1. No category

MMWR Week 14 (April 5 – April 11, 2015)
Report Date: April 14, 2015

A total of 89 mosquito pools have been submitted to North Texas Regional Laboratory (NTRL) at
Tarrant County Public Health (TCPH) in 2015. All pools tested negative for SLEV and WNV.

To date in 2015 there has been 1 imported human DENV case, no CHIKV disease cases, no SLEV
cases, and no WNV cases reported in Tarrant County.

More information can be found at: Tarrant County Mosquito-Borne Illness
CHIKV-Chikungunya Virus; DENV-Dengue Virus; SLEV-St. Louis Encephalitis Virus; WNV–West Nile Virus
Table 1. WNV activity summary, Tarrant County, Weeks 13-14, 2015
Week
Mar 29 Apr 4
Apr 5 Apr 11
MMWR Week
13
14
Total traps placed in Tarrant County
30
56
86
Average number of female Culex species per trap
5.5
41.6
28.7
0
89
89
0
0
0
0
0
0:00
0
0
0
0.00
0.00
0.000
0.000
Number of mosquito pools tested
1
Number of positive mosquito pools (NTRL; Non-NTRL)
Confirmed WNV human cases (WNF; WNND)
3
Presumptive WNV viremic blood donors
WNV infection rate per 1,000 Cx. quinquefasciatus
5
Weekly vector index
1
Based on lab testing date;
2
4
2
YTD
Based on mosquito collection date; NTRL = North Texas Regional Laboratory
3
Based on onset of illness date for cases reported to Tarrant County Public Health; WNF=West Nile Fever;
WNND = West Nile Neuroinvasive Disease
4
Calculated using a Maximum Likelihood Estimation (MLE). Biggerstaff, Brad J. PooledInfRate, Version 4.0: a
Microsoft® Office Excel© Add-In to compute prevalence estimates from pooled samples. Centers for Disease
Control and Prevention, Fort Collins, CO, U.S.A., 2009
5
Vector Index is a measure of infectivity accounting for vector species composition, vector species population
density, and proportion of vector population infected with WNV
Note: Infection rate and vector index calculations do not include positive pools from Non-NTRL laboratories;
Data subject to change due to on-going case investigations, mosquito collection, and testing
Data source: Tarrant County Public Health
Tarrant County Arbovirus Surveillance Update 04/14/15
Figure 1. Average number of female Culex species per trap and vector index, Tarrant County, 2014-2015
1.00
2014 Average
2015 Average
2014 Vector Index
2015 Vector Index
90.0
0.75
60.0
0.50
30.0
0.25
Vector Index
Average female Culex species
120.0
0.00
0.0
13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Collection date by MMWR week
Data source: Tarrant County Public Health
Figure 2. Number of WNV positive mosquito pools by lab testing date, North Texas Regional
Laboratory, 2014-2015
Number of WNV Positive Pools
40.0
2014
2015
30.0
20.0
10.0
0.0
13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Lab testing date by MMWR week
Data source: Tarrant County Public Health
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Tarrant County Arbovirus Surveillance Update 04/14/15
Figure 3. West Nile Virus mosquito trap results, Tarrant County, Week 14, 2015
Map created using the Tarrant County Public Health WNV Interactive
Mapping Tool available at
https://gisit.tarrantcounty.com/WNVCoopPublic/#
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