U.S. Influenza Surveillance2004 - 2005

Keiji Fukuda

Influenza Branch

National Center for Infectious Diseases

Centers for Disease Control and Prevention

Evolving U.S. Influenza Surveillance

Core• Viruses

– WHO / NRVESS Laboratory System

• Influenza-like illness– Sentinel Provider (SP)

System• Mortality

– 122 cities – NCHS

• State activity assessment– State & Territorial

Epidemiologists Report

Changes Underway• Current systems

– Enhancements to SP system• New Systems Added

– Pediatric influenza hospitalizations

• New Vaccine Surveillance Network

• Emerging Infections Program

– Pediatric influenza deaths– H5N1 detection in ill

travelers• Under evaluation

– Biosense– Notifiable diseases, etc.

Growth of the Influenza Sentinel Physician Surveillance System

0

500

1000

1500

2000

2500

1996-97 1997-98 1998-99 1999-2000 2000-01 2001-02 2002-03 2003-04 2004-05*

Season

En

roll

ed P

hys

icia

ns

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

10000000

Pat

ien

t vi

sits

enrolled physicians regularly reporting physicians patient visits

* Data as of 1/27/2005

Sentinel Provider System Coverage Map

Visits for Influenza-like Illness to U.S. Sentinel Providers, 2002 - 2005

0

1

2

3

4

5

6

7

8

9

10

40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20

Week

% o

f V

isit

s f

or

ILI

%ILI 2004-05 % ILI 2003-04 %ILI 2002-03 national baseline

2004 – 2005 U.S. Season

Influenza Virus Detections, 2004-05 U.S. WHO/NREVSS Collaborating Laboratories

58,286Negative

1,041 (14.6%)Influenza B

1986 (32.7%) subtyped

6 (0.3%)H1 1980 (99.7%)

H3N2

65,404 specimens tested for influenza viruses

7,118 (10.9%) Positive

6,077 (85.4%) influenza A

U.S. WHO/NREVSS Collaborating LaboratoriesSummary, 2004-05

0

200

400

600

800

1000

1200

1400

40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20

Week

Nu

mb

er

of

Iso

late

s

0

5

10

15

20

25

30

Pe

rce

nt

Po

sit

ive

A(H3N2)

A(H1N1) and A(H1N2)

A(Unsubtyped)

B

Percent Positive

Visits for Influenza-like Illness to U.S. Sentinel Providers, 2002 - 2005

0

1

2

3

4

5

6

7

8

9

10

40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20

Week

% o

f V

isit

s f

or

ILI

%ILI 2004-05 % ILI 2003-04 %ILI 2002-03 national baseline

NVSN Influenza (Lab Confirmed) Hospitalization RatesChildren 0 - 4 Years, 2000 - 2005

0

2

4

6

8

10

12

14

40-41 42-43 44-45 46-47 48-49 50-51 52 -1 2-3 4-5 6-7 8-9 10-11 12-13 14-15 16-17 18-19

2004-05 Influenza Season 2 Week Reporting Period

Po

pu

lati

on

-Bas

ed R

ate

per

10,

000

Ch

ildre

n

2000-2001 2001-2002 2002-2003 2003-2004 2004-2005

This graph has been updated from the January 21, 2004 report due to laboratory confirmation of an additional influenza hospitalization between December 26, 2004 and January 8, 2005.

EIP Influenza (Lab Confirmed) Hospitalization RatesChildren 0-4 years & 5-17 years, 2003 - 2005

0

2

4

6

8

10

12

14

40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

2004-2005 Reporting Weeks

Pop

ulat

ion-

Bas

ed R

ate

per

10,0

00 C

hild

ren

Cumulative Rate for 0-4 years, 2003-2004 Cumulative Rate for 5-17 years, 2003-2004

Cumulative Rate for 0-4 years, 2004-2005 Cumulative Rate for 5-17 years, 2004-2005

4

6

8

10

12

Weeks

% o

f All

Dea

ths

Due

to P

&I

2001 2002 2003

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

Epidemic Threshold

Seasonal Baseline

Pneumonia and Influenza Mortalityfor 122 U.S. CitiesWeek Ending 2/05/2005

2004

Weekly Influenza Activity Estimates Reportedby State & Territorial Epidemiologists

Week ending February 05, 2005 - Week 5

No Report Sporadic Regional Widespread No Activity Local Activity

Conclusion

• Moderate impact compared with 2003

• Dominated by A (H3N2) viruses

• 6 reported pediatric deaths

• Ongoing activity