West Nile Virus Activity in California 2006
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West Nile Virus West Nile Virus Activity in Activity in CaliforniaCalifornia
2006 2006
Division of Communicable Disease ControlCalifornia Department of Health Services
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WNV in California, 2003
Equine Case (1)
Human Case (3)
32 10,111
70 31,227
96 1,769
POS N
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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
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WNV Activity in California WNV Activity in California 20052005
WNV activity (number of human infections)
WNV activity (no human infections)
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
Humans, infections / deaths
Horses, cases / deaths
Dead birds
Mosquito pools
Sentinel chickens
N = 40 counties with human infection
4
13
1
1
2
1
1
6
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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
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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
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1
1 1
1
June 30, 2006June 30, 2006
N = 4 counties with human cases
WNV activity (number of human cases with known onset date)
WNV activity (no human cases)
4 / 1
1 / 0
45
22
6
Humans, onset / reported
Horses, onset / reported
Dead birds
Mosquito pools
Sentinel chickens
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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
N = 19 counties with human cases
WNV activity (number of human cases with known onset date)
WNV activity (no human cases)
61 / 17
10 / 5
219
184
91
Humans, onset / reported
Horses, onset / reported
Dead birds
Mosquito pools
Sentinel chickens
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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
N = 34 counties with human cases
WNV activity (number of human cases with known onset date)
WNV activity (no human cases)
213 / 127
34 / 25
688
575
323
Humans, onset / reported
Horses, onset / reported
Dead birds
Mosquito pools
Sentinel chickens
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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
N = 36 counties with human cases
WNV activity (number of human cases with known onset date)
WNV activity (no human cases)
255 / 251
51 / 49
1,162
794
491
24
Humans, onset / reported
Horses, onset / reported
Dead birds
Mosquito pools
Sentinel chickens
Squirrels
September 29, 2006September 29, 2006
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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
N = 36 counties with human cases
WNV activity (number of human cases with known onset date)
WNV activity (no human cases)
261 / 278
52 / 53
1,340
825
628
32
Humans, onset / reported
Horses, onset / reported
Dead birds
Mosquito pools
Sentinel chickens
Squirrels
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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
WNV activity (number of human infections)
WNV activity (no human infections)
292 / 7
58 / 24
1,446
832
640
32
Humans, infections / deaths
Horses, cases / deaths
Dead birds
Mosquito pools
Sentinel chickens
Squirrels
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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
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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
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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
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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
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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)
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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
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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
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Dead Bird SurveillanceDead Bird Surveillance
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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
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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
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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
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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
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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%
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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
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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
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WNV Activity in Mosquitoes WNV Activity in Mosquitoes
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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
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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%)
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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
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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
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WNV Activity in WNV Activity in Sentinel ChickensSentinel Chickens
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Negative flock
WNV positive flock
Sentinel Chicken Sentinel Chicken Surveillance Program Surveillance Program
20062006
• 640 seroconversions• 29 counties• 122 / 245 flocks
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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)
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Equine WNV Equine WNV SurveillanceSurveillance
20062006
58 cases 622 tested
(23 positive counties)
2005: 456 cases
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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)
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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
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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
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Local Health Departments
Local Public Health Laboratories
Environmental Health Departments
CollaboratorsCollaborators