Fort Worth Still Without West Nile Positive Mosquitoes - NBC 5 Dallas-Fort Worth

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Fort Worth Still Without West Nile Positive Mosquitoes

Scientists cannot say why this trend is happening



    The West Nile virus seems to be targeting Tarrant County, but not Fort Worth so far this year. (Published Wednesday, Aug. 20, 2014)

    In Tarrant County, the West Nile virus seems to be targeting areas outside of Fort Worth.

    So far in 2014, the Tarrant County Public Health Department's interactive mapping software shows 41 positive mosquito traps. But, not one of those positives has been in the county's largest city.

    A vast majority of the positives have been found in northeastern Tarrant County, which those studying and collecting data said is pretty typical.

    Dr. Joon Lee is an assistant professor at The University of North Texas Health Science Center. He and his students collect and test mosquito samples for the city each week.

    Their findings lately show an average of about 50 culex mosquitoes per trap, which he said is high for August.

    "Even though we have high mosquito numbers, we don't seem to have any evidence of West Nile virus transmission at all this year," Lee said.

    So far, the 42 to 62 traps they put out each week haven't caught a single positive mosquito. Last year though, the city saw just five such positive mosquito pools.

    With only two years of intense, thorough and consistent trapping and testing, it remains hard to say why. The mitigation efforts, removing source pools and mosquito breeding grounds, could play a role, so, too, could the 2012 outbreak of the virus.

    "So a lot of local birds might be immunized by the West Nile virus infection," Lee said.

    But Lee said he really needs another three to four years of data to figure out the virus' patterns. That means this season is a bit different than previous years.

    "It is quite interesting to answer all those questions, but still remains to be answered," Lee said.

    One thing Lee knows for sure is that the our rainy days this summer have thrown off the season and is why we're seeing high mosquito numbers once again.

    But more mosquitoes doesn't necessarily mean more risk of West Nile virus.

    Still, Lee said you should continue to take precautions.

    "I would still recommend them to be cautious about that," he said.

    Another unique aspect of this year's season, Tarrant County right now has more positive traps than Dallas County. Historically, it's usually been the other way around. 

    Lee said just because we haven't seen West Nile virus in Fort Worth so far, doesn't mean it won't show up. He said the summer rains could push the season into September and even early October.

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