West Nile Virus Activity in California 2006 Division of Communicable Disease Control California Department of Health Services

West Nile Virus West Nile Virus Activity in Activity in CaliforniaCalifornia

2006 2006

Division of Communicable Disease ControlCalifornia Department of Health Services

http://www.dhs.ca.gov/

WNV in California, 2003

Equine Case (1)

Human Case (3)

32 10,111

70 31,227

96 1,769

POS N

WNV Activity in California WNV Activity in California 20042004

WNV activity (number of human infections)

WNV activity (no human infections)

58 counties15

1

197

116

331

60

7

1

6

3

64

2

2

1

1

10

1 1

3

3

1

1

3

Humans, infections / deaths

Horses, cases / deaths

Dead birds

Mosquito pools

Sentinel chickens

830 / 28

540 / 230

3,232

1,136

805

WNV Activity in California WNV Activity in California 20052005



68

104

177

60

35

25

63

32

47

17

35

365

92

9

281

211

195

12

1

4

1

2

1

4

12

1

1

935 / 19

456 / 200

3,046

1,242

790



Dead birds

Mosquito pools

Sentinel chickens

N = 40 counties with human infection

4

13

1

1

2

1

1

6

0

1 0

2 0

3 0

4 0

5 0

6 0

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 4 0 4 1 4 2 4 3 4 4 4 5

Sequence of WNV detection events in California Sequence of WNV detection events in California relative to human caserelative to human case onset, 2006 onset, 2006

• Birds, mosquitoes: date of collection• Chickens: date of probable seroconversion

Week of onset

Nu

mb

er o

f ca

ses

1/10

4/26

5/3

6/01* 6/28

60

50

40

30

20

10

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

*Estimated Date of Onset

http://www.dhs.ca.gov/

May 26, 2006May 26, 2006

N = 0 counties with human cases

WNV activity (number of human cases with known onset date)

WNV activity (no human cases)

0 / 0

0 / 0

8

19

1

Humans, onset / reported

Horses, onset / reported

Dead birds

Mosquito pools

Sentinel chickens

1

1 1

1

June 30, 2006June 30, 2006




4 / 1

1 / 0

45

22

6



Dead birds

Mosquito pools

Sentinel chickens

1

20

3

3

2

1

11

4

2

1

2

1

1

1

1

1

2

3

1

1

July 28, 2006July 28, 2006




61 / 17

10 / 5

219

184

91



Dead birds

Mosquito pools

Sentinel chickens

1

37

7

8

6

2510

3

9

7

2

4 2

29

7

4

8

1

15

1

5

2

1

1

1

1

1

1

1

2

11

4

2

4

August 29, 2006August 29, 2006




213 / 127

34 / 25

688

575

323



Dead birds

Mosquito pools

Sentinel chickens

1

46

12

10

8

7

2514

4

10

10

2

5 4

31

8

4

8

1

18

2

5

2

4

1

1

1

2

4

5

4

1

1

2

1

1

September 29, 2006September 29, 2006




255 / 251

51 / 49

1,162

794

491

24



Dead birds

Mosquito pools

Sentinel chickens

Squirrels

September 29, 2006September 29, 2006

1

47

12

10

8

8

2515

4

10

10

2

5 4

31

8

4

8

1

18

2

6

2

4

1

1

1

2

5

6

4

1

1

2

1

1

October 31, 2006October 31, 2006




261 / 278

52 / 53

1,340

825

628

32



Dead birds

Mosquito pools

Sentinel chickens

Squirrels

1

51

12

12

8

12

2716

4

12

16

2

5 4

34

8

4

8

1

18

2

6

3

4

1

1

1

2

6

6

7

1

1

3

1

1

WNV Activity in WNV Activity in California, 2006California, 2006

N = 36 counties with human infections



292 / 7

58 / 24

1,446

832

640

32



Dead birds

Mosquito pools

Sentinel chickens

Squirrels

1

Glenn 45.36Colusa 21.27Modoc 21.17

Yolo 16.01 > 15Butte 15.26Sutter 15.2

Tehama 10.71

Yuba 8.30 > 5Mono 7.78Kern 7.41

Lake 3.43Placer 3.22Stanislaus 2.46Shasta 2.45Solano 2.03

Merced 1.90 > 1Tulare 1.63San Joaquin 1.42Fresno 1.38El Dorado 1.28Sacramento 1.23Nevada 1.09

Others > 0

2006 2006 Reported WNV Reported WNV

cases per cases per 100,000 people100,000 people

CA Total 0.82

Human infections 292

Top Five Counties with Human WNV InfectionsTop Five Counties with Human WNV Infections

