Tarrant County Public Health North Texas Regional Laboratory West Nile Virus in Tarrant County, Texas Guy C. Dixon, Ph.D.
Tarrant County Public Health North Texas Regional Laboratory
West Nile Virus in Tarrant County, Texas
Guy C. Dixon, Ph.D.
Tarrant County Public Health North Texas Regional Laboratory
Tarrant County WNV Geographical Information
2003 - 2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Geography
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Geography
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Geography
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Geography
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Geography
Tarrant County Public Health North Texas Regional Laboratory
West Nile Virus 2012 Data
Tarrant County Public Health North Texas Regional Laboratory
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WNV Mosquito Pool Testing 2012 WNV Trends
0
10
20
30
40
50
60
70
6/4/2012
6/11/2012
6/18/2012
6/25/2012
7/2/2012
7/9/2012
7/16/2012
7/23/2012
7/30/2012
8/6/2012
8/13/2012
8/20/2012
8/27/2012
9/3/2012
9/10/2012
9/17/2012
9/24/2012
10/1/20
12
10/8/20
12
10/15/2012
10/22/2012
10/29/2012
Date
Num
bers
Submissions
Positives
Positive Ratio (%)
Tarrant County Public Health North Texas Regional Laboratory
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Number of WNV Cases by Onset of Illness, Tarrant County, 2012
0
2
4
6
8
10
12
14
Nu
mb
er
of
WN
V I
lln
essn
es
Onset of Illness Date
West Nile Neuroinvasive Disease
West Nile Fever
Total Number of Cases = 275
Data source: Tarrant County Public Health
Average time
from when a
person
becomes
ill until the
case is
reported
to TCPH is
currently
15.6 days.
Therefore,
illnesses that
began during
this time may
not yet be
reported.
Tarrant County Public Health North Texas Regional Laboratory
Tarrant County WNV Trends
2003 – 2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends
5 225
2353
22 14 320 2
275
1 0 0 0 7 0 0 3 0 011
0
100
200
300
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Year
WNV Human Cases
Deaths Total Cases
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends Mosquito Submissions 2003-2012
636
553
483
338
88
647
137
378
115
227223
99
00
307
2839
61
21
0
100
200
300
400
500
600
700
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Year
# of
Sub
mitt
ed a
nd P
ositi
ve M
osqu
ito P
ools
Submissions
Positives
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends
May
June
July
Aug
ust
Sep
tem
ber
Oct
ober
Nov
embe
r
2012
2010
2008
2006
2004
0
5
10
15
20
25
30
35
40
45
50
# of Positives
Month
Year
Monthly WNV Positives 2003-2012
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2003 and 2003-2012 Average)
11%
30%31%
42%
5%
0%
5%
0%2%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2003
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2004 and 2003-2012 Average)
0.6%
8%4%
9%
1%0%
5%
0%2%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2004
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2005 and 2003-2012 Average)
2.5%
11%
25%
18%
3.2%0%
5%
0%2%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2005
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2006 and 2003-2012 Average)
0%
1.8%
1.5%
30%
6%8.8%
0%5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2006
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2007 and 2003-2012 Average)
0%
7%5%
19%
1%0%
5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2007
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
20
Tarrant County WNV Trends WNV Positive Pools by Month
(2008 and 2003-2012 Average)
0%
6%3%
7%
0%0%
5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2008
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2009 and 2003-2012 Average)
0%
12%
20%
25%
4%0%
5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2009
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2010 and 2003-2012 Average)
0%0%0% 0%0%0%
5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2010
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2011 and 2003-2012 Average)
0%0%0%0%0%
5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2011
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2012 and 2003-2012 Average)
1.2%2.5%
44%
16%
28%
0%
5%
0%1.7%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
May June July August September October November
Month
Rat
io o
f WN
V P
ositi
ve P
ools
2012
Average 2003-2012
October data as of 10/26/2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends WNV Positive Pools by Month
(2003, 2006, 2012, and 2003-2012 Average)
11%
0% 0%
16%
30%31%
42%
6%9%
30%
2%
44%
28%
1%
2%0%
5%0%
2%
8%
14%
18%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
May June July August September October November
Month
Rat
io o
f WN
V Po
sitiv
e Po
ols
2003
2006
2012
Average 2003-2012
Tarrant County Public Health North Texas Regional Laboratory
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Tarrant County WNV Trends Temperature (Mar-May)
67.3
68.6
66.2
70.9
67.1 67.166.2
67.1
69.3
71.6
62
64
66
68
70
72
74
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Year
Deg
ree F
are
nh
eit
Spring Ave Temp Ave (1948-2012)
Tarrant County Public Health North Texas Regional Laboratory
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Conclusions
• A cyclical pattern of increased mosquito to human WNV transmission is emerging
• Weather conditions such as abnormally high spring temperatures may contribute to increased WNV transmission
Tarrant County Public Health North Texas Regional Laboratory
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Future Opportunities
• Develop thresholds for response activities to mitigate WNV transmission to humans
• Research using climatological and additional vector/host information to enhance predictive models for WNV mosquito to human transmission
• Develop efficient and effective surveillance practices for detecting WNV in the environment
Tarrant County Public Health North Texas Regional Laboratory
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Acknowledgements
• Michelle Markham, Environmental Health - GIS
• Kaylene Thomason, Environmental Health • Dr. Anita Kurian, Epidemiology • Dr. Rune-Par Nilsson, BREA Lab Section
Supervisor