Severe Fever with Thrombocytopenia Syndrome, Japan, 2013-2017

Abstract

We conducted an epidemiologic study of severe fever with thrombocytopenia syndrome (SFTS) in Japan during 2013-2017. Of 303 cases reported during that period, 133 (44%) were included in this study. The median time between onset of illness and diagnosis of SFTS shortened, from 11.5 to 3.0 days, but the case-fatality rate remained high, at 27%. In 64 patients (48%), a close contact with companion animals was reported within 2 weeks of disease onset. Of these 64 patients, 40 were surveyed further, and we confirmed that 3 had direct contact with body fluids of ill companion animals; 2 had direct contact with the saliva of an ill feral cat or pet dog. These patients reported no history of tick bite, suggesting that ill companion animals might be a source of SFTS virus transmission. Direct contact with the body fluids of ill companion animals should be avoided.

Keywords: Huaiyangshan banyangvirus; Japan; Phenuiviridae; SFTS; SFTSV; companion animal; epidemiology; severe fever with thrombocytopenia syndrome; severe fever with thrombocytopenia syndrome virus; tickborne diseases; vector-borne infections; viruses; zoonoses.

Figure 1

Flow diagram of epidemiologic study of 133 patients with severe fever with thrombocytopenia syndrome, Japan, March 2013–October 2017. NESID, National Epidemiologic Surveillance of Infectious Disease; SFTS, severe fever with thrombocytopenia syndrome.

Figure 2

Comparison of time between illness onset and confirmed diagnosis in 133 patients with severe fever with thrombocytopenia syndrome, Japan, March 2013–October 2017. We conducted a trend analysis of time from initial visit to diagnosis over the study period by using the Jonkheere–Trapstra test (p<0.01). In the box plots, the bottom boundary of the box indicates the 25th percentile, the line within the box marks the median, and the top boundary of the box indicates the 75th percentile. Whiskers above and below the box indicate the 10th and 90th percentiles.

Figure 3

Annual number and CFRs and Kaplan–Meier survival curve of 133 patients with severe fever with thrombocytopenia syndrome, Japan, March 2013–October 2017. A) Trend analysis of CFRs over the study period by using Spearman rank correlation test (p = 0.285). B) Kaplan-Meier curve of 133 patients with severe fever with thrombocytopenia syndrome within 30 days after illness onset. CFR, case-fatality rate.