Severe fever with thrombocytopenia syndrome virus, South Korea, 2013

Abstract

During 2013, severe fever with thrombocytopenia syndrome was diagnosed in 35 persons in South Korea. Environmental temperature probably affected the monthly and regional distribution of case-patients within the country. Phylogenetic analysis indicated that the isolates from Korea were closely related to isolates from China and Japan.

Figure 1

Isolation of severe fever with thrombocytopenia syndrome virus (SFTSV) from case-patients, South Korea, 2013. A, B) Indirect immunofluorescent features of Vero E6 cells primed with SFTSV N protein monoclonal antibody and reacted with fluoresce in isothiocyanateconjugated anti-mouse IgG. B) Transmission electron microscopy image of Vero E6 cells infected with SFTSV. Scale bar indicates 500 nm.

Figure 2

A and B) Phylogenetic analysis of SFTSV Korea isolates based on the partial medium (M) and small (S) segment sequences. The phylogenetic trees were generated by MEGA version 5.2 software (http://www.megasoftware.net/) from aligned nucleotide sequences of 16 isolates of phleboviruses, including the identified SFTSV. Heartland virus was used as outgroup. M and S partial nucleotide sequences of SFTSV Korea isolates were compared with homologous sequences of previously characterized SFTSVs. Sequences were analyzed by the neighbor-joining method based on the maximum composite likelihood model. The minimal length trees shown were supported as the majority rule consensus trees in 5,000 replicates. The bootstrap replicates supporting each node are indicated. Korea isolates are marked with black circles. Scale bar indicates nucleotide substitutions per site.

Figure 3

Seasonal (A) and geographic (B) distribution of casepatients with severe fever with thrombocytopenia syndrome (SFTS), South Korea, 2013. A) White and black bars indicate the numbers of total and deceased SFTS patients, respectively, in the indicated months. B) Black circles indicate the approximate residential regions of 35 SFTS case-patients in 2013 in South Korea. GG, Gyeonggi Province; GW, Gangwon Province; CB, Chungcheongbuk Province; CN, Chungcheongnam Province; GB, Gyeongsangbuk Province; GN, Gyeongsangnam Province; JB, Jeollabuk Province; JN, Jeollanam Province; JJ, Jeju special autonomous Province.