1 Introduction
Severe fever with thrombocytopenia syndrome (SFTS) is a new acute
infectious disease caused by the severe fever with thrombocytopenia
syndrome virus (SFTSV)
(Yu
et al., 2011)belonging to a a novel phlebovirus (SFTS virus, SFTSV) in
the family Phenuiviridae of the order Bunyavirales (Li et
al., 2019). It was first reported in 2009 in the rural areas of the
Hubei and Henan Provinces in Central China, and the population is
generally susceptible. Since then, the incidence of SFTS has been
successively reported in more than 10 provinces and cities in
China(Zhang et al., 2013), and its epidemic area has a tendency to
spread. The disease is also widely distributed in South Korea (Denic et
al., 2011; Yun et al., 2016) and Japan(Takahashi et al., 2014), and
cases of SFTS have also been reported in the United States (McMullan et
al., 2012; Muehlenbachs et al., 2014). The main clinical manifestations
of the disease are high fever, anorexia, muscle pain, chills,
lymphadenopathy, leukopenia, thrombocytopenia, and multiple organ
failure (Sun et al., 2019). Severe cases can lead to death.
SFTSV is an arbovirus mainly carried by ticks(Liu et al., 2012). The
SFTSV virus genome is composed of three independent gene segments: L
segment (6,368 bp; encodes the RNA-dependent RNA polymerase), M segment
(3,378 bp; encodes the membrane protein precursor), and the ambisense S
segment (1,744 bp; encodes the non-structural S protein and nucleocapsid
protein)(Sun et al., 2014).
Rickettsiosis is a zoonotic
disease mainly spread by ticks and is considered an important global
emerging zoonotic disease (Parola, Paddock, & Raoult, 2005). Humans are
infected by the bite of ticks that carry rickettsial bacteria. Due to
human factors such as lifestyle changes and population rates, and to
environmental factors such as climate change, people have become more
exposed to ticks. Rickettsiosis in humans usually refer to infections
caused by bacterial species belonging to the genus Rickettsia andOrientia . It can be classified into typhus, spotted fever, and
tsutsugamushi disease(Adem, 2019). Clinically, human serum rickettsia
antibodies are used to determine whether the human body is infected withRickettsia . The typical clinical features of these diseases
include: fever, fatigue, anorexia, nausea, headache, and rash, and the
bite of the tick has eschar formation (Liu et al., 2016). These symptoms
usually appear within 1‒2 weeks after infection(Liu et al., 2016). The
clinical manifestations of typhus and SFTS are similar, thereby
complicating diagnosis.
In 2019, our laboratory carried out clinical analysis, laboratory
diagnosis, and traceability studies of SFTSV in suspected cases in the
Infectious Disease Hospital of Shenyang City to characterize SFTSV in
patients in Northeast China. Molecular diagnosis and antibody testing
for Rickettsia were also performed to determine the rates ofRickettsia coinfection with other tick-borne diseases, especially
with SFTSV. The results we present here provide insights into the
characteristics of SFTSV in Northeast China. Further, our findings can
guide clinicians in the diagnosis of tick-borne diseases.