Date Published: July 5, 2017
Publisher: Public Library of Science
Author(s): Jianli Hu, Zhifeng Li, Lei Hong, Changjun Bao, Zhong Zhang, Hongying Zhang, Hao He, Xiaochen Wang, Wendong Liu, Zhihang Peng, Limin Shi, Fengcai Zhu, Xue-Jie Yu.
To identify specific clinical and epidemiological parameters for clinical diagnosis of SFTSV infection with relatively higher accuracy.
231 suspected cases of SFTS were reported by various medical institutions from 2011 to 2013 in Jiangsu Province, China. They were followed with SFTSV diagnosis tests and interview-administered questionnaires about demographic characteristics, clinical symptoms and epidemiological exposure factors. Univariate and multivariable logistic regression analysis were used to examine the diagnostic value of these parameters.
SFTSV infection occurred only from April to October annually and usually in hilly areas of specific regions. Three prediction models of SFTSV infection were constructed. Model 3 with clinical and epidemiological parameters combined the benefits of both Model 1and Model 2, which was optimal and had an overall accuracy of 80.2%. Independent indicators for clinical diagnosis of SFTSV infection in Model 3 were as follows: lymphadenopathy (P = 0.01), leucopenia (P<0.01), age >50 years (P = 0.01), tick bites (P<0.01), raising domestic animals in the residential areas (P<0.01) and farming (P = 0.03). Our results show that using a combination of clinical and epidemiological parameters may be a feasible strategy to provide preliminary fast diagnosis as differentiating SFTSV infection from SFTS-like diseases, thus reducing the risk of misdiagnosis.
Severe fever with thrombocytopenia syndrome (SFTS) is an emerging life-threating infectious disease, which might have emerged as early as 2005 in Jiangsu Province, Anhui Province, and Hubei Province but was first identified to associate with a novel bunyavirus infection in 2009 . The novel bunyavirus belongs to phlebovirus in the family Bunyaviridae and is officially named as severe fever with thrombocytopenia syndrome bunyavirus (SFTSV). Ticks, especially Haemaphysalis longicornis, are considered as the main vectors [2, 3]. So far more than 2000 cases were reported from at least 16 provinces in China . SFTS cases were confirmed in Japan and Korea in 2013 [5, 6]. In the United States, two SFTS-like cases were identified in Missouri in 2012 which was caused by Heartland virus, a novel Phlebvirus which was highly homologous with SFTSV . The case fatality varied geographically and temporally from around 10 percent to about 50 percent. The SFTSV can transmit person to person via contact with blood or bloody cremation of patients, similar to Ebola virus [8–10]. No effective vaccine is available at present. Studies have shown that symptomatic and supportive treatment in an early stage of SFTS can reduce the case fatality greatly [11, 12].
SFTS is an emerging tick-borne infectious disease, which has caused comprehensive public health concerns due to its expanding epidemic areas, the capability of human-to-human transmission and a high case fatality rate . The clinical symptoms of SFTS are nonspecific and consistent with many infectious pathogens including bacteria and viruses. It should be mentioned that Anaplasma phagocytophilum was considered to be the causative agent of SFTS in China before the discovery of SFTSV in 2010, because patients with human granulocytic anaplasmos is also presented fever, thrombocytopenia and leucopenia [1, 15]. In fact, in most cases viral laboratory confirmation might not always be available due to unaffordability of test kits, lack of instruments and shortage of trained laboratory technicians in rural areas. At present, SFTS misdiagnosis is very common, posing a challenge both to clinicians and public health officials. On the one hand, our findings also disclosed the problem of SFTS misdiagnosis, that 38.5% of 231 suspected SFTS cases reported by medical institutions in Jiangsu Province from 2011 to 2013, were positive for SFTSV. On the other hand, the median time from illness onset to confirmation was 8.5 days in our study, which suggested that clinicians fail to make the timely diagnosis at present. Therefore, we summarized the first attempt to identify clinical and epidemiological parameters as useful indicators for clinical diagnosis of SFTSV infection, which could provide preliminary fast diagnosis as differentiating SFTSV infection from SFTS-like diseases, thus reduce the risk of misdiagnosis.