Novel thogotovirus associated with febrile illness and death, United States, 2014

Abstract

A previously healthy man from eastern Kansas, USA, sought medical care in late spring because of a history of tick bite, fever, and fatigue. The patient had thrombocytopenia and leukopenia and was given doxycycline for a presumed tickborne illness. His condition did not improve. Multiorgan failure developed, and he died 11 days after illness onset from cardiopulmonary arrest. Molecular and serologic testing results for known tickborne pathogens were negative. However, testing of a specimen for antibodies against Heartland virus by using plaque reduction neutralization indicated the presence of another virus. Next-generation sequencing and phylogenetic analysis identified the virus as a novel member of the genus Thogotovirus.

Keywords: Bourbon virus; Heartland virus; Kansas; Thogotovirus; United States; death; febrile illness; high-throughput nucleotide sequencing; neutralization tests; viruses.

Figure 1

Plaque reduction neutralization test of patient sample for Heartland virus, showing images of the same well obtained days 6, 7, and 8 postinoculation at a dilution of 1:20. Arrows with single heads indicate appearance of a novel virus plaque beginning at day 6. Arrows with double heads indicate development of a typical Heartland virus plaque, apparent on day 7 and more evident on day 8, generated from a control strain added to each well in defined quantities to identify Heartland virus–specific antibodies in the patient sample.

Figure 2

Electron microscopic images of novel Thogotovirus isolate. Filamentous (A) and spherical (B) virus particles with distinct surface projection are visible in culture supernatant that was fixed in 2.5% paraformaldehyde. Thin-section specimens (C and D), fixed in 2.5% glutaraldehyde, show numerous extracellular virions with slices through strands of viral nucleocapsids. Arrows indicate virus particles that have been endocytosed. Scale bars indicate 100 nm.

Figure 3

Phylogenies of deduced amino acid sequences of representative genes of Bourbon virus in comparison to homologous sequences of selected orthomyxoviruses. A neighbor-joining method was used for inference of each phylogeny with 2,000 replicates for bootstrap testing. Values at nodes are bootstrap values. A) PA polymerase subunit (segment 3). B) Nucleocapsid protein (segment 5). C) Membrane protein (segment 6). GenBank accession numbers appear next to taxon names. Scale bars indicate number of amino acid substitutions per site.