In 2011, a tickborne phlebovirus — so-called severe fever with thrombocytopenia syndrome virus (SFTSV) — was described as a cause of human disease in China. Now, illness closely resembling that caused by SFTSV has been reported in two men in northwestern Missouri.
The two patients had suffered tick bites 5 to 7 days before the onset of a severe febrile illness characterized by fatigue, diarrhea, thrombocytopenia, and leukopenia. Ehrlichiosis was the presumptive diagnosis in each case, but results from laboratory tests (serologic analysis, polymerase chain reaction assay, cell culture) were all negative. The men were hospitalized for 10 and 12 days.
Viral particles were isolated from the patients’ leukocytes in cell culture. Thin-section electron microscopy revealed characteristics of viruses in the Bunyaviridae family. Total RNA was recovered from the infected culture media and subjected to genomic sequencing; the resulting sequences were similar to those of phleboviruses in the Bunyaviridae family. Phylogenetic analysis demonstrated a distinct virus closely related to SFTSV. Enzyme-linked immunosorbent assay testing of serum samples collected from the patients >2 years after illness onset showed high titers of antibodies reactive to the novel virus (dubbed “Heartland” by the researchers).
Comment: Some patients who have been treated for anaplasmosis or ehrlichiosis may have had Heartland virus infection or coinfection. The list of tickborne illnesses in the U.S. and abroad continues to expand, as is evidenced by cases described in this article and other recent reports (JW Infect Dis Mar 16 2011 and Aug 3 2011).