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Department of Internal MedicineDivision of Infectious Diseases

Dear Dr. Perkins,

Infectious Disease physicians practicing in Dallas County and caring for patients with severe West Nile virus(WNV) disease met on August 3, 2012 at the Dallas County Health Department. We heard up-to-dateinformation about the epidemiology of the WNV epidemic in Dallas County. This outbreak has rapidly evolved

over the past weeks to be the largest WNV outbreak currently in the United States. With 123 cases of WNV and6 deaths occurring in our County barely halfway through the season, this will likely become one of the largesturban WNV epidemics in the recorded history of the virus.

The patients with severe WNV disease that we are currently caring for are very ill, and often in intensive careunits. Even those who do not die from their illnesses will have a prolonged and difficult convalescence and

rehabilitative course. Our deep concern for our patients and the high numbers of persons affected within ashort few weeks prompt the writing of this letter.

We applaud the activity of the Health Department staff in accumulating and analyzing the epidemiological dataand want to cite particularly persons working in mosquito surveillance and control for their efforts and thechallenging and sometimes dangerous work that they perform. The magnitude and extent of this outbreak,

however, is of an unprecedented nature and represents a once in 50-year medical event. It rivals the 1966Dallas St. Louis encephalitis epidemic, which resulted in 168 cases including 16 deaths.

We want to stress the urgency with which our community needs to apply additional resources to controlling the

mosquitoes which are responsible for spreading this outbreak. The CDC guidelines for such extreme outbreaksinclude control measures like aerial spraying to kill efficaciously adult mosquitoes carrying WNV.1 We commend

the health departments recent request to the State for more physical resources to augment conventionallarviciding and ground-based adulticiding efforts. However, the severity of the current outbreak means thatthere are areas of intense WNV activity, which are not sufficiently responding to conventional ground-sprayingand larvicidal control efforts.

We strongly recommend requesting urgent State and Federal assistance to assess rapidly and implement

enhanced additional mosquito control measures for this large-scale outbreak.2 At this time, as an alternative towidespread use of aerial spraying, we would advocate selective adaptation of aerial applications to specific areaswith highest numbers of ongoing human cases despite usual ground-based control activities. Aerial sprayingcould be conducted of selected areas of the county that demonstrate the most intense viral activity inmosquitoes and humans. The data indicates that a greater concentration of cases is now occurring in parts of

north Dallas County.

Aerial spraying has been scientifically proven to be effective in reducing human illness from WNV. Historically,aerial spraying has been used effectively other outbreak circumstances in the US, including in Dallas in 1966when such spraying successfully reduced mosquito infection rates for St. Louis encephalitis virus, from one in150 mosquitoes being infected to less than one in 50,000 mosquitoes. We would also call attention to theSacramento County California WNV epidemic in 2005 where aerial spraying effectively ended new human

infections in areas which were sprayed, as compared to untreated areas.3 Aerial spraying was also usedsuccessfully in the urban New York City during their 1999 outbreak of WNV.

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We think that the time to act is now and that delaying consideration of stronger aerial control measures will onlylead to more tragic cases of severe illnesses. There have been over 40 new WNV infections per week reportedin Dallas County residents over the past 2 weeks. The typical peak of illnesses in Dallas County occurs in Augustwith a continuing number being reported for several more weeks. The public health risks from WNV this seasonclearly exceed the risks from exposure to mosquito insecticides.4 The economic cost of aerial spraying needs to

be compared to the cost of the continued loss of lives, continued medical intensive care admissions, and thedebilitating loss of function that the anticipated numbers of WNV victims encephalitis will suffer from this

outbreak.

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Respectfully,

Roger Bedimo, MDAssociate Professor VA

Christopher J. Bettacchi, MD

North Texas Infectious Diseases Consultants

Steven Gabe Davis, MD FACP

Dallas ID Associates

Edward L. Goodman, MD, FACP, FIDSA, FSHEATexas Health Presbyterian Hospital of Dallas

Jade Le, MD

Assistant Professor, Infectious Diseases UTSW

James Luby, MDProfessor, Infectious Diseases UTSW

Jane D. Siegel, MDProfessor, Pediatrics UTSW

Donald F. Storey, MD, FACPDallas ID Associates

Parisa Ann Suthun, MDMedical Clinic of North Texas

Paul Southern, MDProfessor, Pathology UTSW

William Sutker, MDNorth Texas Infectious Diseases Consultants

Mark Swancutt, MDInterim Chief, Infectious Diseases UTSW

Marc A. Tribble, MD

Baylor University Medical Center

Gene Voskuhl, MDAIDS Arms

1. Centers for Disease Control and Prevention. Epidemic/Epizootic West Nile Virus in the United States: Guidelines forSurveillance, Prevention, and Control, 2003. http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnvguidelines2003.pdf

2. Texas Department of State Health Services. Response Operating Guidelines: Vector Control2012. (www.dshs.state.tx.us/commprep/response/ROG.aspx)

http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnvguidelines2003.pdfhttp://www.cdc.gov/ncidod/dvbid/westnile/resources/wnvguidelines2003.pdf

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3. Carney RM, Husted S, Jean C, Glaser C, Kramer V. Efficacy of Aerial Spraying of MosquitoAdulticide in Reducing Incidence of West Nile Virus, California, 2005. Emerging InfectiousDiseases. 2008, 14:747-54.

4. Peterson RK, Macedo P, and Davis RS. A Human-Health Risk Assessment for West Nile Virusand Insecticides Used in Mosquito Management. Environmental Health Perspectives. 2006,

114(3):366-372.

5. Schwab, P. Economic Cost of St. Louis Encephalitis Epidemic in Dallas, Texas, 1966. PublicHealth Reports. 1968, 83(1)):860-866.