Clinical features and factors associated with severity and fatality among patients with severe fever with thrombocytopenia syndrome Bunyavirus infection in Northeast China

Abstract

Background: In 2009, severe fever with thrombocytopenia syndrome virus (SFTSV) was identified as a novel member of the genus phlebovirus in the Bunyaviridae family in China. The detailed clinical features of cases with SFTSV infection have not been well described, and the risk factors for severity among patients and fatality among severe patients remain to be determined.

Methodology/principal findings: Clinical and laboratory features of 115 hospitalized patients with SFTSV infection during the period from June 2010 to December 2011 in Northeast China were retrospectively reviewed. We assessed the risk factors associated with severity in confirmed cases and fatality in severe cases by multivariate analysis. One hundred and three (89.6%) of 115 patients presented with multiple organ dysfunction, and 22 (19.1%) of 115 proceeded to the stage of life threatening multiple organ failure. Of the 115 patients, 14 fatalities (12.2%) were reported. Multivariate analysis demonstrated that the independent predictors of risk for severity were: albumin ≤ 30 g/l (OR, 8.09; 95% CI, 2.58-25.32), APTT ≥ 66 seconds (OR, 14.28; 95% CI, 3.28-62.24), sodium ≤ 130 mmol/l (OR, 5.44; 95% CI, 1.38-21.40), and presence of neurological manifestations (OR, 7.70; 95% CI, 1.91-31.12). Among patients with severe disease, presence of acute lung injury/acute respiratory distress syndrome (HR, 4.59; 95% CI, 1.48-14.19) and disseminated intravascular coagulation (HR, 4.24; 95% CI, 1.38-13.03) were independently associated with fatality.

Conclusions/significance: SFTSV infection may present with more severe symptoms and laboratory abnormalities than hitherto reported. Due to infection with a novel bunyavirus, the patients may sufferer multiple organ dysfunction and die of multiple organ failure. In the clinical assessment of any case of SFTS, independent factors relating to prognosis need to be taken into account by clinicians.

Figure 1. The epidemic curve of cases of SFTSV infection, by weekly periods of symptom onset, starting on June 2010 and continuing through December 2011.

Figure 2. Brain magnetic resonance imaging of a 39-year old patient with encephalitis and acute flaccid paralysis due to SFTSV infection.

A. Axial T₁-weighted image shows hypointense lesion in the right frontoparietal lobes. B. Axial T₂-weighted image shows the frontoparietal lesion is hyperintense with gyral swelling. C. Axial Flair sequence image shows the lesion is hyperintense with some isointense dots inside. D. Contrast-enhanced T₁-weighted image shows marked dot-like enhancement in the lesion.