Tarrant County Disputes Report Questioning WNV Numbers - NBC 5 Dallas-Fort Worth

Complete coverage of the West Nile virus in North Texas

Tarrant County Disputes Report Questioning WNV Numbers

Report suggests county has more West Nile virus cases than confirmed



    Tarrant West Nile Numbers Questioned

    A new report published in Dallas called Tarrant County numbers of West Nile virus into question -- but Tarrant County Public Health says those estimated numbers in the report aren't accurate. (Published Wednesday, Oct. 10, 2012)

    Tarrant County health officials are disagreeing with a Dallas County report that suggests that Tarrant County's number of West Nile virus cases are underreported.

    The report suggests that the total numbers could be higher than in Dallas County, which experts believe was the epicenter of the outbreak.

    In the analysis by Dallas County Health and Human Services, which was reported by the Dallas Morning News, epidemiologists looked at blood donors that tested positive for West Nile virus. The data and story suggests that Tarrant County should have two to three times the number of neuroinvasive cases of the virus as it currently does.

    On Wednesday, Tarrant County Public Health reported 270 confirmed human cases and nine deaths. Of those 270, 98 were the West Nile neuroinvasive disease.

    But Tarrant County Public Health Medical Director Dr. Sandra Parker disagreed that the number of cases should be higher and that the numbers are underreported.

    "Tarrant County did not underreport the number of West Nile neuroinvasive disease because our numbers are based on actual reports and not on estimates," she said.

    Parker said the formula for the DCHHS study comes from a 2006 Centers for Disease Control and Prevention study that looks at the value of positive cases in the blood donor pool.

    Parker pointed out that the study has limitations. In fact, the CDC report clearly says it has limitations.

    In its conclusion, the study says there are two valuable public health applications -- that it can be an early indicator of a human epidemic and a surveillance tool. (Click here to read the report.)

    Parker equated the estimates generated by the study and formula to that of forecasting the weather.

    "A lot of our local meteorologists are excellent at what they do, but they're not always correct, either, so this is a study that says, 'Hey, this is what you'd expect to see.' But we didn't see it," she said. "But I don't believe we didn't see it because of any fault of Tarrant County physicians or on Tarrant County Public Health reporting the correct information."

    Parker said 90 percent of neuroinvasive cases required hospitalization and 40 percent required intensive care unit treatment. While cases could have been missed, it's highly unlikely, she said.

    "Physicians don't live in a bubble, so they knew there was a West Nile outbreak," Parker said.

    Parker said Tarrant County Public Health used the numbers of actual cases to determine the best way to fight the virus and protect the public.

    More studies are expected to take place as experts examine how to improve efforts and how they might be able to see an outbreak before it hits.

    In this case, though, Parker said the study is simply estimating the possible number of cases. The only way to determine the numbers of an outbreak are to look at the number of reported cases, she said.

    Dallas County Health did not return NBC 5's calls about its study.

    West Nile Virus:
    Click here for complete coverage of the outbreak of West Nile virus in North Texas. Find updated numbers of human cases, spraying schedules, and more FAQs about the disease.