may not reflect the potential impact of the pandemic are difficult to maintain with lab-confirmation

www.cdc.gov/flu

Pandemic Severity Index Benchmarked to Past Pandemic Mortality

www.cdc.gov/flu

During the Summer

www.cdc.gov/flu

CDC Virologic Surveillance During the Summer Months

0

2000

4000

6000

8000

10000

12000

Week Number

Num

ber

of

Posi

tive S

peci

mens

0

10

20

30

40

50

60

70

80

90

100

Perc

ent

Posi

tive

B A(Subtyping not performed) A(H1)

A(H3) A(Unable to Subtype) A(2009 H1N1)

Percent Positive

2008 2009

ILI visits greatly increased above baseline Notably in younger patients

Hospitalization rates point to increases in younger patients

PCR-confirmed case counting stopped

www.cdc.gov/flu

On Arrival at CampCabin has 25 Campers

Situational Awareness from CampersA Personal Account

www.cdc.gov/flu

On Arrival at CampCabin has 25 Campers

One Week LaterCabin has 11 Campers

Situational Awareness from CampersA Personal Account

www.cdc.gov/flu

Observations from the Summer Existing laboratory and epidemiologic infrastructure

critical for sustained surge New surveillance activities initiated

Aggregate hospitalization and deaths reporting Reports from electronic health records

Serologic studies helpful for indicating immunity in older individuals need more automated and rapid testing capacity

Uncertainty of potential changes in the virus required maintained vigilance and planning

www.cdc.gov/flu

Through the Fall Wave

www.cdc.gov/flu

0

2000

4000

6000

8000

10000

12000

Week Number

Num

ber

of

Posi

tive S

peci

mens

0

10

20

30

40

50

60

70

80

90

100

Perc

ent

Posi

tive

B A(Subtyping not performed) A(H1)

A(H3) A(Unable to Subtype) A(2009 H1N1)

Percent Positive

2008 2009

CDC Virologic Surveillance through the Fall Wave

www.cdc.gov/flu

Clinics & ED’s

Hospital

Death

Assessing “severity” or “influenza impact” was accomplished using surveillance data to monitor morbidity and

mortality to compare with prior

seasons to estimate numbers of

cases

www.cdc.gov/flu

Visits for ILI surpassed prior seasons, notably among younger age groups

0

1

2

3

4

5

6

7

8

9

10/7

/06

12/2

/06

1/27

/07

3/24

/07

5/19

/07

7/14

/07

9/8/

07

11/3

/07

12/2

9/07

2/23

/08

4/19

/08

6/14

/08

8/9/

08

10/4

/08

11/2

9/08

1/24

/09

3/21

/09

5/16

/09

7/11

/09

9/5/

09

10/3

1/09

12/2

6/09

2/20

/10

4/17

/10

6/12

/10

8/7/

10

Week

% o

f V

isits

for

ILI

% ILI National Baseline

2006-07

2007-08

2008-09

2009-10

Schools Start

www.cdc.gov/flu

2009 H1N1 Hospitalizations varied by age and differed from previous seasons

CDC Emerging Infections Program

* Pan H1N1 is for data from Sep 1, 2009 to Jan 21, 2010

www.cdc.gov/flu

Pneumonia and Influenza Mortality for 122 U.S. CitiesAggregate data does not represent impact on those <65

4

6

8

10

50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20

Weeks

% o

f A

ll D

eath

s D

ue t

o P

&I

2006-07 2007-08 2008-09 2009-102005-06

FallWave

H3N2

www.cdc.gov/flu

Number of Influenza-Associated Laboratory-Confirmed Pediatric Deaths

0

5

10

15

20

25

30

35

2007-4

0

2007-4

6

2007-5

2

2008-0

6

2008-1

2

2008-1

8

2008-2

4

2008-3

0

2008-3

6

2008-4

2

2008-4

8

2009-0

1

2009-0

7

2009-1

3

2009-1

9

2009-2

5

2009-3

1

2009-3

7

2009-4

3

2009-4

9

2010-0

3

Week of Death

Nu

mb

er

of

de

ath

s

2007-08

88 Pediatric Deaths

2008-09

69 Pediatric Deaths

www.cdc.gov/flu

Number of Influenza-Associated Laboratory-Confirmed Pediatric Deaths

0

5

10

15

20

25

30

35

20

07

-40

20

07

-46

20

07

-52

20

08

-06

20

08

-12

20

08

-18

20

08

-24

20

08

-30

20

08

-36

20

08

-42

20

08

-48

20

09

-01

20

09

-07

20

09

-13

20

09

-19

20

09

-25

20

09

-31

20

09

-37

20

09

-43

20

09

-49

20

10

-03

Week of Death

Nu

mb

er

of

de

ath

s

2007-08

88 Pediatric Deaths

2008-09

69 Pediatric Deaths

Since H1N1

344 Pediatric Deaths

4 – 5 times more than

prior seasons

www.cdc.gov/flu

Characteristics of 2009 H1N1 InfluenzaApril 15, 2009 to April 10, 2010

Cases61,000,000 (43M – 89M)

Hospitalizations274,000 (195K – 403K)

Deaths12,470 (8.9K – 19.3K)

0-4

5-24

25-4

9

50-6

4

≥65

App

roxi

mat

e R

ate

per

100,

000

popu

latio

n

www.cdc.gov/flu

Assessing Severity Assessments

Mortality alone does not reflect the full pandemic impact 90% of deaths generally among >65 yos For H1N1, 90% among <65 yos Lab-confirmed cases underreported Estimates of years of potential life lost range

334K to 1.2M (Viboud PLoS Curr Influenza 2010)

Many difficult decisions need to be made early when limited data may be available

www.cdc.gov/flu

Next Steps for Severity Assessment

Efforts underway at WHO to identify new approach to severity assessment

CDC gathering input on a new framework drafted by Reed and Biggerstaff which allows for: Data collection from early virologic and field

investigations, as well as established systems Assesment based on categories of transmission and

clinical severity Translation of the findings into context- appropriate

recommendations

www.cdc.gov/flu

Thank You

Acknowledgements State and Local Health Departments WHO and numerous international public health

partners CDC

Influenza Division Epidemiology and Laboratory Branches

Staff and guests assisting in the response