The cost for acute medical care and lost productivity related to the Texas outbreak of West Nile virus in 2012 likely exceeded $47 million, according to a new study released Wednesday.The state’s 1,886 cases demonstrated the need for ongoing mosquito surveillance and the necessity of developing an effective vaccine, said Dr. Kristy Murray, who led the research conducted by the National School of Tropical Medicine at Baylor College of Medicine in Houston.“When you look at what it is costing us as a society, it’s enormous. Last year it was easily $47 million for just acute medical care, and that’s a very, very conservative estimate,” Murray said.That figure doesn’t include include the public health expense of mosquito control. Researchers noted that a recent study showed that the cost of aerial spraying in Dallas County alone exceeded $1.6 million.Longer-term medical costs are likely to be substantial because some of those affected will need continuing rehabilitation and may be disabled, as well as the possible risk of chronic kidney disease, Murray said.Researchers also observed a three-year pattern of increases in reported human cases in Texas.“We may be going into a cycle where we see an even larger outbreak every 10 years,” Murray said. The 2012 outbreak in Texas was more than two times the previous high, which occurred in 2003 with 735 cases, she said.When comparing 2012 cases with the previous 10 years of data, researchers found no difference in the severity of the disease with regard to age.Researchers did find that older adults, minorities, and males were at highest risk for developing the severe form of the disease, which happens when the virus invades the nervous system.Texas at epicenterIn 2012, Texas was the epicenter of the largest West Nile outbreak in U.S. history with 1,868 cases reported and 89 deaths, according to the Texas Department of State Health Services. Nationally, there were a record 5,387 cases and 243 deaths in 2012, according to the U.S. Centers for Disease Control and Prevention.Of the 254 counties in Texas, 135 reported at least one West Nile case, and the overall incidence rate for the state was 7.8 cases per 100,000 population, the study said.Nearly half of the cases (48 percent) were reported in North Texas counties: 259 in Tarrant (14 percent), 396 in Dallas (21 percent), 183 in Denton (10 percent) and 64 in Collin (3 percent), according to the study. Those four counties had a combined incidence rate of 16 cases per 100,000 population.The outbreak peaked in mid-August with 225 reported cases, which is historically the time all prior outbreaks of West Nile in Texas from 2002 to 2011 peaked, the study said.Tarrant County responseIn response to the 2012 outbreak, Tarrant County expects to spend an additional $500,000 over two years to combat the virus, according to County Administrator G.K. Manius. This year, the county started its mosquito surveillance program a month earlier than in the past and added 150 fixed-location mosquito traps. Another 50 mobile traps were utilized to respond to field operations and citizen complaints, said Dr. Anita Kurian, associate director for the Tarrant County Health Department.In 2012, county health officials relied on 30 to 50 mobile trapping units.“The difference this year is that it’s pretty systematic sampling. In the past, traps were haphazardly placed and haphazardly sampled. It’s important to check the traps week after week to give us an idea of what exactly is happening,” Kurian said.“The data we are collecting [are] more valid and more reliable. We can identify hot spots and that enables us to focus our prevention efforts.”This year, the county has recorded 21 positive mosquito samples compared with 84 in 2012, she said. There have been only two human West Nile cases in Tarrant County, one in Fort Worth and one in Keller. In the meantime, additional work needs to be done to develop predictive models for West Nile virus, Murray said, noting that the 2011 drought and the mild winter of 2012 may have contributed to the outbreak.“This shows us how unpredictable West Nile can be, and how we always need to remain vigilant in looking for it, especially early on in the season so that it can be prevented,” Murray said.
Steve Campbell, 817-390-7981 Twitter: @stevecamp