6 Cases of New Tick-Borne Heartland Virus, CDC Reports

Janis C. Kelly

March 27, 2014

The Centers for Disease Control and Prevention (CDC) has advised healthcare providers to consider Heartland virus testing for patients who have otherwise unexplained fever, leukopenia, and thrombocytopenia and who have tested negative for Ehrlichia and Anaplasma infection or have not responded to doxycycline therapy.

Heartland is a newly identified phlebovirus believed to be transmitted by the Lone Star tick (Amblyomma americanum). The CDC defines Heartland virus infection as fever (≥100.4°F [≥38.0°C]), leukopenia (white blood cell count, <4500 cells/mm3), and thrombocytopenia (platelet count, <150,000/mm3) without a more likely clinical explanation.

Daniel M. Pastula, MD, an Epidemic Intelligence Service officer with the CDC Division of Vector-Borne Diseases, Fort Collins, Colorado, and colleagues describe the 6 new cases of Heartland virus disease in their article, published in the March 28 issue of the Morbidity and Mortality Weekly Report. All of the patients either had viral RNA detected by reverse transcriptase–polymerase chain reaction on blood or tissue or a 4-fold or higher rise in virus-specific plaque reduction neutralization antibody titers between acute and convalescent serum specimens.

The cases occurred in 2012 and 2013 and bring the total number of known cases to 8. The new cases included 5 cases in Missouri and 1 in Tennessee, all in white men older than 50 years. The Tennessee patient is the first known case of Heartland virus disease outside of Missouri.

The patients presented with fever, fatigue, loss of appetite, headache, nausea, and/or muscle pain. Four of the 6 new cases had symptoms severe enough to require hospitalization, and 1 (who had other comorbidities) died.

"All of the patients reported spending several hours per day outside (e.g., working, walking, doing yard work, hunting, or hiking), and five of the six patients reported tick bites in the 14 days preceding their illness onset," the authors write.

Because there is currently no vaccine or treatment for Heartland virus disease, the CDC report emphasized "using insect repellents, wearing long sleeves and pants, avoiding bushy and wooded areas, and performing tick checks after spending time outdoors." Supportive therapies such as intravenous fluids and fever reducers can relieve some Heartland disease symptoms.

Nearly all the newly reported cases were discovered through a study conducted by the Missouri Department of Health and Senior Services and the CDC, which are actively searching for human cases at 6 Missouri hospitals.

CDC studies to date have shown that Heartland virus is carried by Lone Star ticks, which are primarily found in the southeastern and eastern United States. Additional studies seek to confirm whether ticks can spread the virus to people and to learn what other insects or animals may be involved in the transmission cycle. CDC is also looking for Heartland virus in other parts of the country to understand how widely it may be distributed.

"During the past two years, CDC has worked closely with state health departments, hospitals, and many experts from universities and other federal agencies to learn more about Heartland virus," Roger Nasci, PhD, chief of the CDC's Arboviral Diseases Branch said in a CDC news release. "By gathering information about the disease Heartland virus causes, and about how it's spread to people, we hope to better understand the potential impact on the public's health and how we can help protect people from this virus."

The authors have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. 2014;63:270-271. Full text

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