2005Sacramento 177

Riverside 104

Stanislaus 92

Kern 67

Fresno 63

Kern 51

Butte 34

Yolo 27

Sacramento 16

Los Angeles 16

20062006

Los Angeles 323

San Bernardino 191

Riverside 112

Orange 64

Kern 60

2004

Human Infections 2005-2006Human Infections 2005-2006

Human infections 928 292

Counties 40 36

Positive blood donors 93 28

Symptomatic donors 42 (45%) 14 (50%)

2005 2006

Number of symptomatic cases 873 278

Clinical presentation

Neuroinvasive 301 (36%) 83 (30%)

Fever 524 (64%) 190 (68%)

Unknown 48 5

Median age 51 yrs 49 yrs

Fatal cases 18 7

Median age of fatalities 79 yrs 82 yrs

Human WNV Clinical Presentation Human WNV Clinical Presentation 2005 - 20062005 - 2006

2005 2006

Incidence of WNV illness by age and clinical Incidence of WNV illness by age and clinical presentation, California, 2006presentation, California, 2006

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+

WNF

WNND

Rep

ort

ed i

nci

den

ce p

er 1

00,0

00 p

op

.

Age Group (years)

(n=278)(n=278)

0

1 0

2 0

3 0

4 0

5 0

6 0

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6

WNF

WNND

Unknown

Human WNV Cases in California, 2006Human WNV Cases in California, 2006

Week of onset

Nu

mb

er o

f ca

ses

60

50

40

30

20

10

*Estimated Date of Onset

20-M

ay

3-Ju

n

17-J

un

1-Ju

l

15-J

ul

29-J

ul

12-A

ug

26-A

ug

9-S

ep

23-S

ep

7-O

ct

21-O

ct

4-N

ov

Jun 1 Nov 2

May Jun Jul Aug Sep Oct Nov

• Onset dates not available for all patients

Onset of Human Illness 2005-2006Onset of Human Illness 2005-2006

0

20

40

60

80

100

120

140

160

2004

2005

2006

Nu

mb

er o

f ca

ses

Week of onset

11-M

ar

25-M

ar

8-A

pr

22-A

pr

6-M

ay

20-M

ay

3-Ju

n

17-J

un

1-Ju

l

15-J

ul

29-J

ul

12-A

ug

26-A

ug

9-S

ep

23-S

ep

7-O

ct

21-O

ct

4-N

ov

18-N

ov

Dead Bird SurveillanceDead Bird Surveillance

Dead Bird Surveillance Program Dead Bird Surveillance Program 2000 - 20062000 - 2006

Year Reported Tested Positive

2000 40 20 0

2001 68 18 0

2002 3,666 653 0

2003 8,650 1,765 96

2004 93,057 5,728 3,232

2005 109,375 9,263 3,046

2006 46,345 6,535 1,446

No detected incidence

1 – 19 %

20 – 39 %

40 – 59 %

60 – 79 %

Prevalence of WNV in Tested Prevalence of WNV in Tested Dead Birds*, 2006Dead Birds*, 2006

* Prevalence = (# pos birds / # tested birds) x 100

2006: 87 species of WNV positive dead birds2006: 87 species of WNV positive dead birds

Other Corvids (2 species) 2%

Non-Corvids (82 species) 23%

American Crow 47%

Western Scrub Jay 21%

Yellow-billed Magpie 7%

Number reported = 46,345

Number tested = 6,535

Number WNV pos = 1,446

0

5

10

15

20

25

30

Apr May Jun Jul Aug Sep Oct Nov

House Finch

American Robin

House Sparrow

Northern Mockingbird

Barn Owl

Cooper's Hawk

Top 6 WNV Positive Non-Corvids, 2006Top 6 WNV Positive Non-Corvids, 2006

2006

WNV Positive Corvids and Non-Corvids WNV Positive Corvids and Non-Corvids January-AprilJanuary-April

2005

Non-corvids 33%

Corvids 67%Non-Corvids 73%

Corvids 27%

DYCAST 2006DYCAST 2006• DYCAST is a statistical model that was used to

identify clustering of dead bird reports temporally and spatially

• Correlation between dead bird reports per capita and human cases– The more reports made, the more likely that DYCAST

identified increased WNV activity where human cases subsequently occurred

• DYCAST was used by most of the local agencies to assist them in directing mosquito larviciding and adulticiding in 2006

First positive squirrel: August 1, 2006

Prevalence (PCR): 23.2% (32/138)

• nine counties with positive tree squirrels

Similar to prevalence in dead birds (22.1%)

WNV in California WNV in California Tree Squirrels - 2006Tree Squirrels - 2006

WNV Activity in Mosquitoes WNV Activity in Mosquitoes

0

20

40

60

80

100

120

140

160

4/2

0

5/4

5/1

8

6/1

6/1

5

6/2

9

7/1

3

7/2

7

8/1

0

8/2

4

9/7

9/2

1

10

/5

10

/19

11

/2

11

/16

11

/30

12

/14

Date

Posi

tive

Po

ols

20052006

WNV Activity in Mosquitoes WNV Activity in Mosquitoes number positive poolsnumber positive pools

