West Nile Virus in Tarrant County, Texas...West Nile Virus 2012 Data Tarrant County Public Health...

Tarrant County Public Health North Texas Regional Laboratory

West Nile Virus in Tarrant County, Texas

Guy C. Dixon, Ph.D.


Tarrant County WNV Geographical Information

2003 - 2012


3

Tarrant County WNV Geography


4



5



6



7



West Nile Virus 2012 Data


9

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 (%)


10

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 WNV Trends

2003 – 2012


12


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


13

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


14


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


15

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


16


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2004

Average 2003-2012


17


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2005

Average 2003-2012


18


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2006

Average 2003-2012


19


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2007

Average 2003-2012


20


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2008

Average 2003-2012


21


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2009

Average 2003-2012


22


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2010

Average 2003-2012


23


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2011

Average 2003-2012


24


(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%


Month

Rat

io o

f WN

V P

ositi

ve P

ools

2012

Average 2003-2012

October data as of 10/26/2012


25


(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%


Month

Rat

io o

f WN

V Po

sitiv

e Po

ols

2003

2006

2012

Average 2003-2012


26

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)


27

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


28

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


29

Acknowledgements

• Michelle Markham, Environmental Health - GIS

• Kaylene Thomason, Environmental Health • Dr. Anita Kurian, Epidemiology • Dr. Rune-Par Nilsson, BREA Lab Section

Supervisor

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