Prevalence and M-fragment gene sequencing of fever with thrombocytopenia syndrome virus in Liaoning province, 2011 – 2017

Objective To examine prevalence characteristics of severe fever with thrombocytopenia syndrome (SFTS) and to analyze genetic distribution and evolution of SFTS virus (SFTSV) in Liaoning province during 2011 – 2017.

Methods We collected the data on all confirmed SFTS cases reported in Liaoning province from January 2011 through 2017 and described the prevalent characteristics of the cases. Five SFTSV strains were randomly selected from all the isolated strains each year and the M-fragment gene sequence of the strains was amplified with reverse transcription-polymerase chain reaction (RT-PCR) and homology analysis was performed using software MEGA 6.0 to construct the relative evolution tree.

Results Totally 438 confirmed SFTS cases were reported in the province during the period; of them, 19 were dead, with a case fatality rate of 4.34%, and 89.95% were aged ≥ 45 years. More cases were reported during the spring and summer season (July to September in a year) and more cases (242 and 144) were reported in Dandong and Dalian municipality. The most (91.32%) of the reported cases were farmers, house workers and unemployed people. The sequence analysis revealed that the nucleotide sequence homology for the 35 isolated SFTSV strains was 92.20% – 100%; both C and J genotypes were observed among the 35 strains and 25 strains were of C2 genomic branch.

Conclusion In Liaoning province between 2011 – 2017, SFTS epidemic showed seasonal and regional distribution; farmers aged 45 years had a higher risk of SFTS; and SFTSV of C genomic subtype was the prevalent strain.