2006: 832 / 25,613

2005: 1,242 / 21,402

WNV Positive Mosquito SpeciesWNV Positive Mosquito Species832 positive pools

Culextarsalis 430 (52%)quinquefasciatus 266 (32%)pipiens 119 (14%)stigmatosoma 6 (<1%)erythrothorax 7 (<1%)

Culiseta incidens 1 (<1%)Anopheles freeborni 1 (<1%)Aedes melanimon 2 (<1%)

0.21

1.48

2.79

1.81

1.86

0 0.5 1 1.5 2 2.5 3

Cx. erythrothorax

Cx. tarsalis

Cx. pipiens

Cx. quinquefasciatus

Cx. stigmatosoma 231 pools tested

2,698 pools tested

3,560 pools tested

6,531 pools tested

670 pools tested

Minimum Infection Rate (MIR)*

* MIR = (# positive mosquito pools / total number of mosquitoes tested) X 1,000

Minimum Infection Rates (per 1,000) by Species Minimum Infection Rates (per 1,000) by Species July – September 2006July – September 2006

Minimum Minimum Infection Rate Infection Rate

(MIR)* (MIR)*

Counties Counties Submitting Submitting Mosquitoes Mosquitoes

20062006

* MIR = (# positive mosquito pools/total number of mosquitoes tested) X 1,000

Includes Culex mosquitoes only

YubaLassenEl dorado

CalaverasKernSanta ClaraSutterKingsFresnoPlacer

ShastaMaderaTulareVenturaYoloStanislausLos AngelesImperialButte

LakeMarinInyoSacramentoSan BernardinoSan JoaquinGlennAlamedaContra CostaMercedSolanoOrangeSonomaRiverside

Santa Barbara

No positive poolsNo mosquitoes tested

6. 75.84.8

3.83.33.22.82.32.22.0

1.91.71.51.31.31.11.11.01.0

0.90.80.80.80.80.70.70.60.50.50.50.40.20.2

0.07

0

> 4.0

> 2.0

> 1.0

> 0.1

WNV Activity in WNV Activity in Sentinel ChickensSentinel Chickens

Negative flock

WNV positive flock

Sentinel Chicken Sentinel Chicken Surveillance Program Surveillance Program

20062006

• 640 seroconversions• 29 counties• 122 / 245 flocks

WNV Activity in Sentinel WNV Activity in Sentinel ChickensChickens

0

20

40

60

80

100

120

140

160

5/4

5/18 6/1

6/15

6/29

7/13

7/27

8/10

8/24 9/7

9/21

10/5

10/1

9

11/2

11/1

6

11/3

0

12/1

4

12/2

8

Date

Pos

itive

Chi

cken

s 20052006

2005 790 pos (141 / 253 flocks)2006 640 pos (122 / 245 flocks)

Equine WNV Equine WNV SurveillanceSurveillance

20062006

58 cases 622 tested

(23 positive counties)

2005: 456 cases

http://www.cdfa.ca.gov/

2006 Equine WNV Cases2006 Equine WNV Cases•58 WNV infected horses (23 counties)•24 (41%) died / euthanized•Vaccination status

• 5 properly vaccinated• 2 improperly vaccinated• 44 non-vaccinated

•Median age: 11 years (1 – 34 years)

0

2

4

6

8

101-

Jul

15-J

ul

29-J

ul

12-A

ug

26-A

ug

9-S

ep

23-S

ep

7-O

ct

21-O

ct

4-N

ov

18-N

ov

2-D

ec

16-D

ec

Nu

mb

er o

f ca

ses

Week of onset

Week of Onset for Equine WNV CasesWeek of Onset for Equine WNV CasesCalifornia, 2006California, 2006

Jun 26

Dec 10

VBDS Vicki Kramer Stan Husted Ryan Carney Kerry Padgett Tina Feiszli Colleen Barclay Anne Kjemtrup Jamie Riggs-Nagy Rachel Owens Mark Novak Renjie Hu Hotline staff Regional biologists

DIS Jon Rosenberg

VPHS Ben Sun James Glover Claudia Erickson

VRDL Carol Glaser Cynthia Jean Cindi Cossen Liz Baylis Shilpa Jani

OPA Michele Mussuto

WNV Team at DHSWNV Team at DHS

Local Health Departments

Local Public Health Laboratories

Environmental Health Departments

CollaboratorsCollaborators

http://mvcac.org/

http://vector.ucdavis.edu/surveillance/default.html

http://www.cdfa.ca.gov/

Documents

West Nile Virus Activity in California 2006 Division of Communicable Disease Control California Department of Health Services