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Severe fever with thrombocytopenia syndrome virus

Author
Myoung-don Oh, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Elinor L Baron, MD, DTMH

INTRODUCTION

Severe fever with thrombocytopenia syndrome (SFTS) 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 that appears to be carried by ticks (ie, Haemaphysalis longicornis).

MICROBIOLOGY

Severe fever with thrombocytopenia syndrome (SFTS) virus (SFTSV) is a new member of the genus Phlebovirus in the family Bunyaviridae [2-4]. The closest relative is Bhanja virus, a tickborne human pathogenic phlebovirus that causes febrile illness and meningitis [5]. 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 [6]. The N protein encapsulates 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 [6].

The C-type lectin, DC-SIGN, has been identified as one of the factors for SFTSV attachment and entry into cells [7]. 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.

SFTSV has been classified into Chinese and Japanese lineages, consistent with the geographical distribution; the two lineages are further divided into six and four sub-lineages, respectively [8]. The SFTSV strains isolated in South Korea are clustered in the Japanese lineage [9].

          

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Literature review current through: Aug 2017. | This topic last updated: May 04, 2017.
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