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Severe fever with thrombocytopenia syndrome virus

Authors
Hideki Ebihara, PhD
Heinz Feldmann, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Elinor L Baron, MD, DTMH

INTRODUCTION

Severe fever with thrombocytopenia syndrome (SFTS), also known as fever, thrombocytopenia, and leukopenia syndrome (FTLS), is an emerging infectious zoonosis in China, Japan, and South Korea [1]. The causative agent is commonly designated SFTS virus (SFTSV), a newly identified bunyavirus, which appears to be carried by ticks (ie, Haemaphysalis longicornis). The disease is remarkably similar to viral hemorrhagic fevers with a characteristic thrombocytopenia. Heartland virus, isolated from patients in the United States, is a closely related but distinct virus that causes a milder clinical syndrome [2]. There is no treatment or vaccine available.

MICROBIOLOGY

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a new member of the genus Phlebovirus in the family Bunyaviridae [3-5]. The closest relative is Bhanja virus, a tick-borne human pathogenic phlebovirus that causes febrile illness and meningitis [6]. Bunyaviruses are largely spherical, enveloped particles with a diameter of 80 to 120 nm. Particles carry three genomic segments designated large (L), medium (M), and small (S).

The L segment encodes the RNA-dependent RNA polymerase (RdRP), the M segment the glycoproteins Gn and Gc, and the S segment the nucleoprotein (N) and a nonstructural protein (NSs) using an ambisense coding strategy [7]. The N protein encapsidates the genomic RNA; this complex is further associated with the L protein and forms the active transcriptase/replicase complex. The Gn and Gc glycoproteins form a heterodimer and shape the spikes on the surface of the virion. The glycoproteins mediate receptor binding and virus entry and are the target for neutralizing humoral immune responses [7].

The C-type lectin, DC-SIGN, has been identified as one of the factors for SFTSV attachment and entry into cells [8]. The NSs protein serves as a type-I interferon antagonist that suppresses activation of innate immune responses via the IPS-1/IRF-3 and NF-kappaB pathways.

EPIDEMIOLOGY

In 2007, a new disease was recognized in the Huaiyangshan mountain range in China with a case fatality rate of 30 percent [3-5,9]. The disease was termed severe fever with thrombocytopenia syndrome (SFTS) or fever, thrombocytopenia, and leukopenia syndrome (FTLS) [3-5]. A new virus, designated SFTS virus (SFTSV), was isolated from patient blood.

      

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Literature review current through: Nov 2016. | This topic last updated: Thu Mar 31 00:00:00 GMT 2016.
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