on august 3 , 2012 , fever developed in a previously healthy 63-year - old woman who lived in chuncheon - si , gangwon province , south korea ; the same day , she noticed a lump on the left side of her neck .
she visited a local clinic , and ciprofloxacin and ceftriaxone were started on the first day of illness .
the patient reported that , 2 weeks before her fever started , she noticed an insect bite on her neck while she was working on a crop farm in hwacheon - gun , gangwon province ( in the northernmost part of south korea ) .
she did not recall having contact with any domestic animals on the farm and had no history of travel outside south korea in the month before illness onset .   on the third day of her illness , she began having watery diarrhea , 6 times per day .
on the fourth day of the illness , thrombocytopenia and leukopenia were recorded at the local clinic ( table ) .
a computed tomography scan of the neck showed an enlarged ( 1.6 cm ) , necrotic lymph node .
multiple lymph nodes on the left cervical and left axillary areas were also swollen . on the sixth day , the patient was transferred to seoul national university hospital . * day 1 was the onset day of the illness .
platelets were transfused on day 7 and day 9 , and fresh frozen plasma was transfused on day 9 and day 10 .
creatinine kinase - mb levels were 7 , 5 , 25.7 , 117.5 and 186.2 ng / ml on days 6 , 7 , 8 , 9 , and 10 , respectively ( reference range 0.66.3 ng / ml ) .
na , not available ; ast , aspartate aminotransferase ; alt , alanine aminotransferase ; ldh , lactate dehydrogenase ; aptt , activated partial prothromboplastin time ; inr , international normalized ratio . at admission to the hospital , the patient was febrile but alert .
her temperature was 38.7c , blood pressure 126/70 mm hg , heart rate 86 beats per minute , and oxygen saturation 92% on room air .
her face was puffy , with a sunburned appearance , and both conjunctivae were congested .
the insect bite site on her posterior neck was swollen and erythematous , and the draining cervical lymph node was enlarged .
laboratory test results showed pancytopenia and elevated serum aminotransferase levels ; prothrombin and activated partial thromboplastin times were normal , but fibrinogen level was decreased ( table ) .
a urine dipstick test showed albuminuria ( + + + ) , and microscopic examination of the urine revealed > 100 erythrocytes per high - power field .
test results for antibodies against orientia tsutsugamushi , hantaan virus , and leptospira were negative .
a chest radiograph showed bilateral increased vascular markings , and the plasma level of b - type natriuretic peptide increased to 134 pg / ml ( reference range < 100 pg / ml ) ; these findings suggested cardiac dysfunction .   on the eighth day of her illness ,
a computed tomography scan of the brain showed no evidence of hemorrhage or infarction and no other abnormalities .
on the tenth day of illness ( august 12 , 2012 ) , the patient died of multiple organ failure .
antiviral drugs , corticosteroids , immunosuppressive agents , or intravenous immunoglobulin were not given . because viral infection was suspected but no virus could be identified , an anticoagulated blood sample was obtained from the patient on the eighth day of illness and stored at 70c . when testing for sftsv became available 7 months later , we inoculated monolayers of vero cells with the patient s blood sample and cultured the cells at 37c in a 5% carbon dioxide atmosphere .
the culture supernatant was also used to inoculate dh82 cells when the cell line became available ; 5 days after the inoculation , we observed a cytopathic effect of sftsv in dh82 cells .
the sftsv - infected vero cell monolayer was fixed according to described methods ( 11 ) and cut on ultramicrotome ( rmc mt - xl ) at 65 nm .
ultrathin sections were stained with saturated 4% uranyl acetate and 4% lead citrate before examination with a transmission electron microscope ( hitachi-7100 ; hitachi high - technologies , ibaraki , japan ) at 75 kv ( figure 1 ) .
transmission electron microscopy image of vero cells infected with severe fever with thrombocytopenia syndrome virus ( arrows ) .
rna was extracted from the stored blood and from virus - infected vero cells by using a qiaamp viral rna mini kit ( qiagen , hilden , germany ) .
reverse transcription pcr ( rt - pcr ) was performed to amplify the partial large ( l ) segment of the viral rna from the stored blood to confirm sftsv , as described ( 12 ) .
rt - pcr results were positive , and direct sequencing was done . a blast search ( http://blast.ncbi.nlm.nih.gov/blast.cgi ) showed no sequences from organisms other than sftsv . using the culture supernatant , full lengths of all 3 genome segments ( l , medium [ m ] , and small [ s ] ) were sequenced by rt - pcr and direct sequencing
after polyadenylation of 3 ends of the genomic and complementary rnas , the sequences of the segment ends were obtained by rapid amplification of cdna ends .
the complete sequences of the l , m , and s segments were deposited in genbank ( accession nos .
the l , m , and s segments of the isolate showed 95.8%99.8% , 94.1%99.9% , and 94.8%99.7% identity , respectively , to previously reported sftsv sequences .
we also constructed a phylogenetic tree by the neighbor - joining method using rna - dependent rna polymerase gene nucleic acid sequences to compare the isolate we obtained to representative sftsv strains from china and japan ; the isolate and the other strains were closely related ( 95.9%99.9% sequence relatedness ) but not identical ( figure 2 ) .
phylogenetic tree for the rna - dependent rna polymerase ( rdrp ) gene sequences of the large segment of an isolate obtained from a patient in south korea who died of an illness retrospectively identified as severe fever with thrombocytopenia syndrome ( sfts ) ( black dot ) compared with representative sfts virus strains from china and japan .
the tree was constructed on the basis of the nucleic acid sequences of the rdrp genes by using the neighbor - joining method .
we confirmed a case of sfts in south korea in 2012 by isolation of sftsv from a stored blood sample collected shortly before the patient s death .
the patient had a history of an insect bite while working on a crop farm in hwacheon - gun , gangwon province , the northernmost part of south korea .
phylogenetic analysis of the rna - dependent rna polymerase gene showed that our virus isolate was closely related to sftsv strains reported from china and japan .  
as of july 5 , 2013 , the korea centers for disease control and prevention had confirmed 13 cases of sfts by rt - pcr ; of these patients , 8 were dead and 5 alive ( 13 ) . except for our patient , who died in 2012 , all cases occurred during 2013 .
 we report a retrospectively identified fatal case of severe fever with thrombocytopenia syndrome ( sfts ) in south korea from 2012 . 
 sfts virus was isolated from the stored blood of the patient . 
 phylogenetic analysis revealed this isolate was closely related to sfts virus strains from china and japan . 
The Study
Conclusions